[PATCH] Add 'git show-branch'.

The 'git show-branches' command turns out to be reasonably useful,
but painfully slow.  So rewrite it in C, using ideas from merge-base
while enhancing it a bit more.

 - Unlike show-branches, it can take --heads (show me all my
   heads), --tags (show me all my tags), or --all (both).

 - It can take --more=<number> to show beyond the merge-base.

 - It shows the short name for each commit in the extended SHA1
   syntax.

 - It can find merge-base for more than two heads.

Examples:

    $ git show-branch --more=6 HEAD

    is almost the same as "git log --pretty=oneline --max-count=6".

    $ git show-branch --merge-base master mhf misc

    finds the merge base of the three given heads.

    $ git show-branch master mhf misc

    shows logs from the top of these three branch heads, up to their
    common ancestor commit is shown.

    $ git show-branch --all --more=10

    is poor-man's gitk, showing all the tags and heads, and
    going back 10 commits beyond the merge base of those refs.

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 15 insertions, 6 deletions

diff --git a/commit.c b/commit.c
index 59e93d4590..e51eda1524 100644
--- a/commit.c
+++ b/commit.c
@@ -38,23 +38,32 @@ enum cmit_fmt get_commit_format(const char *arg)
 	die("invalid --pretty format");
 }
 
-static struct commit *check_commit(struct object *obj, const unsigned char *sha1)
+static struct commit *check_commit(struct object *obj,
+				   const unsigned char *sha1,
+				   int quiet)
 {
 	if (obj->type != commit_type) {
-		error("Object %s is a %s, not a commit", 
-		      sha1_to_hex(sha1), obj->type);
+		if (!quiet)
+			error("Object %s is a %s, not a commit",
+			      sha1_to_hex(sha1), obj->type);
 		return NULL;
 	}
 	return (struct commit *) obj;
 }
 
-struct commit *lookup_commit_reference(const unsigned char *sha1)
+struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
+					      int quiet)
 {
 	struct object *obj = deref_tag(parse_object(sha1));
 
 	if (!obj)
 		return NULL;
-	return check_commit(obj, sha1);
+	return check_commit(obj, sha1, quiet);
+}
+
+struct commit *lookup_commit_reference(const unsigned char *sha1)
+{
+	return lookup_commit_reference_gently(sha1, 0);
 }
 
 struct commit *lookup_commit(const unsigned char *sha1)
@@ -69,7 +78,7 @@ struct commit *lookup_commit(const unsigned char *sha1)
 	}
 	if (!obj->type)
 		obj->type = commit_type;
-	return check_commit(obj, sha1);
+	return check_commit(obj, sha1, 0);
 }
 
 static unsigned long parse_commit_date(const char *buf)