commit-reach(repo_in_merge_bases_many): report missing commits

Some functions in Git's source code follow the convention that returning
a negative value indicates a fatal error, e.g. repository corruption.

Let's use this convention in `repo_in_merge_bases()` to report when one
of the specified commits is missing (i.e. when `repo_parse_commit()`
reports an error).

Also adjust the callers of `repo_in_merge_bases()` to handle such
negative return values.

Note: As of this patch, errors are returned only if any of the specified
merge heads is missing. Over the course of the next patches, missing
commits will also be reported by the `paint_down_to_common()` function,
which is called by `repo_in_merge_bases_many()`, and those errors will
be properly propagated back to the caller at that stage.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/builtin/merge-base.c b/builtin/merge-base.c
index d26e8fbf6f..b0b3838d5f 100644
--- a/builtin/merge-base.c
+++ b/builtin/merge-base.c
@@ -100,12 +100,16 @@ static int handle_octopus(int count, const char **args, int show_all)
 static int handle_is_ancestor(int argc, const char **argv)
 {
 	struct commit *one, *two;
+	int ret;
 
 	if (argc != 2)
 		die("--is-ancestor takes exactly two commits");
 	one = get_commit_reference(argv[0]);
 	two = get_commit_reference(argv[1]);
-	if (repo_in_merge_bases(the_repository, one, two))
+	ret = repo_in_merge_bases(the_repository, one, two);
+	if (ret < 0)
+		exit(128);
+	if (ret)
 		return 0;
 	else
 		return 1;