git-diff A...B to (usually) mean "git-diff `git-merge-base A B` B"

This tweaks the argument parser of "git diff" to allow "git-diff
A...B" to show diffs leading to B since their merge-base, when
there is only one sensible merge base between A and B.

Currently nonsense cases are thrown at combined-diff to produce
nonsense results, which would eventually need to be fixed.

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

diff --git a/builtin-diff.c b/builtin-diff.c
index cb38f44..efd3152 100644 (file)
--- a/builtin-diff.c
+++ b/builtin-diff.c
@@ -346,7 +346,15 @@ int cmd_diff(int argc, const char **argv, char **envp)
                return builtin_diff_index(&rev, argc, argv);
        else if (ents == 2)
                return builtin_diff_tree(&rev, argc, argv, ent);
+       else if ((ents == 3) && (ent[0].item->flags & UNINTERESTING)) {
+               /* diff A...B where there is one sane merge base between
+                * A and B.  We have ent[0] == merge-base, ent[1] == A,
+                * and ent[2] == B.  Show diff between the base and B.
+                */
+               return builtin_diff_tree(&rev, argc, argv, ent);
+       }
        else
-               return builtin_diff_combined(&rev, argc, argv, ent, ents);
+               return builtin_diff_combined(&rev, argc, argv,
+                                            ent, ents);
        usage(builtin_diff_usage);
 }