Re: Git blame only current branch

From: Jeff King <peff@peff.net>
Date: Dec 12, 2011, 16:55 UTC
Message-ID: <20111212165542.GA4802@sigill.intra.peff.net>
In-Reply-To: <d615954f-bed8-482d-a2e3-e1e741d6dd23@mail>

On Mon, Dec 12, 2011 at 10:24:47AM -0500, Stephen Bash wrote:

> I'm curious if there's a method to make git blame merge commits that
> introduce code to the given branch rather than commits on the original
> (topic) branch?  For example:

Usually when you are interested in seeing merges like this in git-log, you would use one of "--first-parent" or "--merges". However, though "git blame" takes revision arguments, it does its own traversal of the graph that does not respect those options.

Modifying it to do --first-parent is pretty easy:

diff --git a/builtin/blame.c b/builtin/blame.c
index 80febbe..c19a8cd 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -1191,6 +1191,8 @@ static int num_scapegoats(struct rev_info *revs, struct commit *commit)
 {
 	int cnt;
 	struct commit_list *l = first_scapegoat(revs, commit);
+	if (revs->first_parent_only)
+		return l ? 1 : 0;
 	for (cnt = 0; l; l = l->next)
 		cnt++;
 	return cnt;

With that, "git blame --first-parent" produces reasonable results for
me. But of course I didn't do more than 30 seconds of testing, so it is
entirely possible there are corner cases or unforeseen side effects.

Handling --merges is probably a little trickier, as you need to consider
only some commits as scapegoats, but still traverse through everything
to find the merges.

-Peff