Fix status for files under ignored dirs

There was a bug where tracked files inside directories that were
inside ignored directories where not being found by status.  To
make that a little clearer, if you have a .gitignore with:

    ignore/

And then have the following files:

    ignore/dir/tracked     <-- actually a tracked file
    ignore/dir/untracked   <-- should be ignored

Then we would show the tracked file as being removed (because
when we got the to contained item "dir/" inside the ignored
directory, we decided it was safe to skip -- bzzt, wrong!).

This update is much more careful about checking that we are
not skipping over any prefix of a tracked item, regardless of
whether it is ignored or not.

As documented in diff.c, this commit does create behavior that
still differs from core git with regards to the handling of
untracked files contained inside ignored directories.  With
libgit2, those files will just not show up in status or diff.
With core git, those files don't show up in status or diff
either *unless* they are explicitly ignored by a .gitignore
pattern in which case they show up as ignored files.

Needless to say, this is a local behavior difference only, so
it should not be important and (to me) the libgit2 behavior
seems more consistent.

1 files changed, 40 insertions, 20 deletions

diff --git a/src/diff.c b/src/diff.c
index c8670b53e..d5c0c8ba5 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -551,29 +551,27 @@ static int diff_from_iterators(
 		 * matched in old (and/or descend into directories as needed)
 		 */
 		else if (nitem && (!oitem || strcmp(oitem->path, nitem->path) > 0)) {
-			int is_ignored;
-			git_delta_t delta_type = GIT_DELTA_ADDED;
+			git_delta_t delta_type = GIT_DELTA_UNTRACKED;
 
-			/* contained in ignored parent directory, so this can be skipped. */
+			/* check if contained in ignored parent directory */
 			if (git_buf_len(&ignore_prefix) &&
 				git__prefixcmp(nitem->path, git_buf_cstr(&ignore_prefix)) == 0)
-			{
-				if (git_iterator_advance(new_iter, &nitem) < 0)
-					goto fail;
-
-				continue;
-			}
-
-			is_ignored = git_iterator_current_is_ignored(new_iter);
+				delta_type = GIT_DELTA_IGNORED;
 
 			if (S_ISDIR(nitem->mode)) {
-				/* recurse into directory if explicitly requested or
-				 * if there are tracked items inside the directory
+				/* recurse into directory only if there are tracked items in
+				 * it or if the user requested the contents of untracked
+				 * directories and it is not under an ignored directory.
 				 */
-				if ((diff->opts.flags & GIT_DIFF_RECURSE_UNTRACKED_DIRS) ||
-					(oitem && git__prefixcmp(oitem->path, nitem->path) == 0))
+				if ((oitem && git__prefixcmp(oitem->path, nitem->path) == 0) ||
+					(delta_type == GIT_DELTA_UNTRACKED &&
+					 (diff->opts.flags & GIT_DIFF_RECURSE_UNTRACKED_DIRS) != 0))
 				{
-					if (is_ignored)
+					/* if this directory is ignored, remember it as the
+					 * "ignore_prefix" for processing contained items
+					 */
+					if (delta_type == GIT_DELTA_UNTRACKED &&
+						git_iterator_current_is_ignored(new_iter))
 						git_buf_sets(&ignore_prefix, nitem->path);
 
 					if (git_iterator_advance_into_directory(new_iter, &nitem) < 0)
@@ -581,12 +579,34 @@ static int diff_from_iterators(
 
 					continue;
 				}
-				delta_type = GIT_DELTA_UNTRACKED;
 			}
-			else if (is_ignored)
+
+			/* In core git, the next two "else if" clauses are effectively
+			 * reversed -- i.e. when an untracked file contained in an
+			 * ignored directory is individually ignored, it shows up as an
+			 * ignored file in the diff list, even though other untracked
+			 * files in the same directory are skipped completely.
+			 *
+			 * To me, this is odd.  If the directory is ignored and the file
+			 * is untracked, we should skip it consistently, regardless of
+			 * whether it happens to match a pattern in the ignore file.
+			 *
+			 * To match the core git behavior, just reverse the following
+			 * two "else if" cases so that individual file ignores are
+			 * checked before container directory exclusions are used to
+			 * skip the file.
+			 */
+			else if (delta_type == GIT_DELTA_IGNORED) {
+				if (git_iterator_advance(new_iter, &nitem) < 0)
+					goto fail;
+				continue; /* ignored parent directory, so skip completely */
+			}
+
+			else if (git_iterator_current_is_ignored(new_iter))
 				delta_type = GIT_DELTA_IGNORED;
-			else if (new_iter->type == GIT_ITERATOR_WORKDIR)
-				delta_type = GIT_DELTA_UNTRACKED;
+
+			else if (new_iter->type != GIT_ITERATOR_WORKDIR)
+				delta_type = GIT_DELTA_ADDED;
 
 			if (diff_delta__from_one(diff, delta_type, nitem) < 0 ||
 				git_iterator_advance(new_iter, &nitem) < 0)