patch, 7 partsrerere: split conflict ID further

rerere.c, rerere.h

diff --git a/rerere.c b/rerere.c
index 9bef24f..a5d8a06 100644
--- a/rerere.c
+++ b/rerere.c
@@ -8,6 +8,7 @@
 #include "ll-merge.h"
 #include "attr.h"
 #include "pathspec.h"
+#include "sha1-lookup.h"
 
 #define RESOLVED 0
 #define PUNTED 1
@@ -22,6 +23,23 @@ static int rerere_autoupdate;
 
 static char *merge_rr_path;
 
+static int rerere_dir_nr;
+static int rerere_dir_alloc;
+
+static struct rerere_dir {
+	unsigned char sha1[20];
+} **rerere_dir;
+
+static void free_rerere_dirs(void)
+{
+	int i;
+	for (i = 0; i < rerere_dir_nr; i++)
+		free(rerere_dir[i]);
+	free(rerere_dir);
+	rerere_dir_nr = rerere_dir_alloc = 0;
+	rerere_dir = NULL;
+}
+
 static void free_rerere_id(struct string_list_item *item)
 {
 	free(item->util);
@@ -29,7 +47,7 @@ static void free_rerere_id(struct string_list_item *item)
 
 static const char *rerere_id_hex(const struct rerere_id *id)
 {
-	return id->hex;
+	return sha1_to_hex(id->collection->sha1);
 }
 
 const char *rerere_path(const struct rerere_id *id, const char *file)
@@ -40,6 +58,37 @@ const char *rerere_path(const struct rerere_id *id, const char *file)
 	return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
 }
 
+static const unsigned char *rerere_dir_sha1(size_t i, void *table)
+{
+	struct rerere_dir **rr_dir = table;
+	return rr_dir[i]->sha1;
+}
+
+static struct rerere_dir *find_rerere_dir(const char *hex)
+{
+	unsigned char sha1[20];
+	struct rerere_dir *rr_dir;
+	int pos;
+
+	if (get_sha1_hex(hex, sha1))
+		return NULL; /* BUG */
+	pos = sha1_pos(sha1, rerere_dir, rerere_dir_nr, rerere_dir_sha1);
+	if (pos < 0) {
+		rr_dir = xmalloc(sizeof(*rr_dir));
+		hashcpy(rr_dir->sha1, sha1);
+		pos = -1 - pos;
+
+		/* Make sure the array is big enough ... */
+		ALLOC_GROW(rerere_dir, rerere_dir_nr + 1, rerere_dir_alloc);
+		/* ... and add it in. */
+		rerere_dir_nr++;
+		memmove(rerere_dir + pos + 1, rerere_dir + pos,
+			(rerere_dir_nr - pos - 1) * sizeof(*rerere_dir));
+		rerere_dir[pos] = rr_dir;
+	}
+	return rerere_dir[pos];
+}
+
 static int has_rerere_resolution(const struct rerere_id *id)
 {
 	struct stat st;
@@ -50,7 +99,7 @@ static int has_rerere_resolution(const struct rerere_id *id)
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
-	strcpy(id->hex, hex);
+	id->collection = find_rerere_dir(hex);
 	return id;
 }
 
@@ -810,12 +859,14 @@ int setup_rerere(struct string_list *merge_rr, int flags)
 int rerere(int flags)
 {
 	struct string_list merge_rr = STRING_LIST_INIT_DUP;
-	int fd;
+	int fd, status;
 
 	fd = setup_rerere(&merge_rr, flags);
 	if (fd < 0)
 		return 0;
-	return do_plain_rerere(&merge_rr, fd);
+	status = do_plain_rerere(&merge_rr, fd);
+	free_rerere_dirs();
+	return status;
 }
 
 static int rerere_forget_one_path(const char *path, struct string_list *rr)
@@ -900,7 +951,7 @@ int rerere_forget(struct pathspec *pathspec)
 static struct rerere_id *dirname_to_id(const char *name)
 {
 	static struct rerere_id id;
-	strcpy(id.hex, name);
+	id.collection = find_rerere_dir(name);
 	return &id;
 }
 
diff --git a/rerere.h b/rerere.h
index ce545d0..faf5a23 100644
--- a/rerere.h
+++ b/rerere.h
@@ -15,8 +15,9 @@ struct pathspec;
  */
 extern void *RERERE_RESOLVED;
 
+struct rerere_dir;
 struct rerere_id {
-	char hex[41];
+	struct rerere_dir *collection;
 };
 
 extern int setup_rerere(struct string_list *, int);

diff --git a/rerere.c b/rerere.c
index a5d8a06..fbdade8 100644
--- a/rerere.c
+++ b/rerere.c
@@ -26,8 +26,11 @@ static char *merge_rr_path;
 static int rerere_dir_nr;
 static int rerere_dir_alloc;
 
+#define RR_HAS_POSTIMAGE 1
+#define RR_HAS_PREIMAGE 2
 static struct rerere_dir {
 	unsigned char sha1[20];
+	unsigned char status;
 } **rerere_dir;
 
 static void free_rerere_dirs(void)
@@ -58,6 +61,27 @@ const char *rerere_path(const struct rerere_id *id, const char *file)
 	return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
 }
 
+static int is_rr_file(const char *name, const char *filename)
+{
+	return !strcmp(name, filename);
+}
+
+static void scan_rerere_dir(struct rerere_dir *rr_dir)
+{
+	struct dirent *de;
+	DIR *dir = opendir(git_path("rr-cache/%s", sha1_to_hex(rr_dir->sha1)));
+
+	if (!dir)
+		return;
+	while ((de = readdir(dir)) != NULL) {
+		if (is_rr_file(de->d_name, "postimage"))
+			rr_dir->status |= RR_HAS_POSTIMAGE;
+		else if (is_rr_file(de->d_name, "preimage"))
+			rr_dir->status |= RR_HAS_PREIMAGE;
+	}
+	closedir(dir);
+}
+
 static const unsigned char *rerere_dir_sha1(size_t i, void *table)
 {
 	struct rerere_dir **rr_dir = table;
@@ -76,6 +100,7 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 	if (pos < 0) {
 		rr_dir = xmalloc(sizeof(*rr_dir));
 		hashcpy(rr_dir->sha1, sha1);
+		rr_dir->status = 0;
 		pos = -1 - pos;
 
 		/* Make sure the array is big enough ... */
@@ -85,15 +110,14 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 		memmove(rerere_dir + pos + 1, rerere_dir + pos,
 			(rerere_dir_nr - pos - 1) * sizeof(*rerere_dir));
 		rerere_dir[pos] = rr_dir;
+		scan_rerere_dir(rr_dir);
 	}
 	return rerere_dir[pos];
 }
 
 static int has_rerere_resolution(const struct rerere_id *id)
 {
-	struct stat st;
-
-	return !stat(rerere_path(id, "postimage"), &st);
+	return (id->collection->status & RR_HAS_POSTIMAGE);
 }
 
 static struct rerere_id *new_rerere_id_hex(char *hex)
@@ -737,6 +761,7 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 	} else if (!handle_file(path, NULL, NULL)) {
 		/* The user has resolved it. */
 		copy_file(rerere_path(id, "postimage"), path, 0666);
+		id->collection->status |= RR_HAS_POSTIMAGE;
 		fprintf(stderr, "Recorded resolution for '%s'.\n", path);
 	} else {
 		return;
@@ -797,6 +822,7 @@ static int do_plain_rerere(struct string_list *rr, int fd)
 		 * normalized contents to the "preimage" file.
 		 */
 		handle_file(path, NULL, rerere_path(id, "preimage"));
+		id->collection->status |= RR_HAS_PREIMAGE;
 		fprintf(stderr, "Recorded preimage for '%s'\n", path);
 	}
 

rerere.c, t/t4200-rerere.sh

diff --git a/rerere.c b/rerere.c
index fbdade8..a1e2963 100644
--- a/rerere.c
+++ b/rerere.c
@@ -117,7 +117,9 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 
 static int has_rerere_resolution(const struct rerere_id *id)
 {
-	return (id->collection->status & RR_HAS_POSTIMAGE);
+	const int both = RR_HAS_POSTIMAGE|RR_HAS_PREIMAGE;
+
+	return ((id->collection->status & both) == both);
 }
 
 static struct rerere_id *new_rerere_id_hex(char *hex)
@@ -806,24 +808,30 @@ static int do_plain_rerere(struct string_list *rr, int fd)
 		string_list_insert(rr, path)->util = id;
 
 		/*
-		 * If the directory does not exist, create
-		 * it.  mkdir_in_gitdir() will fail with
-		 * EEXIST if there already is one.
-		 *
-		 * NEEDSWORK: make sure "gc" does not remove
-		 * preimage without removing the directory.
+		 * Ensure that the directory exists.
+		 * mkdir_in_gitdir() will fail with EEXIST if there
+		 * already is one.
 		 */
-		if (mkdir_in_gitdir(rerere_path(id, NULL)))
-			continue;
+		if (mkdir_in_gitdir(rerere_path(id, NULL)) &&
+		    errno != EEXIST)
+			continue; /* NEEDSWORK: perhaps we should die? */
 
-		/*
-		 * We are the first to encounter this
-		 * conflict.  Ask handle_file() to write the
-		 * normalized contents to the "preimage" file.
-		 */
-		handle_file(path, NULL, rerere_path(id, "preimage"));
-		id->collection->status |= RR_HAS_PREIMAGE;
-		fprintf(stderr, "Recorded preimage for '%s'\n", path);
+		if (id->collection->status & RR_HAS_PREIMAGE) {
+			;
+		} else {
+			/*
+			 * We are the first to encounter this
+			 * conflict.  Ask handle_file() to write the
+			 * normalized contents to the "preimage" file.
+			 *
+			 * NEEDSWORK: what should happen if we had a
+			 * leftover postimage that is totally
+			 * unrelated?  Perhaps we should unlink it?
+			 */
+			handle_file(path, NULL, rerere_path(id, "preimage"));
+			id->collection->status |= RR_HAS_PREIMAGE;
+			fprintf(stderr, "Recorded preimage for '%s'\n", path);
+		}
 	}
 
 	for (i = 0; i < rr->nr; i++)
diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index ed9c91e..52a8e09 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -184,12 +184,28 @@ test_expect_success 'rerere updates postimage timestamp' '
 '
 
 test_expect_success 'rerere clear' '
-	rm $rr/postimage &&
+	cp $rr/preimage .git/pre-saved &&
+	mv $rr/postimage .git/post-saved &&
 	echo "$sha1	a1" | perl -pe "y/\012/\000/" >.git/MERGE_RR &&
 	git rerere clear &&
 	! test -d $rr
 '
 
+test_expect_success 'leftover directory' '
+	git reset --hard &&
+	mkdir -p $rr &&
+	test_must_fail git merge first &&
+	test -f $rr/preimage
+'
+
+test_expect_success 'missing preimage' '
+	git reset --hard &&
+	mkdir -p $rr &&
+	cp .git/post-saved $rr/postimage &&
+	test_must_fail git merge first &&
+	test -f $rr/preimage
+'
+
 test_expect_success 'set up for garbage collection tests' '
 	mkdir -p $rr &&
 	echo Hello >$rr/preimage &&

diff --git a/rerere.c b/rerere.c
index a1e2963..c0482b8 100644
--- a/rerere.c
+++ b/rerere.c
@@ -122,6 +122,11 @@ static int has_rerere_resolution(const struct rerere_id *id)
 	return ((id->collection->status & both) == both);
 }
 
+static int has_rerere_preimage(const struct rerere_id *id)
+{
+	return (id->collection->status & RR_HAS_PREIMAGE);
+}
+
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
@@ -749,8 +754,24 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 	const char *path = rr_item->string;
 	const struct rerere_id *id = rr_item->util;
 
-	/* Is there a recorded resolution we could attempt to apply? */
-	if (has_rerere_resolution(id)) {
+	if (!has_rerere_preimage(id)) {
+		/*
+		 * We are the first to encounter this conflict.  Ask
+		 * handle_file() to write the normalized contents to
+		 * the "preimage" file.
+		 */
+		handle_file(path, NULL, rerere_path(id, "preimage"));
+		if (id->collection->status & RR_HAS_POSTIMAGE) {
+			const char *path = rerere_path(id, "postimage");
+			if (unlink(path))
+				die_errno("cannot unlink stray '%s'", path);
+			id->collection->status &= ~RR_HAS_PREIMAGE;
+		}
+		id->collection->status |= RR_HAS_PREIMAGE;
+		fprintf(stderr, "Recorded preimage for '%s'\n", path);
+		return;
+	} else if (has_rerere_resolution(id)) {
+		/* Is there a recorded resolution we could attempt to apply? */
 		if (merge(id, path))
 			return; /* failed to replay */
 
@@ -807,31 +828,8 @@ static int do_plain_rerere(struct string_list *rr, int fd)
 		id = new_rerere_id(sha1);
 		string_list_insert(rr, path)->util = id;
 
-		/*
-		 * Ensure that the directory exists.
-		 * mkdir_in_gitdir() will fail with EEXIST if there
-		 * already is one.
-		 */
-		if (mkdir_in_gitdir(rerere_path(id, NULL)) &&
-		    errno != EEXIST)
-			continue; /* NEEDSWORK: perhaps we should die? */
-
-		if (id->collection->status & RR_HAS_PREIMAGE) {
-			;
-		} else {
-			/*
-			 * We are the first to encounter this
-			 * conflict.  Ask handle_file() to write the
-			 * normalized contents to the "preimage" file.
-			 *
-			 * NEEDSWORK: what should happen if we had a
-			 * leftover postimage that is totally
-			 * unrelated?  Perhaps we should unlink it?
-			 */
-			handle_file(path, NULL, rerere_path(id, "preimage"));
-			id->collection->status |= RR_HAS_PREIMAGE;
-			fprintf(stderr, "Recorded preimage for '%s'\n", path);
-		}
+		/* Ensure that the directory exists. */
+		mkdir_in_gitdir(rerere_path(id, NULL));
 	}
 
 	for (i = 0; i < rr->nr; i++)

rerere.c, rerere.h

diff --git a/rerere.c b/rerere.c
index c0482b8..f674461 100644
--- a/rerere.c
+++ b/rerere.c
@@ -30,14 +30,17 @@ static int rerere_dir_alloc;
 #define RR_HAS_PREIMAGE 2
 static struct rerere_dir {
 	unsigned char sha1[20];
-	unsigned char status;
+	int status_alloc, status_nr;
+	unsigned char *status;
 } **rerere_dir;
 
 static void free_rerere_dirs(void)
 {
 	int i;
-	for (i = 0; i < rerere_dir_nr; i++)
+	for (i = 0; i < rerere_dir_nr; i++) {
+		free(rerere_dir[i]->status);
 		free(rerere_dir[i]);
+	}
 	free(rerere_dir);
 	rerere_dir_nr = rerere_dir_alloc = 0;
 	rerere_dir = NULL;
@@ -53,17 +56,59 @@ static const char *rerere_id_hex(const struct rerere_id *id)
 	return sha1_to_hex(id->collection->sha1);
 }
 
+static void fit_variant(struct rerere_dir *rr_dir, int variant)
+{
+	variant++;
+	ALLOC_GROW(rr_dir->status, variant, rr_dir->status_alloc);
+	if (rr_dir->status_nr < variant) {
+		memset(rr_dir->status + rr_dir->status_nr,
+		       '\0', variant - rr_dir->status_nr);
+		rr_dir->status_nr = variant;
+	}
+}
+
+static void assign_variant(struct rerere_id *id)
+{
+	int variant;
+	struct rerere_dir *rr_dir = id->collection;
+
+	variant = id->variant;
+	if (variant < 0) {
+		variant = 0; /* for now */
+	}
+	fit_variant(rr_dir, variant);
+	id->variant = variant;
+}
+
 const char *rerere_path(const struct rerere_id *id, const char *file)
 {
 	if (!file)
 		return git_path("rr-cache/%s", rerere_id_hex(id));
 
-	return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
+	if (id->variant <= 0)
+		return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
+
+	return git_path("rr-cache/%s/%s.%d",
+			rerere_id_hex(id), file, id->variant);
 }
 
