1 files changed, 17 insertions, 6 deletions
diff --git a/diff.c b/diff.c
index 7d03419880..534c12e28e 100644
--- a/diff.c
+++ b/diff.c
@@ -2683,6 +2683,13 @@ static int reuse_worktree_file(const char *name, const unsigned char *sha1, int
 	if (!FAST_WORKING_DIRECTORY && !want_file && has_sha1_pack(sha1))
 		return 0;
 
+	/*
+	 * Similarly, if we'd have to convert the file contents anyway, that
+	 * makes the optimization not worthwhile.
+	 */
+	if (!want_file && would_convert_to_git(name))
+		return 0;
+
 	len = strlen(name);
 	pos = cache_name_pos(name, len);
 	if (pos < 0)
@@ -4455,7 +4462,7 @@ static void patch_id_consume(void *priv, char *line, unsigned long len)
 }
 
 /* returns 0 upon success, and writes result into sha1 */
-static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1)
+static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1, int diff_header_only)
 {
 	struct diff_queue_struct *q = &diff_queued_diff;
 	int i;
@@ -4490,9 +4497,6 @@ static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1)
 
 		diff_fill_sha1_info(p->one);
 		diff_fill_sha1_info(p->two);
-		if (fill_mmfile(&mf1, p->one) < 0 ||
-				fill_mmfile(&mf2, p->two) < 0)
-			return error("unable to read files to diff");
 
 		len1 = remove_space(p->one->path, strlen(p->one->path));
 		len2 = remove_space(p->two->path, strlen(p->two->path));
@@ -4527,6 +4531,13 @@ static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1)
 					len2, p->two->path);
 		git_SHA1_Update(&ctx, buffer, len1);
 
+		if (diff_header_only)
+			continue;
+
+		if (fill_mmfile(&mf1, p->one) < 0 ||
+		    fill_mmfile(&mf2, p->two) < 0)
+			return error("unable to read files to diff");
+
 		if (diff_filespec_is_binary(p->one) ||
 		    diff_filespec_is_binary(p->two)) {
 			git_SHA1_Update(&ctx, oid_to_hex(&p->one->oid),
@@ -4549,11 +4560,11 @@ static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1)
 	return 0;
 }
 
-int diff_flush_patch_id(struct diff_options *options, unsigned char *sha1)
+int diff_flush_patch_id(struct diff_options *options, unsigned char *sha1, int diff_header_only)
 {
 	struct diff_queue_struct *q = &diff_queued_diff;
 	int i;
-	int result = diff_get_patch_id(options, sha1);
+	int result = diff_get_patch_id(options, sha1, diff_header_only);
 
 	for (i = 0; i < q->nr; i++)
 		diff_free_filepair(q->queue[i]);