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[PATCH 11/13] Introduce reduce_heads()

From
Miklos Vajna <vmiklos@frugalware.org>
Date
Jun 21, 2008, 17:00 UTC
Message-ID
<5cae08d3bf2852a8bbd8dc8cdf741cb4bdfa237e.1214066799.git.vmiklos@frugalware.org>
In-Reply-To
<57d8a308fae0012174ed4388baccf1bde8515f2f.1214066799.git.vmiklos@frugalware.org>
From: Junio C Hamano <gitster@pobox.com>

The new function reduce_heads() is given a list of commits, and removes ones that can be reached from other commits in the list. It is useful for reducing the commits randomly thrown at the git-merge command and remove redundant commits that the user shouldn't have given to it.

The implementation uses the get_merge_bases_many() introduced in the previous commit. If the merge base between one commit taken from the list and the remaining commits is the commit itself, that means the commit is reachable from some of the other commits.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Makefile               |    1 +
 builtin-reduce-heads.c |   44 ++++++++++++++++++++++++++++++++++++++++++++
 builtin.h              |    1 +
 commit.c               |   45 +++++++++++++++++++++++++++++++++++++++++++++
 commit.h               |    2 ++
 git.c                  |    1 +
 6 files changed, 94 insertions(+), 0 deletions(-)
 create mode 100644 builtin-reduce-heads.c
diff --git a/Makefile b/Makefile
index b003e3e..d660756 100644
--- a/Makefile
+++ b/Makefile
@@ -522,6 +522,7 @@ BUILTIN_OBJS += builtin-pack-refs.o
 BUILTIN_OBJS += builtin-prune-packed.o
 BUILTIN_OBJS += builtin-prune.o
 BUILTIN_OBJS += builtin-push.o
+BUILTIN_OBJS += builtin-reduce-heads.o
 BUILTIN_OBJS += builtin-read-tree.o
 BUILTIN_OBJS += builtin-reflog.o
 BUILTIN_OBJS += builtin-remote.o
diff --git a/builtin-reduce-heads.c b/builtin-reduce-heads.c
new file mode 100644
index 0000000..ff6178d
--- /dev/null
+++ b/builtin-reduce-heads.c
@@ -0,0 +1,44 @@
+#include "cache.h"
+#include "commit.h"
+#include "strbuf.h"
+
+static void show_commit_list(struct commit_list *list)
+{
+	while (list) {
+		struct strbuf it;
+		struct commit *commit = list->item;
+
+		list = list->next;
+		strbuf_init(&it, 128);
+		parse_commit(commit);
+		pretty_print_commit(CMIT_FMT_ONELINE, commit, &it,
+				    0, NULL, NULL, 0, 0);
+		puts(it.buf);
+		strbuf_release(&it);
+	}
+}
+
+int cmd_reduce_heads(int ac, const char **av, const char *prefix)
+{
+	struct commit_list *list = NULL, **tail = &list;
+	int i;
+
+	for (i = 1; i < ac; i++) {
+		struct commit *commit;
+		unsigned char sha1[20];
+
+		if (get_sha1(av[i], sha1))
+			die("'%s' is not a valid ref.", av[i]);
+		commit = lookup_commit_reference(sha1);
+		if (!commit)
+			die("cannot find commit %s", av[i]);
+		tail = &commit_list_insert(commit, tail)->next;
+	}
+
+	show_commit_list(list);
+	putchar('\n');
+
+	list = reduce_heads(list);
+	show_commit_list(list);
+	return 0;
+}
diff --git a/builtin.h b/builtin.h
index 2b01fea..f069ee7 100644
--- a/builtin.h
+++ b/builtin.h
@@ -75,6 +75,7 @@ extern int cmd_read_tree(int argc, const char **argv, const char *prefix);
 extern int cmd_reflog(int argc, const char **argv, const char *prefix);
 extern int cmd_remote(int argc, const char **argv, const char *prefix);
 extern int cmd_config(int argc, const char **argv, const char *prefix);
+extern int cmd_reduce_heads(int argc, const char **argv, const char *prefix);
 extern int cmd_rerere(int argc, const char **argv, const char *prefix);
 extern int cmd_reset(int argc, const char **argv, const char *prefix);
 extern int cmd_rev_list(int argc, const char **argv, const char *prefix);
diff --git a/commit.c b/commit.c
index cafed26..d20b14e 100644
--- a/commit.c
+++ b/commit.c
@@ -725,3 +725,48 @@ int in_merge_bases(struct commit *commit, struct commit **reference, int num)
 	free_commit_list(bases);
 	return ret;
 }
+
+struct commit_list *reduce_heads(struct commit_list *heads)
+{
+	struct commit_list *p;
+	struct commit_list *result = NULL, **tail = &result;
+	struct commit **other;
+	size_t num_head, num_other;
+
+	if (!heads)
+		return NULL;
+
+	/* Avoid unnecessary reallocations */
+	for (p = heads, num_head = 0; p; p = p->next)
+		num_head++;
+	other = xcalloc(sizeof(*other), num_head);
+
+	/* For each commit, see if it can be reached by others */
+	for (p = heads; p; p = p->next) {
+		struct commit_list *q, *base;
+
+		num_other = 0;
+		for (q = heads; q; q = q->next) {
+			if (p == q)
+				continue;
+			other[num_other++] = q->item;
+		}
+		if (num_other) {
+			base = get_merge_bases_many(p->item, num_other, other, 1);
+		} else
+			base = NULL;
+		/*
+		 * If p->item does not have anything common with other
+		 * commits, there won't be any merge base.  If it is
+		 * reachable from some of the others, p->item will be
+		 * the merge base.  If its history is connected with
+		 * others, but p->item is not reachable by others, we
+		 * will get something other than p->item back.
+		 */
+		if (!base || (base->item != p->item))
+			tail = &(commit_list_insert(p->item, tail)->next);
+		free_commit_list(base);
+	}
+	free(other);
+	return result;
+}
diff --git a/commit.h b/commit.h
index dcec7fb..2acfc79 100644
--- a/commit.h
+++ b/commit.h
@@ -140,4 +140,6 @@ static inline int single_parent(struct commit *commit)
 	return commit->parents && !commit->parents->next;
 }
 