-static int is_rr_file(const char *name, const char *filename)
+static int is_rr_file(const char *name, const char *filename, int *variant)
 {
-	return !strcmp(name, filename);
+	const char *suffix;
+	char *ep;
+
+	if (!strcmp(name, filename)) {
+		*variant = 0;
+		return 1;
+	}
+	if (!skip_prefix(name, filename, &suffix) || *suffix != '.')
+		return 0;
+
+	errno = 0;
+	*variant = strtol(suffix + 1, &ep, 10);
+	if (errno || *ep)
+		return 0;
+	return 1;
 }
 
 static void scan_rerere_dir(struct rerere_dir *rr_dir)
@@ -74,10 +119,15 @@ static void scan_rerere_dir(struct rerere_dir *rr_dir)
 	if (!dir)
 		return;
 	while ((de = readdir(dir)) != NULL) {
-		if (is_rr_file(de->d_name, "postimage"))
-			rr_dir->status |= RR_HAS_POSTIMAGE;
-		else if (is_rr_file(de->d_name, "preimage"))
-			rr_dir->status |= RR_HAS_PREIMAGE;
+		int variant;
+
+		if (is_rr_file(de->d_name, "postimage", &variant)) {
+			fit_variant(rr_dir, variant);
+			rr_dir->status[variant] |= RR_HAS_POSTIMAGE;
+		} else if (is_rr_file(de->d_name, "preimage", &variant)) {
+			fit_variant(rr_dir, variant);
+			rr_dir->status[variant] |= RR_HAS_PREIMAGE;
+		}
 	}
 	closedir(dir);
 }
@@ -100,7 +150,9 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 	if (pos < 0) {
 		rr_dir = xmalloc(sizeof(*rr_dir));
 		hashcpy(rr_dir->sha1, sha1);
-		rr_dir->status = 0;
+		rr_dir->status = NULL;
+		rr_dir->status_nr = 0;
+		rr_dir->status_alloc = 0;
 		pos = -1 - pos;
 
 		/* Make sure the array is big enough ... */
@@ -118,19 +170,27 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 static int has_rerere_resolution(const struct rerere_id *id)
 {
 	const int both = RR_HAS_POSTIMAGE|RR_HAS_PREIMAGE;
+	int variant = id->variant;
 
-	return ((id->collection->status & both) == both);
+	if (variant < 0)
+		return 0;
+	return ((id->collection->status[variant] & both) == both);
 }
 
 static int has_rerere_preimage(const struct rerere_id *id)
 {
-	return (id->collection->status & RR_HAS_PREIMAGE);
+	int variant = id->variant;
+
+	if (variant < 0)
+		return 0;
+	return (id->collection->status[variant] & RR_HAS_PREIMAGE);
 }
 
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
 	id->collection = find_rerere_dir(hex);
+	id->variant = -1; /* not known yet */
 	return id;
 }
 
@@ -157,16 +217,26 @@ static void read_rr(struct string_list *rr)
 		char *path;
 		unsigned char sha1[20];
 		struct rerere_id *id;
+		int variant;
 
 		/* There has to be the hash, tab, path and then NUL */
 		if (buf.len < 42 || get_sha1_hex(buf.buf, sha1))
 			die("corrupt MERGE_RR");
 
-		if (buf.buf[40] != '\t')
+		if (buf.buf[40] != '.') {
+			variant = 0;
+			path = buf.buf + 40;
+		} else {
+			errno = 0;
+			variant = strtol(buf.buf + 41, &path, 10);
+			if (errno)
+				die("corrupt MERGE_RR");
+		}
+		if (*(path++) != '\t')
 			die("corrupt MERGE_RR");
 		buf.buf[40] = '\0';
-		path = buf.buf + 41;
 		id = new_rerere_id_hex(buf.buf);
+		id->variant = variant;
 		string_list_insert(rr, path)->util = id;
 	}
 	strbuf_release(&buf);
@@ -187,9 +257,16 @@ static int write_rr(struct string_list *rr, int out_fd)
 		id = rr->items[i].util;
 		if (!id)
 			continue;
-		strbuf_addf(&buf, "%s\t%s%c",
-			    rerere_id_hex(id),
-			    rr->items[i].string, 0);
+		assert(id->variant >= 0);
+		if (0 < id->variant)
+			strbuf_addf(&buf, "%s.%d\t%s%c",
+				    rerere_id_hex(id), id->variant,
+				    rr->items[i].string, 0);
+		else
+			strbuf_addf(&buf, "%s\t%s%c",
+				    rerere_id_hex(id),
+				    rr->items[i].string, 0);
+
 		if (write_in_full(out_fd, buf.buf, buf.len) != buf.len)
 			die("unable to write rerere record");
 
@@ -752,7 +829,12 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 			       struct string_list *update)
 {
 	const char *path = rr_item->string;
-	const struct rerere_id *id = rr_item->util;
+	struct rerere_id *id = rr_item->util;
+	int variant;
+
+	if (id->variant < 0)
+		assign_variant(id);
+	variant = id->variant;
 
 	if (!has_rerere_preimage(id)) {
 		/*
@@ -761,13 +843,13 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 		 * the "preimage" file.
 		 */
 		handle_file(path, NULL, rerere_path(id, "preimage"));
-		if (id->collection->status & RR_HAS_POSTIMAGE) {
+		if (id->collection->status[variant] & RR_HAS_POSTIMAGE) {
 			const char *path = rerere_path(id, "postimage");
 			if (unlink(path))
 				die_errno("cannot unlink stray '%s'", path);
-			id->collection->status &= ~RR_HAS_PREIMAGE;
+			id->collection->status[variant] &= ~RR_HAS_PREIMAGE;
 		}
-		id->collection->status |= RR_HAS_PREIMAGE;
+		id->collection->status[variant] |= RR_HAS_PREIMAGE;
 		fprintf(stderr, "Recorded preimage for '%s'\n", path);
 		return;
 	} else if (has_rerere_resolution(id)) {
@@ -784,7 +866,7 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 	} else if (!handle_file(path, NULL, NULL)) {
 		/* The user has resolved it. */
 		copy_file(rerere_path(id, "postimage"), path, 0666);
-		id->collection->status |= RR_HAS_POSTIMAGE;
+		id->collection->status[variant] |= RR_HAS_POSTIMAGE;
 		fprintf(stderr, "Recorded resolution for '%s'.\n", path);
 	} else {
 		return;
@@ -919,6 +1001,7 @@ static int rerere_forget_one_path(const char *path, struct string_list *rr)
 
 	/* Nuke the recorded resolution for the conflict */
 	id = new_rerere_id(sha1);
+	id->variant = 0; /* for now */
 	filename = rerere_path(id, "postimage");
 	if (unlink(filename))
 		return (errno == ENOENT
diff --git a/rerere.h b/rerere.h
index faf5a23..64d38d9 100644
--- a/rerere.h
+++ b/rerere.h
@@ -18,6 +18,7 @@ extern void *RERERE_RESOLVED;
 struct rerere_dir;
 struct rerere_id {
 	struct rerere_dir *collection;
+	int variant;
 };
 
 extern int setup_rerere(struct string_list *, int);

diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index 52a8e09..8d52854 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -407,4 +407,78 @@ test_expect_success 'rerere -h' '
 	test_i18ngrep [Uu]sage help
 '
 
+concat_insert () {
+	last=$1
+	shift
+	cat early && printf "%s\n" "$@" && cat late "$last"
+}
+
+test_expect_failure 'multiple identical conflicts' '
+	git reset --hard &&
+
+	test_seq 1 6 >early &&
+	>late &&
+	test_seq 11 15 >short &&
+	test_seq 111 120 >long &&
+	concat_insert short >file1 &&
+	concat_insert long >file2 &&
+	git add file1 file2 &&
+	git commit -m base &&
+	git tag base &&
+	git checkout -b six.1 &&
+	concat_insert short 6.1 >file1 &&
+	concat_insert long 6.1 >file2 &&
+	git add file1 file2 &&
+	git commit -m 6.1 &&
+	git checkout -b six.2 HEAD^ &&
+	concat_insert short 6.2 >file1 &&
+	concat_insert long 6.2 >file2 &&
+	git add file1 file2 &&
+	git commit -m 6.2 &&
+
+	# At this point, six.1 and six.2
+	# - derive from common ancestor that has two files
+	#   1...6 7 11..15 (file1) and 1...6 7 111..120 (file2)
+	# - six.1 replaces these 7s with 6.1
+	# - six.2 replaces these 7s with 6.2
+
+	test_must_fail git merge six.1 &&
+
+	# Check that rerere knows that file1 and file2 have conflicts
+
+	printf "%s\n" file1 file2 >expect &&
+	git ls-files -u | sed -e "s/^.*	//" | sort -u >actual &&
+	test_cmp expect actual &&
+
+	git rerere status | sort >actual &&
+	test_cmp expect actual &&
+
+	# Resolution is to replace 7 with 6.1 and 6.2 (i.e. take both)
+	concat_insert short 6.1 6.2 >file1 &&
+	concat_insert long 6.1 6.2 >file2 &&
+
+	git rerere remaining >actual &&
+	test_cmp expect actual &&
+
+	# We resolved file1 and file2
+	git rerere &&
+	>expect &&
+	git rerere remaining >actual &&
+	test_cmp expect actual &&
+
+	# Now we should be able to resolve them both
+	git reset --hard &&
+	test_must_fail git merge six.1 &&
+	git rerere &&
+
+	>expect &&
+	git rerere remaining >actual &&
+	test_cmp expect actual &&
+
+	concat_insert short 6.1 6.2 >file1.expect &&
+	concat_insert long 6.1 6.2 >file2.expect &&
+	test_cmp file1.expect file1 &&
+	test_cmp file2.expect file2
+'
+
 test_done

rerere.c, t/t4200-rerere.sh

diff --git a/rerere.c b/rerere.c
index f674461..cefc865 100644
--- a/rerere.c
+++ b/rerere.c
@@ -74,7 +74,9 @@ static void assign_variant(struct rerere_id *id)
 
 	variant = id->variant;
 	if (variant < 0) {
-		variant = 0; /* for now */
+		for (variant = 0; variant < rr_dir->status_nr; variant++)
+			if (!rr_dir->status[variant])
+				break;
 	}
 	fit_variant(rr_dir, variant);
 	id->variant = variant;
@@ -177,15 +179,6 @@ static int has_rerere_resolution(const struct rerere_id *id)
 	return ((id->collection->status[variant] & both) == both);
 }
 
-static int has_rerere_preimage(const struct rerere_id *id)
-{
-	int variant = id->variant;
-
-	if (variant < 0)
-		return 0;
-	return (id->collection->status[variant] & RR_HAS_PREIMAGE);
-}
-
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
@@ -818,6 +811,13 @@ static void update_paths(struct string_list *update)
 		rollback_lock_file(&index_lock);
 }
 
+static void remove_variant(struct rerere_id *id)
+{
+	unlink_or_warn(rerere_path(id, "postimage"));
+	unlink_or_warn(rerere_path(id, "preimage"));
+	id->collection->status[id->variant] = 0;
+}
+
 /*
  * The path indicated by rr_item may still have conflict for which we
  * have a recorded resolution, in which case replay it and optionally
@@ -830,32 +830,42 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 {
 	const char *path = rr_item->string;
 	struct rerere_id *id = rr_item->util;
+	struct rerere_dir *rr_dir = id->collection;
 	int variant;
 
-	if (id->variant < 0)
-		assign_variant(id);
 	variant = id->variant;
 
-	if (!has_rerere_preimage(id)) {
+	/* Has the user resolved it already? */
+	if (variant >= 0) {
+		if (!handle_file(path, NULL, NULL)) {
+			copy_file(rerere_path(id, "postimage"), path, 0666);
+			id->collection->status[variant] |= RR_HAS_POSTIMAGE;
+			fprintf(stderr, "Recorded resolution for '%s'.\n", path);
+			free_rerere_id(rr_item);
+			rr_item->util = NULL;
+			return;
+		}
 		/*
-		 * We are the first to encounter this conflict.  Ask
-		 * handle_file() to write the normalized contents to
-		 * the "preimage" file.
+		 * There may be other variants that can cleanly
+		 * replay.  Try them and update the variant number for
+		 * this one.
 		 */
-		handle_file(path, NULL, rerere_path(id, "preimage"));
-		if (id->collection->status[variant] & RR_HAS_POSTIMAGE) {
-			const char *path = rerere_path(id, "postimage");
-			if (unlink(path))
-				die_errno("cannot unlink stray '%s'", path);
-			id->collection->status[variant] &= ~RR_HAS_PREIMAGE;
-		}
-		id->collection->status[variant] |= RR_HAS_PREIMAGE;
-		fprintf(stderr, "Recorded preimage for '%s'\n", path);
-		return;
-	} else if (has_rerere_resolution(id)) {
-		/* Is there a recorded resolution we could attempt to apply? */
-		if (merge(id, path))
-			return; /* failed to replay */
+	}
+
+	/* Does any existing resolution apply cleanly? */
+	for (variant = 0; variant < rr_dir->status_nr; variant++) {
+		const int both = RR_HAS_PREIMAGE | RR_HAS_POSTIMAGE;
+		struct rerere_id vid = *id;
+
+		if ((rr_dir->status[variant] & both) != both)
+			continue;
+
+		vid.variant = variant;
+		if (merge(&vid, path))
+			continue; /* failed to replay */
+
+		if (0 <= id->variant && id->variant != variant)
+			remove_variant(id);
 
 		if (rerere_autoupdate)
 			string_list_insert(update, path);
@@ -863,16 +873,24 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 			fprintf(stderr,
 				"Resolved '%s' using previous resolution.\n",
 				path);
-	} else if (!handle_file(path, NULL, NULL)) {
-		/* The user has resolved it. */
-		copy_file(rerere_path(id, "postimage"), path, 0666);
-		id->collection->status[variant] |= RR_HAS_POSTIMAGE;
-		fprintf(stderr, "Recorded resolution for '%s'.\n", path);
-	} else {
+		free_rerere_id(rr_item);
+		rr_item->util = NULL;
 		return;
 	}
-	free_rerere_id(rr_item);
-	rr_item->util = NULL;
+
+	/* None of the existing one applies; we need a new variant */
+	assign_variant(id);
+
+	variant = id->variant;
+	handle_file(path, NULL, rerere_path(id, "preimage"));
+	if (id->collection->status[variant] & RR_HAS_POSTIMAGE) {
+		const char *path = rerere_path(id, "postimage");
+		if (unlink(path))
+			die_errno("cannot unlink stray '%s'", path);
+		id->collection->status[variant] &= ~RR_HAS_PREIMAGE;
+	}
+	id->collection->status[variant] |= RR_HAS_PREIMAGE;
+	fprintf(stderr, "Recorded preimage for '%s'\n", path);
 }
 
 static int do_plain_rerere(struct string_list *rr, int fd)
diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index 8d52854..5649829 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -413,7 +413,7 @@ concat_insert () {
 	cat early && printf "%s\n" "$@" && cat late "$last"
 }
 
-test_expect_failure 'multiple identical conflicts' '
+test_expect_success 'multiple identical conflicts' '
 	git reset --hard &&
 
 	test_seq 1 6 >early &&

rerere.c, rerere.h

diff --git a/rerere.c b/rerere.c
index 3d0fa8f..a5d8a06 100644
--- a/rerere.c
+++ b/rerere.c
@@ -8,6 +8,7 @@
 #include "ll-merge.h"
 #include "attr.h"
 #include "pathspec.h"
+#include "sha1-lookup.h"
 
 #define RESOLVED 0
 #define PUNTED 1
@@ -22,6 +23,23 @@ static int rerere_autoupdate;
 
 static char *merge_rr_path;
 
+static int rerere_dir_nr;
+static int rerere_dir_alloc;
+
+static struct rerere_dir {
+	unsigned char sha1[20];
+} **rerere_dir;
+
+static void free_rerere_dirs(void)
+{
+	int i;
+	for (i = 0; i < rerere_dir_nr; i++)
+		free(rerere_dir[i]);
+	free(rerere_dir);
+	rerere_dir_nr = rerere_dir_alloc = 0;
+	rerere_dir = NULL;
+}
+
 static void free_rerere_id(struct string_list_item *item)
 {
 	free(item->util);
@@ -29,7 +47,7 @@ static void free_rerere_id(struct string_list_item *item)
 
 static const char *rerere_id_hex(const struct rerere_id *id)
 {
-	return id->hex;
+	return sha1_to_hex(id->collection->sha1);
 }
 
 const char *rerere_path(const struct rerere_id *id, const char *file)
@@ -40,6 +58,37 @@ const char *rerere_path(const struct rerere_id *id, const char *file)
 	return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
 }
 
+static const unsigned char *rerere_dir_sha1(size_t i, void *table)
+{
+	struct rerere_dir **rr_dir = table;
+	return rr_dir[i]->sha1;
+}
+
+static struct rerere_dir *find_rerere_dir(const char *hex)
+{
+	unsigned char sha1[20];
+	struct rerere_dir *rr_dir;
+	int pos;
+
+	if (get_sha1_hex(hex, sha1))
+		return NULL; /* BUG */
+	pos = sha1_pos(sha1, rerere_dir, rerere_dir_nr, rerere_dir_sha1);
+	if (pos < 0) {
+		rr_dir = xmalloc(sizeof(*rr_dir));
+		hashcpy(rr_dir->sha1, sha1);
+		pos = -1 - pos;
+
+		/* Make sure the array is big enough ... */
+		ALLOC_GROW(rerere_dir, rerere_dir_nr + 1, rerere_dir_alloc);
+		/* ... and add it in. */
+		rerere_dir_nr++;
+		memmove(rerere_dir + pos + 1, rerere_dir + pos,
+			(rerere_dir_nr - pos - 1) * sizeof(*rerere_dir));
+		rerere_dir[pos] = rr_dir;
+	}
+	return rerere_dir[pos];
+}
+
 static int has_rerere_resolution(const struct rerere_id *id)
 {
 	struct stat st;
@@ -50,7 +99,7 @@ static int has_rerere_resolution(const struct rerere_id *id)
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
-	xsnprintf(id->hex, sizeof(id->hex), "%s", hex);
+	id->collection = find_rerere_dir(hex);
 	return id;
 }
 
