[PATCH 2/3] commit.c: make compare_commits_by_commit_date global

[Jeff King <peff@peff.net>]

This helper function was introduced as a prio_queue
comparator to help topological sorting. However, other users
of prio_queue who want to replace commit_list_insert_by_date
will want to use it, too. So let's make it public.

Signed-off-by: Jeff King <peff@peff.net>
---
There is also compare_commits_by_author_date, but I expect it to be less
generally useful (especially because it relies on a slab), so I didn't
bother publicizing it.  I think this is sufficient for now, and any
later users can make the author version public if they need to.

Note also that we have a similar comparison function,
commit_list_compare_by_date, which gets fed to the linked-list mergesort
for commit_list_sort_by_date. I was tempted to unify them, but we can't,
because it takes an actual "struct commit_list *", not a "struct commit
*" (and the logic is not so complex that it is worth factoring out to a
shared helper).

 commit.c | 2 +-
 commit.h | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/commit.c b/commit.c
index 521e49c..ebc0eea 100644
--- a/commit.c
+++ b/commit.c
@@ -581,7 +581,7 @@ static int compare_commits_by_author_date(const void *a_, const void *b_,
 	return 0;
 }
 
-static int compare_commits_by_commit_date(const void *a_, const void *b_, void *unused)
+int compare_commits_by_commit_date(const void *a_, const void *b_, void *unused)
 {
 	const struct commit *a = a_, *b = b_;
 	/* newer commits with larger date first */
diff --git a/commit.h b/commit.h
index 4d452dc..18a5234 100644
--- a/commit.h
+++ b/commit.h
@@ -254,4 +254,6 @@ extern void check_commit_signature(const struct commit* commit, struct signature
  */
 extern void check_commit_signature(const struct commit* commit, struct signature_check *sigc);
 
+int compare_commits_by_commit_date(const void *a_, const void *b_, void *unused);
+
 #endif /* COMMIT_H */
-- 
1.8.3.rc2.14.g7eee6b3