revision: optionally record matches with pathspec elements

Unlike "git add" and other end-user facing commands, where it is
diagnosed as an error to give a pathspec with an element that does
not match any path, the diff machinery does not care if some
elements of the pathspec do not match.  Given that the diff
machinery is heavily used in pathspec-limited "git log" machinery,
and it is common for a path to come and go while traversing the
project history, this is usually a good thing.

However, in some cases we would want to know if all the pathspec
elements matched.  For example, "git add -u <pathspec>" internally
uses the machinery used by "git diff-files" to decide contents from
what paths to add to the index, and as an end-user facing command,
"git add -u" would want to report an unmatched pathspec element.

Add a new .ps_matched member next to the .prune_data member in
"struct rev_info" so that we can optionally keep track of the use of
.prune_data pathspec elements that can be inspected by the caller.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/diff-lib.c b/diff-lib.c
index 1cd790a4d2..683f11e509 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -127,7 +127,16 @@ void run_diff_files(struct rev_info *revs, unsigned int option)
 		if (diff_can_quit_early(&revs->diffopt))
 			break;
 
-		if (!ce_path_match(istate, ce, &revs->prune_data, NULL))
+		/*
+		 * NEEDSWORK:
+		 * Here we filter with pathspec but the result is further
+		 * filtered out when --relative is in effect.  To end-users,
+		 * a pathspec element that matched only to paths outside the
+		 * current directory is like not matching anything at all;
+		 * the handling of ps_matched[] here may become problematic
+		 * if/when we add the "--error-unmatch" option to "git diff".
+		 */
+		if (!ce_path_match(istate, ce, &revs->prune_data, revs->ps_matched))
 			continue;
 
 		if (revs->diffopt.prefix &&