@@ -810,12 +859,14 @@ int setup_rerere(struct string_list *merge_rr, int flags)
 int rerere(int flags)
 {
 	struct string_list merge_rr = STRING_LIST_INIT_DUP;
-	int fd;
+	int fd, status;
 
 	fd = setup_rerere(&merge_rr, flags);
 	if (fd < 0)
 		return 0;
-	return do_plain_rerere(&merge_rr, fd);
+	status = do_plain_rerere(&merge_rr, fd);
+	free_rerere_dirs();
+	return status;
 }
 
 static int rerere_forget_one_path(const char *path, struct string_list *rr)
@@ -900,7 +951,7 @@ int rerere_forget(struct pathspec *pathspec)
 static struct rerere_id *dirname_to_id(const char *name)
 {
 	static struct rerere_id id;
-	xsnprintf(id.hex, sizeof(id.hex), "%s", name);
+	id.collection = find_rerere_dir(name);
 	return &id;
 }
 
diff --git a/rerere.h b/rerere.h
index ce545d0..faf5a23 100644
--- a/rerere.h
+++ b/rerere.h
@@ -15,8 +15,9 @@ struct pathspec;
  */
 extern void *RERERE_RESOLVED;
 
+struct rerere_dir;
 struct rerere_id {
-	char hex[41];
+	struct rerere_dir *collection;
 };
 
 extern int setup_rerere(struct string_list *, int);

diff --git a/rerere.c b/rerere.c
index a5d8a06..fbdade8 100644
--- a/rerere.c
+++ b/rerere.c
@@ -26,8 +26,11 @@ static char *merge_rr_path;
 static int rerere_dir_nr;
 static int rerere_dir_alloc;
 
+#define RR_HAS_POSTIMAGE 1
+#define RR_HAS_PREIMAGE 2
 static struct rerere_dir {
 	unsigned char sha1[20];
+	unsigned char status;
 } **rerere_dir;
 
 static void free_rerere_dirs(void)
@@ -58,6 +61,27 @@ const char *rerere_path(const struct rerere_id *id, const char *file)
 	return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
 }
 
+static int is_rr_file(const char *name, const char *filename)
+{
+	return !strcmp(name, filename);
+}
+
+static void scan_rerere_dir(struct rerere_dir *rr_dir)
+{
+	struct dirent *de;
+	DIR *dir = opendir(git_path("rr-cache/%s", sha1_to_hex(rr_dir->sha1)));
+
+	if (!dir)
+		return;
+	while ((de = readdir(dir)) != NULL) {
+		if (is_rr_file(de->d_name, "postimage"))
+			rr_dir->status |= RR_HAS_POSTIMAGE;
+		else if (is_rr_file(de->d_name, "preimage"))
+			rr_dir->status |= RR_HAS_PREIMAGE;
+	}
+	closedir(dir);
+}
+
 static const unsigned char *rerere_dir_sha1(size_t i, void *table)
 {
 	struct rerere_dir **rr_dir = table;
@@ -76,6 +100,7 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 	if (pos < 0) {
 		rr_dir = xmalloc(sizeof(*rr_dir));
 		hashcpy(rr_dir->sha1, sha1);
+		rr_dir->status = 0;
 		pos = -1 - pos;
 
 		/* Make sure the array is big enough ... */
@@ -85,15 +110,14 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 		memmove(rerere_dir + pos + 1, rerere_dir + pos,
 			(rerere_dir_nr - pos - 1) * sizeof(*rerere_dir));
 		rerere_dir[pos] = rr_dir;
+		scan_rerere_dir(rr_dir);
 	}
 	return rerere_dir[pos];
 }
 
 static int has_rerere_resolution(const struct rerere_id *id)
 {
-	struct stat st;
-
-	return !stat(rerere_path(id, "postimage"), &st);
+	return (id->collection->status & RR_HAS_POSTIMAGE);
 }
 
 static struct rerere_id *new_rerere_id_hex(char *hex)
@@ -737,6 +761,7 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 	} else if (!handle_file(path, NULL, NULL)) {
 		/* The user has resolved it. */
 		copy_file(rerere_path(id, "postimage"), path, 0666);
+		id->collection->status |= RR_HAS_POSTIMAGE;
 		fprintf(stderr, "Recorded resolution for '%s'.\n", path);
 	} else {
 		return;
@@ -797,6 +822,7 @@ static int do_plain_rerere(struct string_list *rr, int fd)
 		 * normalized contents to the "preimage" file.
 		 */
 		handle_file(path, NULL, rerere_path(id, "preimage"));
+		id->collection->status |= RR_HAS_PREIMAGE;
 		fprintf(stderr, "Recorded preimage for '%s'\n", path);
 	}
 

rerere.c, t/t4200-rerere.sh

diff --git a/rerere.c b/rerere.c
index fbdade8..a1e2963 100644
--- a/rerere.c
+++ b/rerere.c
@@ -117,7 +117,9 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 
 static int has_rerere_resolution(const struct rerere_id *id)
 {
-	return (id->collection->status & RR_HAS_POSTIMAGE);
+	const int both = RR_HAS_POSTIMAGE|RR_HAS_PREIMAGE;
+
+	return ((id->collection->status & both) == both);
 }
 
 static struct rerere_id *new_rerere_id_hex(char *hex)
@@ -806,24 +808,30 @@ static int do_plain_rerere(struct string_list *rr, int fd)
 		string_list_insert(rr, path)->util = id;
 
 		/*
-		 * If the directory does not exist, create
-		 * it.  mkdir_in_gitdir() will fail with
-		 * EEXIST if there already is one.
-		 *
-		 * NEEDSWORK: make sure "gc" does not remove
-		 * preimage without removing the directory.
+		 * Ensure that the directory exists.
+		 * mkdir_in_gitdir() will fail with EEXIST if there
+		 * already is one.
 		 */
-		if (mkdir_in_gitdir(rerere_path(id, NULL)))
-			continue;
+		if (mkdir_in_gitdir(rerere_path(id, NULL)) &&
+		    errno != EEXIST)
+			continue; /* NEEDSWORK: perhaps we should die? */
 
-		/*
-		 * We are the first to encounter this
-		 * conflict.  Ask handle_file() to write the
-		 * normalized contents to the "preimage" file.
-		 */
-		handle_file(path, NULL, rerere_path(id, "preimage"));
-		id->collection->status |= RR_HAS_PREIMAGE;
-		fprintf(stderr, "Recorded preimage for '%s'\n", path);
+		if (id->collection->status & RR_HAS_PREIMAGE) {
+			;
+		} else {
+			/*
+			 * We are the first to encounter this
+			 * conflict.  Ask handle_file() to write the
+			 * normalized contents to the "preimage" file.
+			 *
+			 * NEEDSWORK: what should happen if we had a
+			 * leftover postimage that is totally
+			 * unrelated?  Perhaps we should unlink it?
+			 */
+			handle_file(path, NULL, rerere_path(id, "preimage"));
+			id->collection->status |= RR_HAS_PREIMAGE;
+			fprintf(stderr, "Recorded preimage for '%s'\n", path);
+		}
 	}
 
 	for (i = 0; i < rr->nr; i++)
diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index ed9c91e..c428011 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -184,12 +184,27 @@ test_expect_success 'rerere updates postimage timestamp' '
 '
 
 test_expect_success 'rerere clear' '
-	rm $rr/postimage &&
+	mv $rr/postimage .git/post-saved &&
 	echo "$sha1	a1" | perl -pe "y/\012/\000/" >.git/MERGE_RR &&
 	git rerere clear &&
 	! test -d $rr
 '
 
+test_expect_success 'leftover directory' '
+	git reset --hard &&
+	mkdir -p $rr &&
+	test_must_fail git merge first &&
+	test -f $rr/preimage
+'
+
+test_expect_success 'missing preimage' '
+	git reset --hard &&
+	mkdir -p $rr &&
+	cp .git/post-saved $rr/postimage &&
+	test_must_fail git merge first &&
+	test -f $rr/preimage
+'
+
 test_expect_success 'set up for garbage collection tests' '
 	mkdir -p $rr &&
 	echo Hello >$rr/preimage &&

diff --git a/rerere.c b/rerere.c
index a1e2963..33b1348 100644
--- a/rerere.c
+++ b/rerere.c
@@ -122,6 +122,11 @@ static int has_rerere_resolution(const struct rerere_id *id)
 	return ((id->collection->status & both) == both);
 }
 
+static int has_rerere_preimage(const struct rerere_id *id)
+{
+	return (id->collection->status & RR_HAS_PREIMAGE);
+}
+
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
@@ -749,8 +754,24 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 	const char *path = rr_item->string;
 	const struct rerere_id *id = rr_item->util;
 
-	/* Is there a recorded resolution we could attempt to apply? */
-	if (has_rerere_resolution(id)) {
+	if (!has_rerere_preimage(id)) {
+		/*
+		 * We are the first to encounter this conflict.  Ask
+		 * handle_file() to write the normalized contents to
+		 * the "preimage" file.
+		 */
+		handle_file(path, NULL, rerere_path(id, "preimage"));
+		if (id->collection->status & RR_HAS_POSTIMAGE) {
+			const char *path = rerere_path(id, "postimage");
+			if (unlink(path))
+				die_errno("cannot unlink stray '%s'", path);
+			id->collection->status &= ~RR_HAS_POSTIMAGE;
+		}
+		id->collection->status |= RR_HAS_PREIMAGE;
+		fprintf(stderr, "Recorded preimage for '%s'\n", path);
+		return;
+	} else if (has_rerere_resolution(id)) {
+		/* Is there a recorded resolution we could attempt to apply? */
 		if (merge(id, path))
 			return; /* failed to replay */
 
@@ -807,31 +828,8 @@ static int do_plain_rerere(struct string_list *rr, int fd)
 		id = new_rerere_id(sha1);
 		string_list_insert(rr, path)->util = id;
 
-		/*
-		 * Ensure that the directory exists.
-		 * mkdir_in_gitdir() will fail with EEXIST if there
-		 * already is one.
-		 */
-		if (mkdir_in_gitdir(rerere_path(id, NULL)) &&
-		    errno != EEXIST)
-			continue; /* NEEDSWORK: perhaps we should die? */
-
-		if (id->collection->status & RR_HAS_PREIMAGE) {
-			;
-		} else {
-			/*
-			 * We are the first to encounter this
-			 * conflict.  Ask handle_file() to write the
-			 * normalized contents to the "preimage" file.
-			 *
-			 * NEEDSWORK: what should happen if we had a
-			 * leftover postimage that is totally
-			 * unrelated?  Perhaps we should unlink it?
-			 */
-			handle_file(path, NULL, rerere_path(id, "preimage"));
-			id->collection->status |= RR_HAS_PREIMAGE;
-			fprintf(stderr, "Recorded preimage for '%s'\n", path);
-		}
+		/* Ensure that the directory exists. */
+		mkdir_in_gitdir(rerere_path(id, NULL));
 	}
 
 	for (i = 0; i < rr->nr; i++)

rerere.c, rerere.h

diff --git a/rerere.c b/rerere.c
index 33b1348..0cf857b 100644
--- a/rerere.c
+++ b/rerere.c
@@ -30,14 +30,17 @@ static int rerere_dir_alloc;
 #define RR_HAS_PREIMAGE 2
 static struct rerere_dir {
 	unsigned char sha1[20];
-	unsigned char status;
+	int status_alloc, status_nr;
+	unsigned char *status;
 } **rerere_dir;
 
 static void free_rerere_dirs(void)
 {
 	int i;
-	for (i = 0; i < rerere_dir_nr; i++)
+	for (i = 0; i < rerere_dir_nr; i++) {
+		free(rerere_dir[i]->status);
 		free(rerere_dir[i]);
+	}
 	free(rerere_dir);
 	rerere_dir_nr = rerere_dir_alloc = 0;
 	rerere_dir = NULL;
@@ -53,17 +56,59 @@ static const char *rerere_id_hex(const struct rerere_id *id)
 	return sha1_to_hex(id->collection->sha1);
 }
 
+static void fit_variant(struct rerere_dir *rr_dir, int variant)
+{
+	variant++;
+	ALLOC_GROW(rr_dir->status, variant, rr_dir->status_alloc);
+	if (rr_dir->status_nr < variant) {
+		memset(rr_dir->status + rr_dir->status_nr,
+		       '\0', variant - rr_dir->status_nr);
+		rr_dir->status_nr = variant;
+	}
+}
+
+static void assign_variant(struct rerere_id *id)
+{
+	int variant;
+	struct rerere_dir *rr_dir = id->collection;
+
+	variant = id->variant;
+	if (variant < 0) {
+		variant = 0; /* for now */
+	}
+	fit_variant(rr_dir, variant);
+	id->variant = variant;
+}
+
 const char *rerere_path(const struct rerere_id *id, const char *file)
 {
 	if (!file)
 		return git_path("rr-cache/%s", rerere_id_hex(id));
 
-	return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
+	if (id->variant <= 0)
+		return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
+
+	return git_path("rr-cache/%s/%s.%d",
+			rerere_id_hex(id), file, id->variant);
 }
 
-static int is_rr_file(const char *name, const char *filename)
+static int is_rr_file(const char *name, const char *filename, int *variant)
 {
-	return !strcmp(name, filename);
+	const char *suffix;
+	char *ep;
+
+	if (!strcmp(name, filename)) {
+		*variant = 0;
+		return 1;
+	}
+	if (!skip_prefix(name, filename, &suffix) || *suffix != '.')
+		return 0;
+
+	errno = 0;
+	*variant = strtol(suffix + 1, &ep, 10);
+	if (errno || *ep)
+		return 0;
+	return 1;
 }
 
 static void scan_rerere_dir(struct rerere_dir *rr_dir)
@@ -74,10 +119,15 @@ static void scan_rerere_dir(struct rerere_dir *rr_dir)
 	if (!dir)
 		return;
 	while ((de = readdir(dir)) != NULL) {
-		if (is_rr_file(de->d_name, "postimage"))
-			rr_dir->status |= RR_HAS_POSTIMAGE;
-		else if (is_rr_file(de->d_name, "preimage"))
-			rr_dir->status |= RR_HAS_PREIMAGE;
+		int variant;
+
+		if (is_rr_file(de->d_name, "postimage", &variant)) {
+			fit_variant(rr_dir, variant);
+			rr_dir->status[variant] |= RR_HAS_POSTIMAGE;
+		} else if (is_rr_file(de->d_name, "preimage", &variant)) {
+			fit_variant(rr_dir, variant);
+			rr_dir->status[variant] |= RR_HAS_PREIMAGE;
+		}
 	}
 	closedir(dir);
 }
@@ -100,7 +150,9 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 	if (pos < 0) {
 		rr_dir = xmalloc(sizeof(*rr_dir));
 		hashcpy(rr_dir->sha1, sha1);
-		rr_dir->status = 0;
+		rr_dir->status = NULL;
+		rr_dir->status_nr = 0;
+		rr_dir->status_alloc = 0;
 		pos = -1 - pos;
 
 		/* Make sure the array is big enough ... */
@@ -118,19 +170,27 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 static int has_rerere_resolution(const struct rerere_id *id)
 {
 	const int both = RR_HAS_POSTIMAGE|RR_HAS_PREIMAGE;
+	int variant = id->variant;
 
-	return ((id->collection->status & both) == both);
+	if (variant < 0)
+		return 0;
+	return ((id->collection->status[variant] & both) == both);
 }
 
 static int has_rerere_preimage(const struct rerere_id *id)
 {
-	return (id->collection->status & RR_HAS_PREIMAGE);
+	int variant = id->variant;
+
+	if (variant < 0)
+		return 0;
+	return (id->collection->status[variant] & RR_HAS_PREIMAGE);
 }
 
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
 	id->collection = find_rerere_dir(hex);
+	id->variant = -1; /* not known yet */
 	return id;
 }
 
@@ -157,16 +217,26 @@ static void read_rr(struct string_list *rr)
 		char *path;
 		unsigned char sha1[20];
 		struct rerere_id *id;
+		int variant;
 
 		/* There has to be the hash, tab, path and then NUL */
 		if (buf.len < 42 || get_sha1_hex(buf.buf, sha1))
 			die("corrupt MERGE_RR");
 
