diff: skip implicit no-index check when given --no-index

We can invoke no-index mode in two ways: by an explicit
request from the user, or implicitly by noticing that we
have two paths, and at least one is outside the repository.

If the user already told us --no-index, there is no need for
us to do the implicit test at all.  However, we currently
do, and downgrade our "explicit" to DIFF_NO_INDEX_IMPLICIT.

This doesn't have any user-visible behavior, though it's not
immediately obvious why. We only trigger the implicit check
when we have exactly two non-option arguments. And the only
code that cares about implicit versus explicit is an error
message that we show when we _don't_ have two non-option
arguments.

However, it's worth fixing anyway. Besides being slightly
more efficient, it makes the code easier to follow, which
will help when we modify it in future patches.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 13 insertions, 12 deletions

diff --git a/builtin/diff.c b/builtin/diff.c
index d6b8f9834d..7b2a7448ed 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -301,20 +301,21 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 			break;
 	}
 
-	if (!no_index)
+	if (!no_index) {
 		prefix = setup_git_directory_gently(&nongit);
 
-	/*
-	 * Treat git diff with at least one path outside of the
-	 * repo the same as if the command would have been executed
-	 * outside of a git repository.  In this case it behaves
-	 * the same way as "git diff --no-index <a> <b>", which acts
-	 * as a colourful "diff" replacement.
-	 */
-	if (nongit || ((argc == i + 2) &&
-		       (!path_inside_repo(prefix, argv[i]) ||
-			!path_inside_repo(prefix, argv[i + 1]))))
-		no_index = DIFF_NO_INDEX_IMPLICIT;
+		/*
+		 * Treat git diff with at least one path outside of the
+		 * repo the same as if the command would have been executed
+		 * outside of a git repository.  In this case it behaves
+		 * the same way as "git diff --no-index <a> <b>", which acts
+		 * as a colourful "diff" replacement.
+		 */
+		if (nongit || ((argc == i + 2) &&
+			       (!path_inside_repo(prefix, argv[i]) ||
+				!path_inside_repo(prefix, argv[i + 1]))))
+			no_index = DIFF_NO_INDEX_IMPLICIT;
+	}
 
 	if (!no_index)
 		gitmodules_config();