diff: check pathspec on non-files

When we're not doing pathspec matching, we let the iterator handle
file matching for us.  However, we can only trust the iterator to
return *files* that match the pattern, because the iterator must
return directories that are not strictly in the pathlist, but that
are the parents of files that match the pattern, so that diff can
later recurse into them.

Thus, diff must examine non-files explicitly before including them
in the delta list.

src/diff.c

@@ -75,18 +75,27 @@ static int diff_insert_delta(
 }
 
 static bool diff_pathspec_match(
-	const char **matched_pathspec, git_diff *diff, const char *path)
+	const char **matched_pathspec,
+	git_diff *diff,
+	const git_index_entry *entry)
 {
-	/* The iterator has filtered out paths for us, so the fact that we're
-	 * seeing this patch means that it must match the given path list.
+	bool disable_pathspec_match = 
+		DIFF_FLAG_IS_SET(diff, GIT_DIFF_DISABLE_PATHSPEC_MATCH);
+
+	/* If we're disabling fnmatch, then the iterator has already applied
+	 * the filters to the files for us and we don't have to do anything.
+	 * However, this only applies to *files* - the iterator will include
+	 * directories that we need to recurse into when not autoexpanding,
+	 * so we still need to apply the pathspec match to directories.
 	 */
-	if (DIFF_FLAG_IS_SET(diff, GIT_DIFF_DISABLE_PATHSPEC_MATCH)) {
-		*matched_pathspec = path;
+	if ((S_ISLNK(entry->mode) || S_ISREG(entry->mode)) &&
+		disable_pathspec_match) {
+		*matched_pathspec = entry->path;
 		return true;
 	}
 
 	return git_pathspec__match(
-		&diff->pathspec, path, false,
+		&diff->pathspec, entry->path, disable_pathspec_match,
 		DIFF_FLAG_IS_SET(diff, GIT_DIFF_IGNORE_CASE),
 		matched_pathspec, NULL);
 }
@@ -127,7 +136,7 @@ static int diff_delta__from_one(
 		DIFF_FLAG_ISNT_SET(diff, GIT_DIFF_INCLUDE_UNREADABLE))
 		return 0;
 
-	if (!diff_pathspec_match(&matched_pathspec, diff, entry->path))
+	if (!diff_pathspec_match(&matched_pathspec, diff, entry))
 		return 0;
 
 	delta = diff_delta__alloc(diff, status, entry->path);
@@ -768,7 +777,7 @@ static int maybe_modified(
 	const char *matched_pathspec;
 	int error = 0;
 
-	if (!diff_pathspec_match(&matched_pathspec, diff, oitem->path))
+	if (!diff_pathspec_match(&matched_pathspec, diff, oitem))
 		return 0;
 
 	memset(&noid, 0, sizeof(noid));