-		if (buf.buf[40] != '\t')
+		if (buf.buf[40] != '.') {
+			variant = 0;
+			path = buf.buf + 40;
+		} else {
+			errno = 0;
+			variant = strtol(buf.buf + 41, &path, 10);
+			if (errno)
+				die("corrupt MERGE_RR");
+		}
+		if (*(path++) != '\t')
 			die("corrupt MERGE_RR");
 		buf.buf[40] = '\0';
-		path = buf.buf + 41;
 		id = new_rerere_id_hex(buf.buf);
+		id->variant = variant;
 		string_list_insert(rr, path)->util = id;
 	}
 	strbuf_release(&buf);
@@ -187,9 +257,16 @@ static int write_rr(struct string_list *rr, int out_fd)
 		id = rr->items[i].util;
 		if (!id)
 			continue;
-		strbuf_addf(&buf, "%s\t%s%c",
-			    rerere_id_hex(id),
-			    rr->items[i].string, 0);
+		assert(id->variant >= 0);
+		if (0 < id->variant)
+			strbuf_addf(&buf, "%s.%d\t%s%c",
+				    rerere_id_hex(id), id->variant,
+				    rr->items[i].string, 0);
+		else
+			strbuf_addf(&buf, "%s\t%s%c",
+				    rerere_id_hex(id),
+				    rr->items[i].string, 0);
+
 		if (write_in_full(out_fd, buf.buf, buf.len) != buf.len)
 			die("unable to write rerere record");
 
@@ -752,7 +829,12 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 			       struct string_list *update)
 {
 	const char *path = rr_item->string;
-	const struct rerere_id *id = rr_item->util;
+	struct rerere_id *id = rr_item->util;
+	int variant;
+
+	if (id->variant < 0)
+		assign_variant(id);
+	variant = id->variant;
 
 	if (!has_rerere_preimage(id)) {
 		/*
@@ -761,13 +843,13 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 		 * the "preimage" file.
 		 */
 		handle_file(path, NULL, rerere_path(id, "preimage"));
-		if (id->collection->status & RR_HAS_POSTIMAGE) {
+		if (id->collection->status[variant] & RR_HAS_POSTIMAGE) {
 			const char *path = rerere_path(id, "postimage");
 			if (unlink(path))
 				die_errno("cannot unlink stray '%s'", path);
-			id->collection->status &= ~RR_HAS_POSTIMAGE;
+			id->collection->status[variant] &= ~RR_HAS_POSTIMAGE;
 		}
-		id->collection->status |= RR_HAS_PREIMAGE;
+		id->collection->status[variant] |= RR_HAS_PREIMAGE;
 		fprintf(stderr, "Recorded preimage for '%s'\n", path);
 		return;
 	} else if (has_rerere_resolution(id)) {
@@ -784,7 +866,7 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 	} else if (!handle_file(path, NULL, NULL)) {
 		/* The user has resolved it. */
 		copy_file(rerere_path(id, "postimage"), path, 0666);
-		id->collection->status |= RR_HAS_POSTIMAGE;
+		id->collection->status[variant] |= RR_HAS_POSTIMAGE;
 		fprintf(stderr, "Recorded resolution for '%s'.\n", path);
 	} else {
 		return;
@@ -919,6 +1001,7 @@ static int rerere_forget_one_path(const char *path, struct string_list *rr)
 
 	/* Nuke the recorded resolution for the conflict */
 	id = new_rerere_id(sha1);
+	id->variant = 0; /* for now */
 	filename = rerere_path(id, "postimage");
 	if (unlink(filename))
 		return (errno == ENOENT
diff --git a/rerere.h b/rerere.h
index faf5a23..64d38d9 100644
--- a/rerere.h
+++ b/rerere.h
@@ -18,6 +18,7 @@ extern void *RERERE_RESOLVED;
 struct rerere_dir;
 struct rerere_id {
 	struct rerere_dir *collection;
+	int variant;
 };
 
 extern int setup_rerere(struct string_list *, int);

diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index c428011..6fcc6d4 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -406,4 +406,78 @@ test_expect_success 'rerere -h' '
 	test_i18ngrep [Uu]sage help
 '
 
+concat_insert () {
+	last=$1
+	shift
+	cat early && printf "%s\n" "$@" && cat late "$last"
+}
+
+test_expect_failure 'multiple identical conflicts' '
+	git reset --hard &&
+
+	test_seq 1 6 >early &&
+	>late &&
+	test_seq 11 15 >short &&
+	test_seq 111 120 >long &&
+	concat_insert short >file1 &&
+	concat_insert long >file2 &&
+	git add file1 file2 &&
+	git commit -m base &&
+	git tag base &&
+	git checkout -b six.1 &&
+	concat_insert short 6.1 >file1 &&
+	concat_insert long 6.1 >file2 &&
+	git add file1 file2 &&
+	git commit -m 6.1 &&
+	git checkout -b six.2 HEAD^ &&
+	concat_insert short 6.2 >file1 &&
+	concat_insert long 6.2 >file2 &&
+	git add file1 file2 &&
+	git commit -m 6.2 &&
+
+	# At this point, six.1 and six.2
+	# - derive from common ancestor that has two files
+	#   1...6 7 11..15 (file1) and 1...6 7 111..120 (file2)
+	# - six.1 replaces these 7s with 6.1
+	# - six.2 replaces these 7s with 6.2
+
+	test_must_fail git merge six.1 &&
+
+	# Check that rerere knows that file1 and file2 have conflicts
+
+	printf "%s\n" file1 file2 >expect &&
+	git ls-files -u | sed -e "s/^.*	//" | sort -u >actual &&
+	test_cmp expect actual &&
+
+	git rerere status | sort >actual &&
+	test_cmp expect actual &&
+
+	# Resolution is to replace 7 with 6.1 and 6.2 (i.e. take both)
+	concat_insert short 6.1 6.2 >file1 &&
+	concat_insert long 6.1 6.2 >file2 &&
+
+	git rerere remaining >actual &&
+	test_cmp expect actual &&
+
+	# We resolved file1 and file2
+	git rerere &&
+	>expect &&
+	git rerere remaining >actual &&
+	test_cmp expect actual &&
+
+	# Now we should be able to resolve them both
+	git reset --hard &&
+	test_must_fail git merge six.1 &&
+	git rerere &&
+
+	>expect &&
+	git rerere remaining >actual &&
+	test_cmp expect actual &&
+
+	concat_insert short 6.1 6.2 >file1.expect &&
+	concat_insert long 6.1 6.2 >file2.expect &&
+	test_cmp file1.expect file1 &&
+	test_cmp file2.expect file2
+'
+
 test_done

rerere.c, t/t4200-rerere.sh

diff --git a/rerere.c b/rerere.c
index 0cf857b..353227c 100644
--- a/rerere.c
+++ b/rerere.c
@@ -74,7 +74,9 @@ static void assign_variant(struct rerere_id *id)
 
 	variant = id->variant;
 	if (variant < 0) {
-		variant = 0; /* for now */
+		for (variant = 0; variant < rr_dir->status_nr; variant++)
+			if (!rr_dir->status[variant])
+				break;
 	}
 	fit_variant(rr_dir, variant);
 	id->variant = variant;
@@ -177,15 +179,6 @@ static int has_rerere_resolution(const struct rerere_id *id)
 	return ((id->collection->status[variant] & both) == both);
 }
 
-static int has_rerere_preimage(const struct rerere_id *id)
-{
-	int variant = id->variant;
-
-	if (variant < 0)
-		return 0;
-	return (id->collection->status[variant] & RR_HAS_PREIMAGE);
-}
-
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
@@ -818,6 +811,13 @@ static void update_paths(struct string_list *update)
 		rollback_lock_file(&index_lock);
 }
 
+static void remove_variant(struct rerere_id *id)
+{
+	unlink_or_warn(rerere_path(id, "postimage"));
+	unlink_or_warn(rerere_path(id, "preimage"));
+	id->collection->status[id->variant] = 0;
+}
+
 /*
  * The path indicated by rr_item may still have conflict for which we
  * have a recorded resolution, in which case replay it and optionally
@@ -830,32 +830,46 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 {
 	const char *path = rr_item->string;
 	struct rerere_id *id = rr_item->util;
+	struct rerere_dir *rr_dir = id->collection;
 	int variant;
 
-	if (id->variant < 0)
-		assign_variant(id);
 	variant = id->variant;
 
-	if (!has_rerere_preimage(id)) {
+	/* Has the user resolved it already? */
+	if (variant >= 0) {
+		if (!handle_file(path, NULL, NULL)) {
+			copy_file(rerere_path(id, "postimage"), path, 0666);
+			id->collection->status[variant] |= RR_HAS_POSTIMAGE;
+			fprintf(stderr, "Recorded resolution for '%s'.\n", path);
+			free_rerere_id(rr_item);
+			rr_item->util = NULL;
+			return;
+		}
 		/*
-		 * We are the first to encounter this conflict.  Ask
-		 * handle_file() to write the normalized contents to
-		 * the "preimage" file.
+		 * There may be other variants that can cleanly
+		 * replay.  Try them and update the variant number for
+		 * this one.
 		 */
-		handle_file(path, NULL, rerere_path(id, "preimage"));
-		if (id->collection->status[variant] & RR_HAS_POSTIMAGE) {
-			const char *path = rerere_path(id, "postimage");
-			if (unlink(path))
-				die_errno("cannot unlink stray '%s'", path);
-			id->collection->status[variant] &= ~RR_HAS_POSTIMAGE;
-		}
-		id->collection->status[variant] |= RR_HAS_PREIMAGE;
-		fprintf(stderr, "Recorded preimage for '%s'\n", path);
-		return;
-	} else if (has_rerere_resolution(id)) {
-		/* Is there a recorded resolution we could attempt to apply? */
-		if (merge(id, path))
-			return; /* failed to replay */
+	}
+
+	/* Does any existing resolution apply cleanly? */
+	for (variant = 0; variant < rr_dir->status_nr; variant++) {
+		const int both = RR_HAS_PREIMAGE | RR_HAS_POSTIMAGE;
+		struct rerere_id vid = *id;
+
+		if ((rr_dir->status[variant] & both) != both)
+			continue;
+
+		vid.variant = variant;
+		if (merge(&vid, path))
+			continue; /* failed to replay */
+
+		/*
+		 * If there already is a different variant that applies
+		 * cleanly, there is no point maintaining our own variant.
+		 */
+		if (0 <= id->variant && id->variant != variant)
+			remove_variant(id);
 
 		if (rerere_autoupdate)
 			string_list_insert(update, path);
@@ -863,16 +877,24 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 			fprintf(stderr,
 				"Resolved '%s' using previous resolution.\n",
 				path);
-	} else if (!handle_file(path, NULL, NULL)) {
-		/* The user has resolved it. */
-		copy_file(rerere_path(id, "postimage"), path, 0666);
-		id->collection->status[variant] |= RR_HAS_POSTIMAGE;
-		fprintf(stderr, "Recorded resolution for '%s'.\n", path);
-	} else {
+		free_rerere_id(rr_item);
+		rr_item->util = NULL;
 		return;
 	}
-	free_rerere_id(rr_item);
-	rr_item->util = NULL;
+
+	/* None of the existing one applies; we need a new variant */
+	assign_variant(id);
+
+	variant = id->variant;
+	handle_file(path, NULL, rerere_path(id, "preimage"));
+	if (id->collection->status[variant] & RR_HAS_POSTIMAGE) {
+		const char *path = rerere_path(id, "postimage");
+		if (unlink(path))
+			die_errno("cannot unlink stray '%s'", path);
+		id->collection->status[variant] &= ~RR_HAS_POSTIMAGE;
+	}
+	id->collection->status[variant] |= RR_HAS_PREIMAGE;
+	fprintf(stderr, "Recorded preimage for '%s'\n", path);
 }
 
 static int do_plain_rerere(struct string_list *rr, int fd)
diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index 6fcc6d4..b1bda20 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -412,7 +412,7 @@ concat_insert () {
 	cat early && printf "%s\n" "$@" && cat late "$last"
 }
 
-test_expect_failure 'multiple identical conflicts' '
+test_expect_success 'multiple identical conflicts' '
 	git reset --hard &&
 
 	test_seq 1 6 >early &&

rerere.c, t/t4200-rerere.sh

diff --git a/rerere.c b/rerere.c
index 353227c..3d4dd33 100644
--- a/rerere.c
+++ b/rerere.c
@@ -1081,29 +1081,16 @@ int rerere_forget(struct pathspec *pathspec)
  * Garbage collection support
  */
 
-/*
- * Note that this is not reentrant but is used only one-at-a-time
- * so it does not matter right now.
- */
-static struct rerere_id *dirname_to_id(const char *name)
-{
-	static struct rerere_id id;
-	id.collection = find_rerere_dir(name);
-	return &id;
-}
-
-static time_t rerere_created_at(const char *dir_name)
+static time_t rerere_created_at(struct rerere_id *id)
 {
 	struct stat st;
-	struct rerere_id *id = dirname_to_id(dir_name);
 
 	return stat(rerere_path(id, "preimage"), &st) ? (time_t) 0 : st.st_mtime;
 }
 
-static time_t rerere_last_used_at(const char *dir_name)
+static time_t rerere_last_used_at(struct rerere_id *id)
 {
 	struct stat st;
-	struct rerere_id *id = dirname_to_id(dir_name);
 
 	return stat(rerere_path(id, "postimage"), &st) ? (time_t) 0 : st.st_mtime;
 }
@@ -1113,15 +1100,28 @@ static time_t rerere_last_used_at(const char *dir_name)
  */
 static void unlink_rr_item(struct rerere_id *id)
 {
-	unlink(rerere_path(id, "thisimage"));
-	unlink(rerere_path(id, "preimage"));
-	unlink(rerere_path(id, "postimage"));
-	/*
-	 * NEEDSWORK: what if this rmdir() fails?  Wouldn't we then
-	 * assume that we already have preimage recorded in
-	 * do_plain_rerere()?
-	 */
-	rmdir(rerere_path(id, NULL));
+	unlink_or_warn(rerere_path(id, "thisimage"));
+	remove_variant(id);
+	id->collection->status[id->variant] = 0;
+}
+
+static void prune_one(struct rerere_id *id, time_t now,
+		      int cutoff_resolve, int cutoff_noresolve)
+{
+	time_t then;
+	int cutoff;
+
+	then = rerere_last_used_at(id);
+	if (then)
+		cutoff = cutoff_resolve;
+	else {
+		then = rerere_created_at(id);
+		if (!then)
+			return;
+		cutoff = cutoff_noresolve;
+	}
+	if (then < now - cutoff * 86400)
+		unlink_rr_item(id);
 }
 
 void rerere_gc(struct string_list *rr)
@@ -1129,8 +1129,8 @@ void rerere_gc(struct string_list *rr)
 	struct string_list to_remove = STRING_LIST_INIT_DUP;
 	DIR *dir;
 	struct dirent *e;
-	int i, cutoff;
-	time_t now = time(NULL), then;
+	int i;
+	time_t now = time(NULL);
 	int cutoff_noresolve = 15;
 	int cutoff_resolve = 60;
 
@@ -1142,25 +1142,32 @@ void rerere_gc(struct string_list *rr)
 		die_errno("unable to open rr-cache directory");
 	/* Collect stale conflict IDs ... */
 	while ((e = readdir(dir))) {
+		struct rerere_dir *rr_dir;
+		struct rerere_id id;
+		int now_empty;
+
 		if (is_dot_or_dotdot(e->d_name))
 			continue;
-
-		then = rerere_last_used_at(e->d_name);
-		if (then) {
-			cutoff = cutoff_resolve;
-		} else {
-			then = rerere_created_at(e->d_name);
-			if (!then)
-				continue;
-			cutoff = cutoff_noresolve;
+		rr_dir = find_rerere_dir(e->d_name);
+		if (!rr_dir)
+			continue; /* or should we remove e->d_name? */
+
+		now_empty = 1;
+		for (id.variant = 0, id.collection = rr_dir;
+		     id.variant < id.collection->status_nr;
+		     id.variant++) {
+			prune_one(&id, now, cutoff_resolve, cutoff_noresolve);
+			if (id.collection->status[id.variant])
+				now_empty = 0;
 		}
-		if (then < now - cutoff * 86400)
+		if (now_empty)
 			string_list_append(&to_remove, e->d_name);
 	}
 	closedir(dir);
-	/* ... and then remove them one-by-one */
+
+	/* ... and then remove the empty directories */
 	for (i = 0; i < to_remove.nr; i++)
-		unlink_rr_item(dirname_to_id(to_remove.items[i].string));
+		rmdir(git_path("rr-cache/%s", to_remove.items[i].string));
 	string_list_clear(&to_remove, 0);
 }
 
@@ -1177,8 +1184,10 @@ void rerere_clear(struct string_list *merge_rr)
 
 	for (i = 0; i < merge_rr->nr; i++) {
 		struct rerere_id *id = merge_rr->items[i].util;
-		if (!has_rerere_resolution(id))
+		if (!has_rerere_resolution(id)) {
 			unlink_rr_item(id);
+			rmdir(rerere_path(id, NULL));
+		}
 	}
 	unlink_or_warn(git_path("MERGE_RR"));
 }
diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index b1bda20..647ea6f 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -412,6 +412,39 @@ concat_insert () {
 	cat early && printf "%s\n" "$@" && cat late "$last"
 }
 