+struct commit_list *reduce_heads(struct commit_list *heads);
+
 #endif /* COMMIT_H */
diff --git a/git.c b/git.c
index 2fbe96b..80b16ce 100644
--- a/git.c
+++ b/git.c
@@ -285,6 +285,7 @@ static void handle_internal_command(int argc, const char **argv)
 		{ "prune-packed", cmd_prune_packed, RUN_SETUP },
 		{ "push", cmd_push, RUN_SETUP },
 		{ "read-tree", cmd_read_tree, RUN_SETUP },
+		{ "reduce-heads", cmd_reduce_heads, RUN_SETUP },
 		{ "reflog", cmd_reflog, RUN_SETUP },
 		{ "remote", cmd_remote, RUN_SETUP },
 		{ "repo-config", cmd_config },

-- 
1.5.6
Previous: Miklos VajnaNext: Miklos Vajna
Message 4 of 15 in “Build in merge”
  1. 00/13 Build in mergeMiklos Vajna, Jun 21, 2008
  2. 09/13 Add new test to ensure git-merge handles more than 25 refs.Miklos Vajna, Jun 21, 2008
  3. 10/13 Introduce get_merge_bases_many()Miklos Vajna, Jun 21, 2008
  4. 11/13 Introduce reduce_heads()Miklos Vajna, Jun 21, 2008
  5. 12/13 Build in mergeMiklos Vajna, Jun 21, 2008
  6. 13/13 Add new test case to ensure git-merge filters for independent parentsMiklos Vajna, Jun 21, 2008
  7. 13/13 Add new test case to ensure git-merge reduces octopus parents when possibleMiklos Vajna, Jun 21, 2008
  8. Olivier MarinJun 25, 2008
  9. Miklos VajnaJun 27, 2008
  10. Olivier MarinJun 27, 2008
  11. Miklos VajnaJun 27, 2008
  12. Olivier MarinJun 27, 2008
  13. Miklos VajnaJun 27, 2008
  14. Johannes SchindelinJun 27, 2008
  15. Miklos VajnaJun 27, 2008

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