Re: My git repo is broken, how to fix it ?

From

Junio C Hamano <junkio@cox.net>

Date

Mar 20, 2007, 07:42 UTC

Message-ID

<7vd5349x97.fsf@assigned-by-dhcp.cox.net>

In-Reply-To

<Pine.LNX.4.64.0703192212280.6730@woody.linux-foundation.org>

Linus Torvalds <torvalds@linux-foundation.org> writes:

> But to really look at this we should probably add a "really_careful" flag 
> that actually re-verifies the SHA1 on read so that we'd catch these kinds 
> of corruptions early. 
> ...
> I'm hoping somebody has any ideas. We really *could* check the SHA1 on 
> each read (and slow down git a lot) and that would catch corruption much 
> faster and hopefully pinpoint it more quickly where exactly it happens. 

diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
index 73d448b..5d0692a 100644
--- a/builtin-pack-objects.c
+++ b/builtin-pack-objects.c
@@ -65,6 +65,7 @@ static int no_reuse_delta;
 static int local;
 static int incremental;
 static int allow_ofs_delta;
+static int revalidate_sha1;
 
 static struct object_entry **sorted_by_sha, **sorted_by_type;
 static struct object_entry *objects;
@@ -974,8 +975,31 @@ static void add_preferred_base(unsigned char *sha1)
 	it->pcache.tree_size = size;
 }
 
-static void check_object(struct object_entry *entry)
+static void check_object(struct object_entry *entry, int ith, unsigned *last)
 {
+	if (revalidate_sha1) {
+		unsigned char sha1[20];
+		enum object_type type;
+		unsigned long size;
+		void *buf;
+
+		buf = read_sha1_file(entry->sha1, &type, &size);
+		hash_sha1_file(buf, size, typename(type), sha1);
+		if (hashcmp(sha1, entry->sha1))
+			die("'%s': hash mismatch", sha1_to_hex(entry->sha1));
+		free(buf);
+
+		if (progress) {
+			unsigned percent = ith * 100 / nr_objects;
+			if (percent != *last || progress_update) {
+				fprintf(stderr, "%4u%% (%u/%u) done\r",
+					percent, ith, nr_objects);
+				progress_update = 0;
+				*last = percent;
+			}
+		}
+	}
+
 	if (entry->in_pack && !entry->preferred_base) {
 		struct packed_git *p = entry->in_pack;
 		struct pack_window *w_curs = NULL;
@@ -1082,10 +1106,16 @@ static void get_object_details(void)
 {
 	uint32_t i;
 	struct object_entry *entry;
+	unsigned last_percent = 999;
+
+	if (progress && revalidate_sha1)
+		fprintf(stderr, "Revalidating %u objects.\n", nr_objects);
 
 	prepare_pack_ix();
 	for (i = 0, entry = objects; i < nr_objects; i++, entry++)
-		check_object(entry);
+		check_object(entry, i+1, &last_percent);
+	if (progress && revalidate_sha1)
+		fputc('\n', stderr);
 
 	if (nr_objects == nr_result) {
 		/*
@@ -1629,6 +1659,10 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 			rp_av[1] = "--objects-edge";
 			continue;
 		}
+		if (!strcmp("--revalidate", arg)) {
+			revalidate_sha1 = 1;
+			continue;
+		}
 		usage(pack_usage);
 	}