+count_pre_post () {
+	find .git/rr-cache/ -type f -name "preimage*" >actual &&
+	test_line_count = "$1" actual &&
+	find .git/rr-cache/ -type f -name "postimage*" >actual &&
+	test_line_count = "$2" actual
+}
+
+test_expect_success 'rerere gc' '
+	find .git/rr-cache -type f >original &&
+	xargs test-chmtime -172800 <original &&
+
+	git -c gc.rerereresolved=5 -c gc.rerereunresolved=5 rerere gc &&
+	find .git/rr-cache -type f >actual &&
+	test_cmp original actual &&
+
+	git -c gc.rerereresolved=5 -c gc.rerereunresolved=0 rerere gc &&
+	find .git/rr-cache -type f >actual &&
+	test_cmp original actual &&
+
+	git -c gc.rerereresolved=0 -c gc.rerereunresolved=0 rerere gc &&
+	find .git/rr-cache -type f >actual &&
+	>expect &&
+	test_cmp expect actual
+'
+
+merge_conflict_resolve () {
+	git reset --hard &&
+	test_must_fail git merge six.1 &&
+	# Resolution is to replace 7 with 6.1 and 6.2 (i.e. take both)
+	concat_insert short 6.1 6.2 >file1 &&
+	concat_insert long 6.1 6.2 >file2
+}
+
 test_expect_success 'multiple identical conflicts' '
 	git reset --hard &&
 
@@ -441,10 +474,9 @@ test_expect_success 'multiple identical conflicts' '
 	# - six.1 replaces these 7s with 6.1
 	# - six.2 replaces these 7s with 6.2
 
-	test_must_fail git merge six.1 &&
+	merge_conflict_resolve &&
 
 	# Check that rerere knows that file1 and file2 have conflicts
-
 	printf "%s\n" file1 file2 >expect &&
 	git ls-files -u | sed -e "s/^.*	//" | sort -u >actual &&
 	test_cmp expect actual &&
@@ -452,19 +484,43 @@ test_expect_success 'multiple identical conflicts' '
 	git rerere status | sort >actual &&
 	test_cmp expect actual &&
 
-	# Resolution is to replace 7 with 6.1 and 6.2 (i.e. take both)
-	concat_insert short 6.1 6.2 >file1 &&
-	concat_insert long 6.1 6.2 >file2 &&
-
 	git rerere remaining >actual &&
 	test_cmp expect actual &&
 
+	count_pre_post 2 0 &&
+
+	# Pretend that the conflicts were made quite some time ago
+	find .git/rr-cache/ -type f | xargs test-chmtime -172800 &&
+
+	# Unresolved entries have not expired yet
+	git -c gc.rerereresolved=5 -c gc.rerereunresolved=5 rerere gc &&
+	count_pre_post 2 0 &&
+
+	# Unresolved entries have expired
+	git -c gc.rerereresolved=5 -c gc.rerereunresolved=1 rerere gc &&
+	count_pre_post 0 0 &&
+
+	# Recreate the conflicted state
+	merge_conflict_resolve &&
+	count_pre_post 2 0 &&
+
+	# Clear it
+	git rerere clear &&
+	count_pre_post 0 0 &&
+
+	# Recreate the conflicted state
+	merge_conflict_resolve &&
+	count_pre_post 2 0 &&
+
 	# We resolved file1 and file2
 	git rerere &&
 	>expect &&
 	git rerere remaining >actual &&
 	test_cmp expect actual &&
 
+	# We must have recorded both of them
+	count_pre_post 2 2 &&
+
 	# Now we should be able to resolve them both
 	git reset --hard &&
 	test_must_fail git merge six.1 &&
@@ -477,7 +533,19 @@ test_expect_success 'multiple identical conflicts' '
 	concat_insert short 6.1 6.2 >file1.expect &&
 	concat_insert long 6.1 6.2 >file2.expect &&
 	test_cmp file1.expect file1 &&
-	test_cmp file2.expect file2
+	test_cmp file2.expect file2 &&
+
+	# Pretend again
+	find .git/rr-cache/ -type f | xargs test-chmtime -172800 &&
+
+	# Resolved entries have not expired yet
+	git -c gc.rerereresolved=5 -c gc.rerereunresolved=5 rerere gc &&
+
+	count_pre_post 2 2 &&
+
+	# Resolved entries have expired
+	git -c gc.rerereresolved=1 -c gc.rerereunresolved=5 rerere gc &&
+	count_pre_post 0 0
 '
 
 test_done

diff --git a/rerere.c b/rerere.c
index 3d4dd33..2b870e0 100644
--- a/rerere.c
+++ b/rerere.c
@@ -517,103 +517,6 @@ static int handle_file(const char *path, unsigned char *sha1, const char *output
 }
 
 /*
- * Subclass of rerere_io that reads from an in-core buffer that is a
- * strbuf
- */
-struct rerere_io_mem {
-	struct rerere_io io;
-	struct strbuf input;
-};
-
-/*
- * ... and its getline() method implementation
- */
-static int rerere_mem_getline(struct strbuf *sb, struct rerere_io *io_)
-{
-	struct rerere_io_mem *io = (struct rerere_io_mem *)io_;
-	char *ep;
-	size_t len;
-
-	strbuf_release(sb);
-	if (!io->input.len)
-		return -1;
-	ep = memchr(io->input.buf, '\n', io->input.len);
-	if (!ep)
-		ep = io->input.buf + io->input.len;
-	else if (*ep == '\n')
-		ep++;
-	len = ep - io->input.buf;
-	strbuf_add(sb, io->input.buf, len);
-	strbuf_remove(&io->input, 0, len);
-	return 0;
-}
-
-static int handle_cache(const char *path, unsigned char *sha1, const char *output)
-{
-	mmfile_t mmfile[3] = {{NULL}};
-	mmbuffer_t result = {NULL, 0};
-	const struct cache_entry *ce;
-	int pos, len, i, hunk_no;
-	struct rerere_io_mem io;
-	int marker_size = ll_merge_marker_size(path);
-
-	/*
-	 * Reproduce the conflicted merge in-core
-	 */
-	len = strlen(path);
-	pos = cache_name_pos(path, len);
-	if (0 <= pos)
-		return -1;
-	pos = -pos - 1;
-
-	while (pos < active_nr) {
-		enum object_type type;
-		unsigned long size;
-
-		ce = active_cache[pos++];
-		if (ce_namelen(ce) != len || memcmp(ce->name, path, len))
-			break;
-		i = ce_stage(ce) - 1;
-		if (!mmfile[i].ptr) {
-			mmfile[i].ptr = read_sha1_file(ce->sha1, &type, &size);
-			mmfile[i].size = size;
-		}
-	}
-	for (i = 0; i < 3; i++)
-		if (!mmfile[i].ptr && !mmfile[i].size)
-			mmfile[i].ptr = xstrdup("");
-
-	/*
-	 * NEEDSWORK: handle conflicts from merges with
-	 * merge.renormalize set, too
-	 */
-	ll_merge(&result, path, &mmfile[0], NULL,
-		 &mmfile[1], "ours",
-		 &mmfile[2], "theirs", NULL);
-	for (i = 0; i < 3; i++)
-		free(mmfile[i].ptr);
-
-	memset(&io, 0, sizeof(io));
-	io.io.getline = rerere_mem_getline;
-	if (output)
-		io.io.output = fopen(output, "w");
-	else
-		io.io.output = NULL;
-	strbuf_init(&io.input, 0);
-	strbuf_attach(&io.input, result.ptr, result.size, result.size);
-
-	/*
-	 * Grab the conflict ID and optionally write the original
-	 * contents with conflict markers out.
-	 */
-	hunk_no = handle_path(sha1, (struct rerere_io *)&io, marker_size);
-	strbuf_release(&io.input);
-	if (io.io.output)
-		fclose(io.io.output);
-	return hunk_no;
-}
-
-/*
  * Look at a cache entry at "i" and see if it is not conflicting,
  * conflicting and we are willing to handle, or conflicting and
  * we are unable to handle, and return the determination in *type.
@@ -1005,6 +908,103 @@ int rerere(int flags)
 	return status;
 }
 
+/*
+ * Subclass of rerere_io that reads from an in-core buffer that is a
+ * strbuf
+ */
+struct rerere_io_mem {
+	struct rerere_io io;
+	struct strbuf input;
+};
+
+/*
+ * ... and its getline() method implementation
+ */
+static int rerere_mem_getline(struct strbuf *sb, struct rerere_io *io_)
+{
+	struct rerere_io_mem *io = (struct rerere_io_mem *)io_;
+	char *ep;
+	size_t len;
+
+	strbuf_release(sb);
+	if (!io->input.len)
+		return -1;
+	ep = memchr(io->input.buf, '\n', io->input.len);
+	if (!ep)
+		ep = io->input.buf + io->input.len;
+	else if (*ep == '\n')
+		ep++;
+	len = ep - io->input.buf;
+	strbuf_add(sb, io->input.buf, len);
+	strbuf_remove(&io->input, 0, len);
+	return 0;
+}
+
+static int handle_cache(const char *path, unsigned char *sha1, const char *output)
+{
+	mmfile_t mmfile[3] = {{NULL}};
+	mmbuffer_t result = {NULL, 0};
+	const struct cache_entry *ce;
+	int pos, len, i, hunk_no;
+	struct rerere_io_mem io;
+	int marker_size = ll_merge_marker_size(path);
+
+	/*
+	 * Reproduce the conflicted merge in-core
+	 */
+	len = strlen(path);
+	pos = cache_name_pos(path, len);
+	if (0 <= pos)
+		return -1;
+	pos = -pos - 1;
+
+	while (pos < active_nr) {
+		enum object_type type;
+		unsigned long size;
+
+		ce = active_cache[pos++];
+		if (ce_namelen(ce) != len || memcmp(ce->name, path, len))
+			break;
+		i = ce_stage(ce) - 1;
+		if (!mmfile[i].ptr) {
+			mmfile[i].ptr = read_sha1_file(ce->sha1, &type, &size);
+			mmfile[i].size = size;
+		}
+	}
+	for (i = 0; i < 3; i++)
+		if (!mmfile[i].ptr && !mmfile[i].size)
+			mmfile[i].ptr = xstrdup("");
+
+	/*
+	 * NEEDSWORK: handle conflicts from merges with
+	 * merge.renormalize set, too?
+	 */
+	ll_merge(&result, path, &mmfile[0], NULL,
+		 &mmfile[1], "ours",
+		 &mmfile[2], "theirs", NULL);
+	for (i = 0; i < 3; i++)
+		free(mmfile[i].ptr);
+
+	memset(&io, 0, sizeof(io));
+	io.io.getline = rerere_mem_getline;
+	if (output)
+		io.io.output = fopen(output, "w");
+	else
+		io.io.output = NULL;
+	strbuf_init(&io.input, 0);
+	strbuf_attach(&io.input, result.ptr, result.size, result.size);
+
+	/*
+	 * Grab the conflict ID and optionally write the original
+	 * contents with conflict markers out.
+	 */
+	hunk_no = handle_path(sha1, (struct rerere_io *)&io, marker_size);
+	strbuf_release(&io.input);
+	if (io.io.output)
+		fclose(io.io.output);
+	return hunk_no;
+}
+
 static int rerere_forget_one_path(const char *path, struct string_list *rr)
 {
 	const char *filename;

diff --git a/rerere.c b/rerere.c
index 2b870e0..e636d4b 100644
--- a/rerere.c
+++ b/rerere.c
@@ -622,6 +622,33 @@ int rerere_remaining(struct string_list *merge_rr)
 }
 
 /*
+ * Try using the given conflict resolution "ID" to see
+ * if that recorded conflict resolves cleanly what we
+ * got in the "cur".
+ */
+static int try_merge(const struct rerere_id *id, const char *path,
+		     mmfile_t *cur, mmbuffer_t *result)
+{
+	int ret;
+	mmfile_t base = {NULL, 0}, other = {NULL, 0};
+
+	if (read_mmfile(&base, rerere_path(id, "preimage")) ||
+	    read_mmfile(&other, rerere_path(id, "postimage")))
+		ret = 1;
+	else
+		/*
+		 * A three-way merge. Note that this honors user-customizable
+		 * low-level merge driver settings.
+		 */
+		ret = ll_merge(result, path, &base, NULL, cur, "", &other, "", NULL);
+
+	free(base.ptr);
+	free(other.ptr);
+
+	return ret;
+}
+
+/*
  * Find the conflict identified by "id"; the change between its
  * "preimage" (i.e. a previous contents with conflict markers) and its
  * "postimage" (i.e. the corresponding contents with conflicts
@@ -635,30 +662,20 @@ static int merge(const struct rerere_id *id, const char *path)
 {
 	FILE *f;
 	int ret;
-	mmfile_t cur = {NULL, 0}, base = {NULL, 0}, other = {NULL, 0};
+	mmfile_t cur = {NULL, 0};
 	mmbuffer_t result = {NULL, 0};
 
 	/*
 	 * Normalize the conflicts in path and write it out to
 	 * "thisimage" temporary file.
 	 */
-	if (handle_file(path, NULL, rerere_path(id, "thisimage")) < 0) {
-		ret = 1;
-		goto out;
-	}
-
-	if (read_mmfile(&cur, rerere_path(id, "thisimage")) ||
-	    read_mmfile(&base, rerere_path(id, "preimage")) ||
-	    read_mmfile(&other, rerere_path(id, "postimage"))) {
+	if ((handle_file(path, NULL, rerere_path(id, "thisimage")) < 0) ||
+	    read_mmfile(&cur, rerere_path(id, "thisimage"))) {
 		ret = 1;
 		goto out;
 	}
 
-	/*
-	 * A three-way merge. Note that this honors user-customizable
-	 * low-level merge driver settings.
-	 */
-	ret = ll_merge(&result, path, &base, NULL, &cur, "", &other, "", NULL);
+	ret = try_merge(id, path, &cur, &result);
 	if (ret)
 		goto out;
 
@@ -684,8 +701,6 @@ static int merge(const struct rerere_id *id, const char *path)
 
 out:
 	free(cur.ptr);
-	free(base.ptr);
-	free(other.ptr);
 	free(result.ptr);
 
 	return ret;

diff --git a/rerere.c b/rerere.c
index e636d4b..1693866 100644
--- a/rerere.c
+++ b/rerere.c
@@ -1038,7 +1038,33 @@ static int rerere_forget_one_path(const char *path, struct string_list *rr)
 
 	/* Nuke the recorded resolution for the conflict */
 	id = new_rerere_id(sha1);
-	id->variant = 0; /* for now */
+
+	for (id->variant = 0;
+	     id->variant < id->collection->status_nr;
+	     id->variant++) {
+		mmfile_t cur = { NULL, 0 };
+		mmbuffer_t result = {NULL, 0};
+		int cleanly_resolved;
+
+		if (!has_rerere_resolution(id))
+			continue;
+
+		handle_cache(path, sha1, rerere_path(id, "thisimage"));
+		if (read_mmfile(&cur, rerere_path(id, "thisimage"))) {
+			free(cur.ptr);
+			return error("Failed to update conflicted state in '%s'",
+				     path);
+		}
+		cleanly_resolved = !try_merge(id, path, &cur, &result);
+		free(result.ptr);
+		free(cur.ptr);
+		if (cleanly_resolved)
+			break;
+	}
+
+	if (id->collection->status_nr <= id->variant)
+		return error("no remembered resolution for '%s'", path);
+
 	filename = rerere_path(id, "postimage");
 	if (unlink(filename))
 		return (errno == ENOENT

rerere.c, rerere.h

diff --git a/rerere.c b/rerere.c
index 3d0fa8f..a5d8a06 100644
--- a/rerere.c
+++ b/rerere.c
@@ -8,6 +8,7 @@
 #include "ll-merge.h"
 #include "attr.h"
 #include "pathspec.h"
+#include "sha1-lookup.h"
 
 #define RESOLVED 0
 #define PUNTED 1
@@ -22,6 +23,23 @@ static int rerere_autoupdate;
 
 static char *merge_rr_path;
 
+static int rerere_dir_nr;
+static int rerere_dir_alloc;
+
+static struct rerere_dir {
+	unsigned char sha1[20];
+} **rerere_dir;
+
+static void free_rerere_dirs(void)
+{
+	int i;
+	for (i = 0; i < rerere_dir_nr; i++)
+		free(rerere_dir[i]);
+	free(rerere_dir);
+	rerere_dir_nr = rerere_dir_alloc = 0;
+	rerere_dir = NULL;
+}
+
 static void free_rerere_id(struct string_list_item *item)
 {
 	free(item->util);
@@ -29,7 +47,7 @@ static void free_rerere_id(struct string_list_item *item)
 
 static const char *rerere_id_hex(const struct rerere_id *id)
 {
-	return id->hex;
+	return sha1_to_hex(id->collection->sha1);
 }
 
 const char *rerere_path(const struct rerere_id *id, const char *file)
@@ -40,6 +58,37 @@ const char *rerere_path(const struct rerere_id *id, const char *file)
 	return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
 }
 
