git-range-diff ignoring commit message changes

From: Gwyneth Morgan <gwymor@tilde.club>
Date: Jan 15, 2024, 19:40 UTC
Message-ID: <ZaWKNI5qLPf4P75A@tilde.club>

Is there a way to make git-range-diff to ignore commit messages when considering if commits are identical? When range-diffing long series there are cases where I would like to check at a glance whether the code has changed, and only when the code has changed do I want to see the change in commit message too.

It seems I can approximate what I want by tweaking range-diff's source like this but I couldn't tell if there was an actual option:

diff --git a/range-diff.c b/range-diff.c
index c45b6d849c..fd421b7b99 100644
--- a/range-diff.c
+++ b/range-diff.c
@@ -59,7 +59,7 @@ static int read_patches(const char *range, struct string_list *list,
 		     "--output-indicator-old=<",
 		     "--output-indicator-context=#",
 		     "--no-abbrev-commit",
-		     "--pretty=medium",
+		     "--pretty=format:commit %H",
 		     "--show-notes-by-default",
 		     NULL);
 	strvec_push(&cp.args, range);

This ignores commit message changes entirely, but it would be nice to
have an option to only see commit message changes when the code diff has
changed. It would also be convenient to have a way to only consider
changes in the title of commits but ignore the message body (equivalent
to "--pretty=short" above).

You could get some of this information with git-cherry, but that is
suited for different uses (only cares about new commits on one side,
doesn't show diffs) and would take more effort than just ignoring the
commit messages in the current range-diff output.