+static const unsigned char *rerere_dir_sha1(size_t i, void *table)
+{
+	struct rerere_dir **rr_dir = table;
+	return rr_dir[i]->sha1;
+}
+
+static struct rerere_dir *find_rerere_dir(const char *hex)
+{
+	unsigned char sha1[20];
+	struct rerere_dir *rr_dir;
+	int pos;
+
+	if (get_sha1_hex(hex, sha1))
+		return NULL; /* BUG */
+	pos = sha1_pos(sha1, rerere_dir, rerere_dir_nr, rerere_dir_sha1);
+	if (pos < 0) {
+		rr_dir = xmalloc(sizeof(*rr_dir));
+		hashcpy(rr_dir->sha1, sha1);
+		pos = -1 - pos;
+
+		/* Make sure the array is big enough ... */
+		ALLOC_GROW(rerere_dir, rerere_dir_nr + 1, rerere_dir_alloc);
+		/* ... and add it in. */
+		rerere_dir_nr++;
+		memmove(rerere_dir + pos + 1, rerere_dir + pos,
+			(rerere_dir_nr - pos - 1) * sizeof(*rerere_dir));
+		rerere_dir[pos] = rr_dir;
+	}
+	return rerere_dir[pos];
+}
+
 static int has_rerere_resolution(const struct rerere_id *id)
 {
 	struct stat st;
@@ -50,7 +99,7 @@ static int has_rerere_resolution(const struct rerere_id *id)
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
-	xsnprintf(id->hex, sizeof(id->hex), "%s", hex);
+	id->collection = find_rerere_dir(hex);
 	return id;
 }
 
@@ -810,12 +859,14 @@ int setup_rerere(struct string_list *merge_rr, int flags)
 int rerere(int flags)
 {
 	struct string_list merge_rr = STRING_LIST_INIT_DUP;
-	int fd;
+	int fd, status;
 
 	fd = setup_rerere(&merge_rr, flags);
 	if (fd < 0)
 		return 0;
-	return do_plain_rerere(&merge_rr, fd);
+	status = do_plain_rerere(&merge_rr, fd);
+	free_rerere_dirs();
+	return status;
 }
 
 static int rerere_forget_one_path(const char *path, struct string_list *rr)
@@ -900,7 +951,7 @@ int rerere_forget(struct pathspec *pathspec)
 static struct rerere_id *dirname_to_id(const char *name)
 {
 	static struct rerere_id id;
-	xsnprintf(id.hex, sizeof(id.hex), "%s", name);
+	id.collection = find_rerere_dir(name);
 	return &id;
 }
 
diff --git a/rerere.h b/rerere.h
index ce545d0..faf5a23 100644
--- a/rerere.h
+++ b/rerere.h
@@ -15,8 +15,9 @@ struct pathspec;
  */
 extern void *RERERE_RESOLVED;
 
+struct rerere_dir;
 struct rerere_id {
-	char hex[41];
+	struct rerere_dir *collection;
 };
 
 extern int setup_rerere(struct string_list *, int);

diff --git a/rerere.c b/rerere.c
index a5d8a06..fbdade8 100644
--- a/rerere.c
+++ b/rerere.c
@@ -26,8 +26,11 @@ static char *merge_rr_path;
 static int rerere_dir_nr;
 static int rerere_dir_alloc;
 
+#define RR_HAS_POSTIMAGE 1
+#define RR_HAS_PREIMAGE 2
 static struct rerere_dir {
 	unsigned char sha1[20];
+	unsigned char status;
 } **rerere_dir;
 
 static void free_rerere_dirs(void)
@@ -58,6 +61,27 @@ const char *rerere_path(const struct rerere_id *id, const char *file)
 	return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
 }
 
+static int is_rr_file(const char *name, const char *filename)
+{
+	return !strcmp(name, filename);
+}
+
+static void scan_rerere_dir(struct rerere_dir *rr_dir)
+{
+	struct dirent *de;
+	DIR *dir = opendir(git_path("rr-cache/%s", sha1_to_hex(rr_dir->sha1)));
+
+	if (!dir)
+		return;
+	while ((de = readdir(dir)) != NULL) {
+		if (is_rr_file(de->d_name, "postimage"))
+			rr_dir->status |= RR_HAS_POSTIMAGE;
+		else if (is_rr_file(de->d_name, "preimage"))
+			rr_dir->status |= RR_HAS_PREIMAGE;
+	}
+	closedir(dir);
+}
+
 static const unsigned char *rerere_dir_sha1(size_t i, void *table)
 {
 	struct rerere_dir **rr_dir = table;
@@ -76,6 +100,7 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 	if (pos < 0) {
 		rr_dir = xmalloc(sizeof(*rr_dir));
 		hashcpy(rr_dir->sha1, sha1);
+		rr_dir->status = 0;
 		pos = -1 - pos;
 
 		/* Make sure the array is big enough ... */
@@ -85,15 +110,14 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 		memmove(rerere_dir + pos + 1, rerere_dir + pos,
 			(rerere_dir_nr - pos - 1) * sizeof(*rerere_dir));
 		rerere_dir[pos] = rr_dir;
+		scan_rerere_dir(rr_dir);
 	}
 	return rerere_dir[pos];
 }
 
 static int has_rerere_resolution(const struct rerere_id *id)
 {
-	struct stat st;
-
-	return !stat(rerere_path(id, "postimage"), &st);
+	return (id->collection->status & RR_HAS_POSTIMAGE);
 }
 
 static struct rerere_id *new_rerere_id_hex(char *hex)
@@ -737,6 +761,7 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 	} else if (!handle_file(path, NULL, NULL)) {
 		/* The user has resolved it. */
 		copy_file(rerere_path(id, "postimage"), path, 0666);
+		id->collection->status |= RR_HAS_POSTIMAGE;
 		fprintf(stderr, "Recorded resolution for '%s'.\n", path);
 	} else {
 		return;
@@ -797,6 +822,7 @@ static int do_plain_rerere(struct string_list *rr, int fd)
 		 * normalized contents to the "preimage" file.
 		 */
 		handle_file(path, NULL, rerere_path(id, "preimage"));
+		id->collection->status |= RR_HAS_PREIMAGE;
 		fprintf(stderr, "Recorded preimage for '%s'\n", path);
 	}
 

rerere.c, t/t4200-rerere.sh

diff --git a/rerere.c b/rerere.c
index fbdade8..a1e2963 100644
--- a/rerere.c
+++ b/rerere.c
@@ -117,7 +117,9 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 
 static int has_rerere_resolution(const struct rerere_id *id)
 {
-	return (id->collection->status & RR_HAS_POSTIMAGE);
+	const int both = RR_HAS_POSTIMAGE|RR_HAS_PREIMAGE;
+
+	return ((id->collection->status & both) == both);
 }
 
 static struct rerere_id *new_rerere_id_hex(char *hex)
@@ -806,24 +808,30 @@ static int do_plain_rerere(struct string_list *rr, int fd)
 		string_list_insert(rr, path)->util = id;
 
 		/*
-		 * If the directory does not exist, create
-		 * it.  mkdir_in_gitdir() will fail with
-		 * EEXIST if there already is one.
-		 *
-		 * NEEDSWORK: make sure "gc" does not remove
-		 * preimage without removing the directory.
+		 * Ensure that the directory exists.
+		 * mkdir_in_gitdir() will fail with EEXIST if there
+		 * already is one.
 		 */
-		if (mkdir_in_gitdir(rerere_path(id, NULL)))
-			continue;
+		if (mkdir_in_gitdir(rerere_path(id, NULL)) &&
+		    errno != EEXIST)
+			continue; /* NEEDSWORK: perhaps we should die? */
 
-		/*
-		 * We are the first to encounter this
-		 * conflict.  Ask handle_file() to write the
-		 * normalized contents to the "preimage" file.
-		 */
-		handle_file(path, NULL, rerere_path(id, "preimage"));
-		id->collection->status |= RR_HAS_PREIMAGE;
-		fprintf(stderr, "Recorded preimage for '%s'\n", path);
+		if (id->collection->status & RR_HAS_PREIMAGE) {
+			;
+		} else {
+			/*
+			 * We are the first to encounter this
+			 * conflict.  Ask handle_file() to write the
+			 * normalized contents to the "preimage" file.
+			 *
+			 * NEEDSWORK: what should happen if we had a
+			 * leftover postimage that is totally
+			 * unrelated?  Perhaps we should unlink it?
+			 */
+			handle_file(path, NULL, rerere_path(id, "preimage"));
+			id->collection->status |= RR_HAS_PREIMAGE;
+			fprintf(stderr, "Recorded preimage for '%s'\n", path);
+		}
 	}
 
 	for (i = 0; i < rr->nr; i++)
diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index ed9c91e..c428011 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -184,12 +184,27 @@ test_expect_success 'rerere updates postimage timestamp' '
 '
 
 test_expect_success 'rerere clear' '
-	rm $rr/postimage &&
+	mv $rr/postimage .git/post-saved &&
 	echo "$sha1	a1" | perl -pe "y/\012/\000/" >.git/MERGE_RR &&
 	git rerere clear &&
 	! test -d $rr
 '
 
+test_expect_success 'leftover directory' '
+	git reset --hard &&
+	mkdir -p $rr &&
+	test_must_fail git merge first &&
+	test -f $rr/preimage
+'
+
+test_expect_success 'missing preimage' '
+	git reset --hard &&
+	mkdir -p $rr &&
+	cp .git/post-saved $rr/postimage &&
+	test_must_fail git merge first &&
+	test -f $rr/preimage
+'
+
 test_expect_success 'set up for garbage collection tests' '
 	mkdir -p $rr &&
 	echo Hello >$rr/preimage &&

diff --git a/rerere.c b/rerere.c
index a1e2963..33b1348 100644
--- a/rerere.c
+++ b/rerere.c
@@ -122,6 +122,11 @@ static int has_rerere_resolution(const struct rerere_id *id)
 	return ((id->collection->status & both) == both);
 }
 
+static int has_rerere_preimage(const struct rerere_id *id)
+{
+	return (id->collection->status & RR_HAS_PREIMAGE);
+}
+
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
@@ -749,8 +754,24 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 	const char *path = rr_item->string;
 	const struct rerere_id *id = rr_item->util;
 
-	/* Is there a recorded resolution we could attempt to apply? */
-	if (has_rerere_resolution(id)) {
+	if (!has_rerere_preimage(id)) {
+		/*
+		 * We are the first to encounter this conflict.  Ask
+		 * handle_file() to write the normalized contents to
+		 * the "preimage" file.
+		 */
+		handle_file(path, NULL, rerere_path(id, "preimage"));
+		if (id->collection->status & RR_HAS_POSTIMAGE) {
+			const char *path = rerere_path(id, "postimage");
+			if (unlink(path))
+				die_errno("cannot unlink stray '%s'", path);
+			id->collection->status &= ~RR_HAS_POSTIMAGE;
+		}
+		id->collection->status |= RR_HAS_PREIMAGE;
+		fprintf(stderr, "Recorded preimage for '%s'\n", path);
+		return;
+	} else if (has_rerere_resolution(id)) {
+		/* Is there a recorded resolution we could attempt to apply? */
 		if (merge(id, path))
 			return; /* failed to replay */
 
@@ -807,31 +828,8 @@ static int do_plain_rerere(struct string_list *rr, int fd)
 		id = new_rerere_id(sha1);
 		string_list_insert(rr, path)->util = id;
 
-		/*
-		 * Ensure that the directory exists.
-		 * mkdir_in_gitdir() will fail with EEXIST if there
-		 * already is one.
-		 */
-		if (mkdir_in_gitdir(rerere_path(id, NULL)) &&
-		    errno != EEXIST)
-			continue; /* NEEDSWORK: perhaps we should die? */
-
-		if (id->collection->status & RR_HAS_PREIMAGE) {
-			;
-		} else {
-			/*
-			 * We are the first to encounter this
-			 * conflict.  Ask handle_file() to write the
-			 * normalized contents to the "preimage" file.
-			 *
-			 * NEEDSWORK: what should happen if we had a
-			 * leftover postimage that is totally
-			 * unrelated?  Perhaps we should unlink it?
-			 */
-			handle_file(path, NULL, rerere_path(id, "preimage"));
-			id->collection->status |= RR_HAS_PREIMAGE;
-			fprintf(stderr, "Recorded preimage for '%s'\n", path);
-		}
+		/* Ensure that the directory exists. */
+		mkdir_in_gitdir(rerere_path(id, NULL));
 	}
 
 	for (i = 0; i < rr->nr; i++)

rerere.c, rerere.h

diff --git a/rerere.c b/rerere.c
index 33b1348..0cf857b 100644
--- a/rerere.c
+++ b/rerere.c
@@ -30,14 +30,17 @@ static int rerere_dir_alloc;
 #define RR_HAS_PREIMAGE 2
 static struct rerere_dir {
 	unsigned char sha1[20];
-	unsigned char status;
+	int status_alloc, status_nr;
+	unsigned char *status;
 } **rerere_dir;
 
 static void free_rerere_dirs(void)
 {
 	int i;
-	for (i = 0; i < rerere_dir_nr; i++)
+	for (i = 0; i < rerere_dir_nr; i++) {
+		free(rerere_dir[i]->status);
 		free(rerere_dir[i]);
+	}
 	free(rerere_dir);
 	rerere_dir_nr = rerere_dir_alloc = 0;
 	rerere_dir = NULL;
@@ -53,17 +56,59 @@ static const char *rerere_id_hex(const struct rerere_id *id)
 	return sha1_to_hex(id->collection->sha1);
 }
 
+static void fit_variant(struct rerere_dir *rr_dir, int variant)
+{
+	variant++;
+	ALLOC_GROW(rr_dir->status, variant, rr_dir->status_alloc);
+	if (rr_dir->status_nr < variant) {
+		memset(rr_dir->status + rr_dir->status_nr,
+		       '\0', variant - rr_dir->status_nr);
+		rr_dir->status_nr = variant;
+	}
+}
+
+static void assign_variant(struct rerere_id *id)
+{
+	int variant;
+	struct rerere_dir *rr_dir = id->collection;
+
+	variant = id->variant;
+	if (variant < 0) {
+		variant = 0; /* for now */
+	}
+	fit_variant(rr_dir, variant);
+	id->variant = variant;
+}
+
 const char *rerere_path(const struct rerere_id *id, const char *file)
 {
 	if (!file)
 		return git_path("rr-cache/%s", rerere_id_hex(id));
 
-	return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
+	if (id->variant <= 0)
+		return git_path("rr-cache/%s/%s", rerere_id_hex(id), file);
+
+	return git_path("rr-cache/%s/%s.%d",
+			rerere_id_hex(id), file, id->variant);
 }
 
-static int is_rr_file(const char *name, const char *filename)
+static int is_rr_file(const char *name, const char *filename, int *variant)
 {
-	return !strcmp(name, filename);
+	const char *suffix;
+	char *ep;
+
+	if (!strcmp(name, filename)) {
+		*variant = 0;
+		return 1;
+	}
+	if (!skip_prefix(name, filename, &suffix) || *suffix != '.')
+		return 0;
+
+	errno = 0;
+	*variant = strtol(suffix + 1, &ep, 10);
+	if (errno || *ep)
+		return 0;
+	return 1;
 }
 
 static void scan_rerere_dir(struct rerere_dir *rr_dir)
@@ -74,10 +119,15 @@ static void scan_rerere_dir(struct rerere_dir *rr_dir)
 	if (!dir)
 		return;
 	while ((de = readdir(dir)) != NULL) {
-		if (is_rr_file(de->d_name, "postimage"))
-			rr_dir->status |= RR_HAS_POSTIMAGE;
-		else if (is_rr_file(de->d_name, "preimage"))
-			rr_dir->status |= RR_HAS_PREIMAGE;
+		int variant;
+
+		if (is_rr_file(de->d_name, "postimage", &variant)) {
+			fit_variant(rr_dir, variant);
+			rr_dir->status[variant] |= RR_HAS_POSTIMAGE;
+		} else if (is_rr_file(de->d_name, "preimage", &variant)) {
+			fit_variant(rr_dir, variant);
+			rr_dir->status[variant] |= RR_HAS_PREIMAGE;
+		}
 	}
 	closedir(dir);
 }
@@ -100,7 +150,9 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 	if (pos < 0) {
 		rr_dir = xmalloc(sizeof(*rr_dir));
 		hashcpy(rr_dir->sha1, sha1);
-		rr_dir->status = 0;
+		rr_dir->status = NULL;
+		rr_dir->status_nr = 0;
+		rr_dir->status_alloc = 0;
 		pos = -1 - pos;
 
 		/* Make sure the array is big enough ... */
@@ -118,19 +170,27 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 static int has_rerere_resolution(const struct rerere_id *id)
 {
 	const int both = RR_HAS_POSTIMAGE|RR_HAS_PREIMAGE;
+	int variant = id->variant;
 
-	return ((id->collection->status & both) == both);
+	if (variant < 0)
+		return 0;
+	return ((id->collection->status[variant] & both) == both);
 }
 
 static int has_rerere_preimage(const struct rerere_id *id)
 {
-	return (id->collection->status & RR_HAS_PREIMAGE);
+	int variant = id->variant;
+
+	if (variant < 0)
+		return 0;
+	return (id->collection->status[variant] & RR_HAS_PREIMAGE);
 }
 
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
 	id->collection = find_rerere_dir(hex);
+	id->variant = -1; /* not known yet */
 	return id;
 }
 
@@ -157,16 +217,26 @@ static void read_rr(struct string_list *rr)
 		char *path;
 		unsigned char sha1[20];
 		struct rerere_id *id;
+		int variant;
 
 		/* There has to be the hash, tab, path and then NUL */
 		if (buf.len < 42 || get_sha1_hex(buf.buf, sha1))
 			die("corrupt MERGE_RR");
 
-		if (buf.buf[40] != '\t')
+		if (buf.buf[40] != '.') {
+			variant = 0;
+			path = buf.buf + 40;
+		} else {
+			errno = 0;
+			variant = strtol(buf.buf + 41, &path, 10);
+			if (errno)
+				die("corrupt MERGE_RR");
+		}
+		if (*(path++) != '\t')
 			die("corrupt MERGE_RR");
 		buf.buf[40] = '\0';
-		path = buf.buf + 41;
 		id = new_rerere_id_hex(buf.buf);
+		id->variant = variant;
 		string_list_insert(rr, path)->util = id;
 	}
 	strbuf_release(&buf);
@@ -187,9 +257,16 @@ static int write_rr(struct string_list *rr, int out_fd)
 		id = rr->items[i].util;
 		if (!id)
 			continue;
-		strbuf_addf(&buf, "%s\t%s%c",
-			    rerere_id_hex(id),
-			    rr->items[i].string, 0);
+		assert(id->variant >= 0);
+		if (0 < id->variant)
+			strbuf_addf(&buf, "%s.%d\t%s%c",
+				    rerere_id_hex(id), id->variant,
+				    rr->items[i].string, 0);
+		else
+			strbuf_addf(&buf, "%s\t%s%c",
+				    rerere_id_hex(id),
+				    rr->items[i].string, 0);
+
 		if (write_in_full(out_fd, buf.buf, buf.len) != buf.len)
 			die("unable to write rerere record");
 
@@ -752,7 +829,12 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 			       struct string_list *update)
 {
 	const char *path = rr_item->string;
-	const struct rerere_id *id = rr_item->util;
+	struct rerere_id *id = rr_item->util;
+	int variant;
+
+	if (id->variant < 0)
+		assign_variant(id);
+	variant = id->variant;
 
 	if (!has_rerere_preimage(id)) {
 		/*
@@ -761,13 +843,13 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 		 * the "preimage" file.
 		 */
 		handle_file(path, NULL, rerere_path(id, "preimage"));
-		if (id->collection->status & RR_HAS_POSTIMAGE) {
+		if (id->collection->status[variant] & RR_HAS_POSTIMAGE) {
 			const char *path = rerere_path(id, "postimage");
 			if (unlink(path))
 				die_errno("cannot unlink stray '%s'", path);
-			id->collection->status &= ~RR_HAS_POSTIMAGE;
+			id->collection->status[variant] &= ~RR_HAS_POSTIMAGE;
 		}
-		id->collection->status |= RR_HAS_PREIMAGE;
+		id->collection->status[variant] |= RR_HAS_PREIMAGE;
 		fprintf(stderr, "Recorded preimage for '%s'\n", path);
 		return;
 	} else if (has_rerere_resolution(id)) {
@@ -784,7 +866,7 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 	} else if (!handle_file(path, NULL, NULL)) {
 		/* The user has resolved it. */
 		copy_file(rerere_path(id, "postimage"), path, 0666);
-		id->collection->status |= RR_HAS_POSTIMAGE;
+		id->collection->status[variant] |= RR_HAS_POSTIMAGE;
 		fprintf(stderr, "Recorded resolution for '%s'.\n", path);
 	} else {
 		return;
@@ -919,6 +1001,7 @@ static int rerere_forget_one_path(const char *path, struct string_list *rr)
 
 	/* Nuke the recorded resolution for the conflict */
 	id = new_rerere_id(sha1);
+	id->variant = 0; /* for now */
 	filename = rerere_path(id, "postimage");
 	if (unlink(filename))
 		return (errno == ENOENT
diff --git a/rerere.h b/rerere.h
index faf5a23..64d38d9 100644
--- a/rerere.h
+++ b/rerere.h
@@ -18,6 +18,7 @@ extern void *RERERE_RESOLVED;
 struct rerere_dir;
 struct rerere_id {
 	struct rerere_dir *collection;
+	int variant;
 };
 
 extern int setup_rerere(struct string_list *, int);

diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index c428011..6fcc6d4 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -406,4 +406,78 @@ test_expect_success 'rerere -h' '
 	test_i18ngrep [Uu]sage help
 '
 
+concat_insert () {
+	last=$1
+	shift
+	cat early && printf "%s\n" "$@" && cat late "$last"
+}
+
+test_expect_failure 'multiple identical conflicts' '
+	git reset --hard &&
+
+	test_seq 1 6 >early &&
+	>late &&
+	test_seq 11 15 >short &&
+	test_seq 111 120 >long &&
+	concat_insert short >file1 &&
+	concat_insert long >file2 &&
+	git add file1 file2 &&
+	git commit -m base &&
+	git tag base &&
+	git checkout -b six.1 &&
+	concat_insert short 6.1 >file1 &&
+	concat_insert long 6.1 >file2 &&
+	git add file1 file2 &&
+	git commit -m 6.1 &&
+	git checkout -b six.2 HEAD^ &&
+	concat_insert short 6.2 >file1 &&
+	concat_insert long 6.2 >file2 &&
+	git add file1 file2 &&
+	git commit -m 6.2 &&
+
+	# At this point, six.1 and six.2
+	# - derive from common ancestor that has two files
+	#   1...6 7 11..15 (file1) and 1...6 7 111..120 (file2)
+	# - six.1 replaces these 7s with 6.1
+	# - six.2 replaces these 7s with 6.2
+
+	test_must_fail git merge six.1 &&
+
+	# Check that rerere knows that file1 and file2 have conflicts
+
+	printf "%s\n" file1 file2 >expect &&
+	git ls-files -u | sed -e "s/^.*	//" | sort -u >actual &&
+	test_cmp expect actual &&
+
+	git rerere status | sort >actual &&
+	test_cmp expect actual &&
+
+	# Resolution is to replace 7 with 6.1 and 6.2 (i.e. take both)
+	concat_insert short 6.1 6.2 >file1 &&
+	concat_insert long 6.1 6.2 >file2 &&
+
+	git rerere remaining >actual &&
+	test_cmp expect actual &&
+
+	# We resolved file1 and file2
+	git rerere &&
+	>expect &&
+	git rerere remaining >actual &&
+	test_cmp expect actual &&
+
+	# Now we should be able to resolve them both
+	git reset --hard &&
+	test_must_fail git merge six.1 &&
+	git rerere &&
+
+	>expect &&
+	git rerere remaining >actual &&
+	test_cmp expect actual &&
+
+	concat_insert short 6.1 6.2 >file1.expect &&
+	concat_insert long 6.1 6.2 >file2.expect &&
+	test_cmp file1.expect file1 &&
+	test_cmp file2.expect file2
+'
+
 test_done

rerere.c, t/t4200-rerere.sh

diff --git a/rerere.c b/rerere.c
index 0cf857b..353227c 100644
--- a/rerere.c
+++ b/rerere.c
@@ -74,7 +74,9 @@ static void assign_variant(struct rerere_id *id)
 
 	variant = id->variant;
 	if (variant < 0) {
-		variant = 0; /* for now */
+		for (variant = 0; variant < rr_dir->status_nr; variant++)
+			if (!rr_dir->status[variant])
+				break;
 	}
 	fit_variant(rr_dir, variant);
 	id->variant = variant;
@@ -177,15 +179,6 @@ static int has_rerere_resolution(const struct rerere_id *id)
 	return ((id->collection->status[variant] & both) == both);
 }
 
-static int has_rerere_preimage(const struct rerere_id *id)
-{
-	int variant = id->variant;
-
-	if (variant < 0)
-		return 0;
-	return (id->collection->status[variant] & RR_HAS_PREIMAGE);
-}
-
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
@@ -818,6 +811,13 @@ static void update_paths(struct string_list *update)
 		rollback_lock_file(&index_lock);
 }
 
+static void remove_variant(struct rerere_id *id)
+{
+	unlink_or_warn(rerere_path(id, "postimage"));
+	unlink_or_warn(rerere_path(id, "preimage"));
+	id->collection->status[id->variant] = 0;
+}
+
 /*
  * The path indicated by rr_item may still have conflict for which we
  * have a recorded resolution, in which case replay it and optionally
@@ -830,32 +830,46 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 {
 	const char *path = rr_item->string;
 	struct rerere_id *id = rr_item->util;
+	struct rerere_dir *rr_dir = id->collection;
 	int variant;
 
-	if (id->variant < 0)
-		assign_variant(id);
 	variant = id->variant;
 
-	if (!has_rerere_preimage(id)) {
+	/* Has the user resolved it already? */
+	if (variant >= 0) {
+		if (!handle_file(path, NULL, NULL)) {
+			copy_file(rerere_path(id, "postimage"), path, 0666);
+			id->collection->status[variant] |= RR_HAS_POSTIMAGE;
+			fprintf(stderr, "Recorded resolution for '%s'.\n", path);
+			free_rerere_id(rr_item);
+			rr_item->util = NULL;
+			return;
+		}
 		/*
-		 * We are the first to encounter this conflict.  Ask
-		 * handle_file() to write the normalized contents to
-		 * the "preimage" file.
+		 * There may be other variants that can cleanly
+		 * replay.  Try them and update the variant number for
+		 * this one.
 		 */
-		handle_file(path, NULL, rerere_path(id, "preimage"));
-		if (id->collection->status[variant] & RR_HAS_POSTIMAGE) {
-			const char *path = rerere_path(id, "postimage");
-			if (unlink(path))
-				die_errno("cannot unlink stray '%s'", path);
-			id->collection->status[variant] &= ~RR_HAS_POSTIMAGE;
-		}
-		id->collection->status[variant] |= RR_HAS_PREIMAGE;
-		fprintf(stderr, "Recorded preimage for '%s'\n", path);
-		return;
-	} else if (has_rerere_resolution(id)) {
-		/* Is there a recorded resolution we could attempt to apply? */
-		if (merge(id, path))
-			return; /* failed to replay */
+	}
+
+	/* Does any existing resolution apply cleanly? */
+	for (variant = 0; variant < rr_dir->status_nr; variant++) {
+		const int both = RR_HAS_PREIMAGE | RR_HAS_POSTIMAGE;
+		struct rerere_id vid = *id;
+
+		if ((rr_dir->status[variant] & both) != both)
+			continue;
+
+		vid.variant = variant;
+		if (merge(&vid, path))
+			continue; /* failed to replay */
+
+		/*
+		 * If there already is a different variant that applies
+		 * cleanly, there is no point maintaining our own variant.
+		 */
+		if (0 <= id->variant && id->variant != variant)
+			remove_variant(id);
 
 		if (rerere_autoupdate)
 			string_list_insert(update, path);
@@ -863,16 +877,24 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 			fprintf(stderr,
 				"Resolved '%s' using previous resolution.\n",
 				path);
-	} else if (!handle_file(path, NULL, NULL)) {
-		/* The user has resolved it. */
-		copy_file(rerere_path(id, "postimage"), path, 0666);
-		id->collection->status[variant] |= RR_HAS_POSTIMAGE;
-		fprintf(stderr, "Recorded resolution for '%s'.\n", path);
-	} else {
+		free_rerere_id(rr_item);
+		rr_item->util = NULL;
 		return;
 	}
-	free_rerere_id(rr_item);
-	rr_item->util = NULL;
+
+	/* None of the existing one applies; we need a new variant */
+	assign_variant(id);
+
+	variant = id->variant;
+	handle_file(path, NULL, rerere_path(id, "preimage"));
+	if (id->collection->status[variant] & RR_HAS_POSTIMAGE) {
+		const char *path = rerere_path(id, "postimage");
+		if (unlink(path))
+			die_errno("cannot unlink stray '%s'", path);
+		id->collection->status[variant] &= ~RR_HAS_POSTIMAGE;
+	}
+	id->collection->status[variant] |= RR_HAS_PREIMAGE;
+	fprintf(stderr, "Recorded preimage for '%s'\n", path);
 }
 
 static int do_plain_rerere(struct string_list *rr, int fd)
diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index 6fcc6d4..b1bda20 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -412,7 +412,7 @@ concat_insert () {
 	cat early && printf "%s\n" "$@" && cat late "$last"
 }
 
-test_expect_failure 'multiple identical conflicts' '
+test_expect_success 'multiple identical conflicts' '
 	git reset --hard &&
 
 	test_seq 1 6 >early &&

rerere.c, t/t4200-rerere.sh

diff --git a/rerere.c b/rerere.c
index 353227c..3d4dd33 100644
--- a/rerere.c
+++ b/rerere.c
@@ -1081,29 +1081,16 @@ int rerere_forget(struct pathspec *pathspec)
  * Garbage collection support
  */
 
-/*
- * Note that this is not reentrant but is used only one-at-a-time
- * so it does not matter right now.
- */
-static struct rerere_id *dirname_to_id(const char *name)
-{
-	static struct rerere_id id;
-	id.collection = find_rerere_dir(name);
-	return &id;
-}
-
-static time_t rerere_created_at(const char *dir_name)
+static time_t rerere_created_at(struct rerere_id *id)
 {
 	struct stat st;
-	struct rerere_id *id = dirname_to_id(dir_name);
 
 	return stat(rerere_path(id, "preimage"), &st) ? (time_t) 0 : st.st_mtime;
 }
 
-static time_t rerere_last_used_at(const char *dir_name)
+static time_t rerere_last_used_at(struct rerere_id *id)
 {
 	struct stat st;
-	struct rerere_id *id = dirname_to_id(dir_name);
 
 	return stat(rerere_path(id, "postimage"), &st) ? (time_t) 0 : st.st_mtime;
 }
@@ -1113,15 +1100,28 @@ static time_t rerere_last_used_at(const char *dir_name)
  */
 static void unlink_rr_item(struct rerere_id *id)
 {
-	unlink(rerere_path(id, "thisimage"));
-	unlink(rerere_path(id, "preimage"));
-	unlink(rerere_path(id, "postimage"));
-	/*
-	 * NEEDSWORK: what if this rmdir() fails?  Wouldn't we then
-	 * assume that we already have preimage recorded in
-	 * do_plain_rerere()?
-	 */
-	rmdir(rerere_path(id, NULL));
+	unlink_or_warn(rerere_path(id, "thisimage"));
+	remove_variant(id);
+	id->collection->status[id->variant] = 0;
+}
+
+static void prune_one(struct rerere_id *id, time_t now,
+		      int cutoff_resolve, int cutoff_noresolve)
+{
+	time_t then;
+	int cutoff;
+
+	then = rerere_last_used_at(id);
+	if (then)
+		cutoff = cutoff_resolve;
+	else {
+		then = rerere_created_at(id);
+		if (!then)
+			return;
+		cutoff = cutoff_noresolve;
+	}
+	if (then < now - cutoff * 86400)
+		unlink_rr_item(id);
 }
 
 void rerere_gc(struct string_list *rr)
@@ -1129,8 +1129,8 @@ void rerere_gc(struct string_list *rr)
 	struct string_list to_remove = STRING_LIST_INIT_DUP;
 	DIR *dir;
 	struct dirent *e;
-	int i, cutoff;
-	time_t now = time(NULL), then;
+	int i;
+	time_t now = time(NULL);
 	int cutoff_noresolve = 15;
 	int cutoff_resolve = 60;
 
@@ -1142,25 +1142,32 @@ void rerere_gc(struct string_list *rr)
 		die_errno("unable to open rr-cache directory");
 	/* Collect stale conflict IDs ... */
 	while ((e = readdir(dir))) {
+		struct rerere_dir *rr_dir;
+		struct rerere_id id;
+		int now_empty;
+
 		if (is_dot_or_dotdot(e->d_name))
 			continue;
-
-		then = rerere_last_used_at(e->d_name);
-		if (then) {
-			cutoff = cutoff_resolve;
-		} else {
-			then = rerere_created_at(e->d_name);
-			if (!then)
-				continue;
-			cutoff = cutoff_noresolve;
+		rr_dir = find_rerere_dir(e->d_name);
+		if (!rr_dir)
+			continue; /* or should we remove e->d_name? */
+
+		now_empty = 1;
+		for (id.variant = 0, id.collection = rr_dir;
+		     id.variant < id.collection->status_nr;
+		     id.variant++) {
+			prune_one(&id, now, cutoff_resolve, cutoff_noresolve);
+			if (id.collection->status[id.variant])
+				now_empty = 0;
 		}
-		if (then < now - cutoff * 86400)
+		if (now_empty)
 			string_list_append(&to_remove, e->d_name);
 	}
 	closedir(dir);
-	/* ... and then remove them one-by-one */
+
+	/* ... and then remove the empty directories */
 	for (i = 0; i < to_remove.nr; i++)
-		unlink_rr_item(dirname_to_id(to_remove.items[i].string));
+		rmdir(git_path("rr-cache/%s", to_remove.items[i].string));
 	string_list_clear(&to_remove, 0);
 }
 
@@ -1177,8 +1184,10 @@ void rerere_clear(struct string_list *merge_rr)
 
 	for (i = 0; i < merge_rr->nr; i++) {
 		struct rerere_id *id = merge_rr->items[i].util;
-		if (!has_rerere_resolution(id))
+		if (!has_rerere_resolution(id)) {
 			unlink_rr_item(id);
+			rmdir(rerere_path(id, NULL));
+		}
 	}
 	unlink_or_warn(git_path("MERGE_RR"));
 }
diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index b1bda20..a85fc7d 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -412,6 +412,39 @@ concat_insert () {
 	cat early && printf "%s\n" "$@" && cat late "$last"
 }
 
+count_pre_post () {
+	find .git/rr-cache/ -type f -name "preimage*" >actual &&
+	test_line_count = "$1" actual &&
+	find .git/rr-cache/ -type f -name "postimage*" >actual &&
+	test_line_count = "$2" actual
+}
+
+test_expect_success 'rerere gc' '
+	find .git/rr-cache -type f >original &&
+	xargs test-chmtime -172800 <original &&
+
+	git -c gc.rerereresolved=5 -c gc.rerereunresolved=5 rerere gc &&
+	find .git/rr-cache -type f >actual &&
+	test_cmp original actual &&
+
+	git -c gc.rerereresolved=5 -c gc.rerereunresolved=0 rerere gc &&
+	find .git/rr-cache -type f >actual &&
+	test_cmp original actual &&
+
+	git -c gc.rerereresolved=0 -c gc.rerereunresolved=0 rerere gc &&
+	find .git/rr-cache -type f >actual &&
+	>expect &&
+	test_cmp expect actual
+'
+
+merge_conflict_resolve () {
+	git reset --hard &&
+	test_must_fail git merge six.1 &&
+	# Resolution is to replace 7 with 6.1 and 6.2 (i.e. take both)
+	concat_insert short 6.1 6.2 >file1 &&
+	concat_insert long 6.1 6.2 >file2
+}
+
 test_expect_success 'multiple identical conflicts' '
 	git reset --hard &&
 
@@ -441,7 +474,7 @@ test_expect_success 'multiple identical conflicts' '
 	# - six.1 replaces these 7s with 6.1
 	# - six.2 replaces these 7s with 6.2
 
-	test_must_fail git merge six.1 &&
+	merge_conflict_resolve &&
 
 	# Check that rerere knows that file1 and file2 have conflicts
 
@@ -452,19 +485,43 @@ test_expect_success 'multiple identical conflicts' '
 	git rerere status | sort >actual &&
 	test_cmp expect actual &&
 
-	# Resolution is to replace 7 with 6.1 and 6.2 (i.e. take both)
-	concat_insert short 6.1 6.2 >file1 &&
-	concat_insert long 6.1 6.2 >file2 &&
-
 	git rerere remaining >actual &&
 	test_cmp expect actual &&
 
+	count_pre_post 2 0 &&
+
+	# Pretend that the conflicts were made quite some time ago
+	find .git/rr-cache/ -type f | xargs test-chmtime -172800 &&
+
+	# Unresolved entries have not expired yet
+	git -c gc.rerereresolved=5 -c gc.rerereunresolved=5 rerere gc &&
+	count_pre_post 2 0 &&
+
+	# Unresolved entries have expired
+	git -c gc.rerereresolved=5 -c gc.rerereunresolved=1 rerere gc &&
+	count_pre_post 0 0 &&
+
+	# Recreate the conflicted state
+	merge_conflict_resolve &&
+	count_pre_post 2 0 &&
+
+	# Clear it
+	git rerere clear &&
+	count_pre_post 0 0 &&
+
+	# Recreate the conflicted state
+	merge_conflict_resolve &&
+	count_pre_post 2 0 &&
+
 	# We resolved file1 and file2
 	git rerere &&
 	>expect &&
 	git rerere remaining >actual &&
 	test_cmp expect actual &&
 
+	# We must have recorded both of them
+	count_pre_post 2 2 &&
+
 	# Now we should be able to resolve them both
 	git reset --hard &&
 	test_must_fail git merge six.1 &&
@@ -477,7 +534,19 @@ test_expect_success 'multiple identical conflicts' '
 	concat_insert short 6.1 6.2 >file1.expect &&
 	concat_insert long 6.1 6.2 >file2.expect &&
 	test_cmp file1.expect file1 &&
-	test_cmp file2.expect file2
+	test_cmp file2.expect file2 &&
+
+	# Pretend that the resolutions are old again
+	find .git/rr-cache/ -type f | xargs test-chmtime -172800 &&
+
+	# Resolved entries have not expired yet
+	git -c gc.rerereresolved=5 -c gc.rerereunresolved=5 rerere gc &&
+
+	count_pre_post 2 2 &&
+
+	# Resolved entries have expired
+	git -c gc.rerereresolved=1 -c gc.rerereunresolved=5 rerere gc &&
+	count_pre_post 0 0
 '
 
 test_done

diff --git a/rerere.c b/rerere.c
index 3d4dd33..2b870e0 100644
--- a/rerere.c
+++ b/rerere.c
@@ -517,103 +517,6 @@ static int handle_file(const char *path, unsigned char *sha1, const char *output
 }
 
 /*
- * Subclass of rerere_io that reads from an in-core buffer that is a
- * strbuf
- */
-struct rerere_io_mem {
-	struct rerere_io io;
-	struct strbuf input;
-};
-
-/*
- * ... and its getline() method implementation
- */
-static int rerere_mem_getline(struct strbuf *sb, struct rerere_io *io_)
-{
-	struct rerere_io_mem *io = (struct rerere_io_mem *)io_;
-	char *ep;
-	size_t len;
-
-	strbuf_release(sb);
-	if (!io->input.len)
-		return -1;
-	ep = memchr(io->input.buf, '\n', io->input.len);
-	if (!ep)
-		ep = io->input.buf + io->input.len;
-	else if (*ep == '\n')
-		ep++;
-	len = ep - io->input.buf;
-	strbuf_add(sb, io->input.buf, len);
-	strbuf_remove(&io->input, 0, len);
-	return 0;
-}
-
-static int handle_cache(const char *path, unsigned char *sha1, const char *output)
-{
-	mmfile_t mmfile[3] = {{NULL}};
-	mmbuffer_t result = {NULL, 0};
-	const struct cache_entry *ce;
-	int pos, len, i, hunk_no;
-	struct rerere_io_mem io;
-	int marker_size = ll_merge_marker_size(path);
-
-	/*
-	 * Reproduce the conflicted merge in-core
-	 */
-	len = strlen(path);
-	pos = cache_name_pos(path, len);
-	if (0 <= pos)
-		return -1;
-	pos = -pos - 1;
-
-	while (pos < active_nr) {
-		enum object_type type;
-		unsigned long size;
-
-		ce = active_cache[pos++];
-		if (ce_namelen(ce) != len || memcmp(ce->name, path, len))
-			break;
-		i = ce_stage(ce) - 1;
-		if (!mmfile[i].ptr) {
-			mmfile[i].ptr = read_sha1_file(ce->sha1, &type, &size);
-			mmfile[i].size = size;
-		}
-	}
-	for (i = 0; i < 3; i++)
-		if (!mmfile[i].ptr && !mmfile[i].size)
-			mmfile[i].ptr = xstrdup("");
-
-	/*
-	 * NEEDSWORK: handle conflicts from merges with
-	 * merge.renormalize set, too
-	 */
-	ll_merge(&result, path, &mmfile[0], NULL,
-		 &mmfile[1], "ours",
-		 &mmfile[2], "theirs", NULL);
-	for (i = 0; i < 3; i++)
-		free(mmfile[i].ptr);
-
-	memset(&io, 0, sizeof(io));
-	io.io.getline = rerere_mem_getline;
-	if (output)
-		io.io.output = fopen(output, "w");
-	else
-		io.io.output = NULL;
-	strbuf_init(&io.input, 0);
-	strbuf_attach(&io.input, result.ptr, result.size, result.size);
-
-	/*
-	 * Grab the conflict ID and optionally write the original
-	 * contents with conflict markers out.
-	 */
-	hunk_no = handle_path(sha1, (struct rerere_io *)&io, marker_size);
-	strbuf_release(&io.input);
-	if (io.io.output)
-		fclose(io.io.output);
-	return hunk_no;
-}
-
-/*
  * Look at a cache entry at "i" and see if it is not conflicting,
  * conflicting and we are willing to handle, or conflicting and
  * we are unable to handle, and return the determination in *type.
@@ -1005,6 +908,103 @@ int rerere(int flags)
 	return status;
 }
 
+/*
+ * Subclass of rerere_io that reads from an in-core buffer that is a
+ * strbuf
+ */
+struct rerere_io_mem {
+	struct rerere_io io;
+	struct strbuf input;
+};
+
+/*
+ * ... and its getline() method implementation
+ */
+static int rerere_mem_getline(struct strbuf *sb, struct rerere_io *io_)
+{
+	struct rerere_io_mem *io = (struct rerere_io_mem *)io_;
+	char *ep;
+	size_t len;
+
+	strbuf_release(sb);
+	if (!io->input.len)
+		return -1;
+	ep = memchr(io->input.buf, '\n', io->input.len);
+	if (!ep)
+		ep = io->input.buf + io->input.len;
+	else if (*ep == '\n')
+		ep++;
+	len = ep - io->input.buf;
+	strbuf_add(sb, io->input.buf, len);
+	strbuf_remove(&io->input, 0, len);
+	return 0;
+}
+
+static int handle_cache(const char *path, unsigned char *sha1, const char *output)
+{
+	mmfile_t mmfile[3] = {{NULL}};
+	mmbuffer_t result = {NULL, 0};
+	const struct cache_entry *ce;
+	int pos, len, i, hunk_no;
+	struct rerere_io_mem io;
+	int marker_size = ll_merge_marker_size(path);
+
+	/*
+	 * Reproduce the conflicted merge in-core
+	 */
+	len = strlen(path);
+	pos = cache_name_pos(path, len);
+	if (0 <= pos)
+		return -1;
+	pos = -pos - 1;
+
+	while (pos < active_nr) {
+		enum object_type type;
+		unsigned long size;
+
+		ce = active_cache[pos++];
+		if (ce_namelen(ce) != len || memcmp(ce->name, path, len))
+			break;
+		i = ce_stage(ce) - 1;
+		if (!mmfile[i].ptr) {
+			mmfile[i].ptr = read_sha1_file(ce->sha1, &type, &size);
+			mmfile[i].size = size;
+		}
+	}
+	for (i = 0; i < 3; i++)
+		if (!mmfile[i].ptr && !mmfile[i].size)
+			mmfile[i].ptr = xstrdup("");
+
+	/*
+	 * NEEDSWORK: handle conflicts from merges with
+	 * merge.renormalize set, too?
+	 */
+	ll_merge(&result, path, &mmfile[0], NULL,
+		 &mmfile[1], "ours",
+		 &mmfile[2], "theirs", NULL);
+	for (i = 0; i < 3; i++)
+		free(mmfile[i].ptr);
+
+	memset(&io, 0, sizeof(io));
+	io.io.getline = rerere_mem_getline;
+	if (output)
+		io.io.output = fopen(output, "w");
+	else
+		io.io.output = NULL;
+	strbuf_init(&io.input, 0);
+	strbuf_attach(&io.input, result.ptr, result.size, result.size);
+
+	/*
+	 * Grab the conflict ID and optionally write the original
+	 * contents with conflict markers out.
+	 */
+	hunk_no = handle_path(sha1, (struct rerere_io *)&io, marker_size);
+	strbuf_release(&io.input);
+	if (io.io.output)
+		fclose(io.io.output);
+	return hunk_no;
+}
+
 static int rerere_forget_one_path(const char *path, struct string_list *rr)
 {
 	const char *filename;

diff --git a/rerere.c b/rerere.c
index 2b870e0..e636d4b 100644
--- a/rerere.c
+++ b/rerere.c
@@ -622,6 +622,33 @@ int rerere_remaining(struct string_list *merge_rr)
 }
 
 /*
+ * Try using the given conflict resolution "ID" to see
+ * if that recorded conflict resolves cleanly what we
+ * got in the "cur".
+ */
+static int try_merge(const struct rerere_id *id, const char *path,
+		     mmfile_t *cur, mmbuffer_t *result)
+{
+	int ret;
+	mmfile_t base = {NULL, 0}, other = {NULL, 0};
+
+	if (read_mmfile(&base, rerere_path(id, "preimage")) ||
+	    read_mmfile(&other, rerere_path(id, "postimage")))
+		ret = 1;
+	else
+		/*
+		 * A three-way merge. Note that this honors user-customizable
+		 * low-level merge driver settings.
+		 */
+		ret = ll_merge(result, path, &base, NULL, cur, "", &other, "", NULL);
+
+	free(base.ptr);
+	free(other.ptr);
+
+	return ret;
+}
+
+/*
  * Find the conflict identified by "id"; the change between its
  * "preimage" (i.e. a previous contents with conflict markers) and its
  * "postimage" (i.e. the corresponding contents with conflicts
@@ -635,30 +662,20 @@ static int merge(const struct rerere_id *id, const char *path)
 {
 	FILE *f;
 	int ret;
-	mmfile_t cur = {NULL, 0}, base = {NULL, 0}, other = {NULL, 0};
+	mmfile_t cur = {NULL, 0};
 	mmbuffer_t result = {NULL, 0};
 
 	/*
 	 * Normalize the conflicts in path and write it out to
 	 * "thisimage" temporary file.
 	 */
-	if (handle_file(path, NULL, rerere_path(id, "thisimage")) < 0) {
-		ret = 1;
-		goto out;
-	}
-
-	if (read_mmfile(&cur, rerere_path(id, "thisimage")) ||
-	    read_mmfile(&base, rerere_path(id, "preimage")) ||
-	    read_mmfile(&other, rerere_path(id, "postimage"))) {
+	if ((handle_file(path, NULL, rerere_path(id, "thisimage")) < 0) ||
+	    read_mmfile(&cur, rerere_path(id, "thisimage"))) {
 		ret = 1;
 		goto out;
 	}
 
-	/*
-	 * A three-way merge. Note that this honors user-customizable
-	 * low-level merge driver settings.
-	 */
-	ret = ll_merge(&result, path, &base, NULL, &cur, "", &other, "", NULL);
+	ret = try_merge(id, path, &cur, &result);
 	if (ret)
 		goto out;
 
@@ -684,8 +701,6 @@ static int merge(const struct rerere_id *id, const char *path)
 
 out:
 	free(cur.ptr);
-	free(base.ptr);
-	free(other.ptr);
 	free(result.ptr);
 
 	return ret;

rerere.c, t/t4200-rerere.sh

diff --git a/rerere.c b/rerere.c
index e636d4b..1693866 100644
--- a/rerere.c
+++ b/rerere.c
@@ -1038,7 +1038,33 @@ static int rerere_forget_one_path(const char *path, struct string_list *rr)
 
 	/* Nuke the recorded resolution for the conflict */
 	id = new_rerere_id(sha1);
-	id->variant = 0; /* for now */
+
+	for (id->variant = 0;
+	     id->variant < id->collection->status_nr;
+	     id->variant++) {
+		mmfile_t cur = { NULL, 0 };
+		mmbuffer_t result = {NULL, 0};
+		int cleanly_resolved;
+
+		if (!has_rerere_resolution(id))
+			continue;
+
+		handle_cache(path, sha1, rerere_path(id, "thisimage"));
+		if (read_mmfile(&cur, rerere_path(id, "thisimage"))) {
+			free(cur.ptr);
+			return error("Failed to update conflicted state in '%s'",
+				     path);
+		}
+		cleanly_resolved = !try_merge(id, path, &cur, &result);
+		free(result.ptr);
+		free(cur.ptr);
+		if (cleanly_resolved)
+			break;
+	}
+
+	if (id->collection->status_nr <= id->variant)
+		return error("no remembered resolution for '%s'", path);
+
 	filename = rerere_path(id, "postimage");
 	if (unlink(filename))
 		return (errno == ENOENT
diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index a85fc7d..1a080e7 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -536,6 +536,16 @@ test_expect_success 'multiple identical conflicts' '
 	test_cmp file1.expect file1 &&
 	test_cmp file2.expect file2 &&
 
+	# Forget resolution for file2
+	git rerere forget file2 &&
+	echo file2 >expect &&
+	git rerere status >actual &&
+	test_cmp expect actual &&
+	count_pre_post 2 1 &&
+
+	# file2 already has correct resolution, so record it again
+	git rerere &&
+
 	# Pretend that the resolutions are old again
 	find .git/rr-cache/ -type f | xargs test-chmtime -172800 &&