apply: handle exact renames

Deltas containing exact renames are special; they simple indicate that a
file was renamed without providing additional metadata (like the
filemode).  Teach the reader to provide the file mode and use the
preimage's filemode in the case that the delta does not provide one.)

src/apply.c

@@ -433,6 +433,7 @@ static int apply_one(
 	char *filename = NULL;
 	unsigned int mode;
 	git_oid pre_id, post_id;
+	git_filemode_t pre_filemode;
 	git_index_entry pre_entry, post_entry;
 	int error;
 
@@ -453,7 +454,7 @@ static int apply_one(
 	}
 
 	if (delta->status != GIT_DELTA_ADDED) {
-		error = git_reader_read(&pre_contents, &pre_id,
+		error = git_reader_read(&pre_contents, &pre_id, &pre_filemode,
 			preimage_reader, delta->old_file.path);
 
 		/* ENOTFOUND means the preimage was not found; apply failed. */
@@ -477,11 +478,15 @@ static int apply_one(
 		 * application.  (Without this, we would fail to write the
 		 * postimage contents to any file that had been modified
 		 * from HEAD on-disk, even if the patch application succeeded.)
+		 * Use the contents from the delta where available - some
+		 * fields may not be available, like the old file mode (eg in
+		 * an exact rename situation) so trust the patch parsing to
+		 * validate and use the preimage data in that case.
 		 */
 		if (preimage) {
 			memset(&pre_entry, 0, sizeof(git_index_entry));
 			pre_entry.path = delta->old_file.path;
-			pre_entry.mode = delta->old_file.mode;
+			pre_entry.mode = delta->old_file.mode ? delta->old_file.mode : pre_filemode;
 			git_oid_cpy(&pre_entry.id, &pre_id);
 
 			if ((error = git_index_add(preimage, &pre_entry)) < 0)

src/reader.c

@@ -25,6 +25,7 @@ typedef struct {
 static int tree_reader_read(
 	git_buf *out,
 	git_oid *out_id,
+	git_filemode_t *out_filemode,
 	git_reader *_reader,
 	const char *filename)
 {
@@ -41,6 +42,9 @@ static int tree_reader_read(
 	if (out_id)
 		git_oid_cpy(out_id, git_tree_entry_id(tree_entry));
 
+	if (out_filemode)
+		*out_filemode = git_tree_entry_filemode(tree_entry);
+
 done:
 	git_blob_free(blob);
 	git_tree_entry_free(tree_entry);
@@ -74,6 +78,7 @@ typedef struct {
 static int workdir_reader_read(
 	git_buf *out,
 	git_oid *out_id,
+	git_filemode_t *out_filemode,
 	git_reader *_reader,
 	const char *filename)
 {
@@ -130,6 +135,9 @@ static int workdir_reader_read(
 	if (out_id)
 		git_oid_cpy(out_id, &id);
 
+	if (out_filemode)
+		*out_filemode = filemode;
+
 done:
 	git_filter_list_free(filters);
 	git_buf_dispose(&path);
@@ -173,6 +181,7 @@ typedef struct {
 static int index_reader_read(
 	git_buf *out,
 	git_oid *out_id,
+	git_filemode_t *out_filemode,
 	git_reader *_reader,
 	const char *filename)
 {
@@ -190,6 +199,9 @@ static int index_reader_read(
 	if (out_id)
 		git_oid_cpy(out_id, &entry->id);
 
+	if (out_filemode)
+		*out_filemode = entry->mode;
+
 	error = git_blob__getbuf(out, blob);
 
 done:
@@ -229,12 +241,13 @@ int git_reader_for_index(
 int git_reader_read(
 	git_buf *out,
 	git_oid *out_id,
+	git_filemode_t *out_filemode,
 	git_reader *reader,
 	const char *filename)
 {
 	assert(out && reader && filename);
 
-	return reader->read(out, out_id, reader, filename);
+	return reader->read(out, out_id, out_filemode, reader, filename);
 }
 
 void git_reader_free(git_reader *reader)

src/reader.h

@@ -25,7 +25,7 @@ typedef struct git_reader git_reader;
  * reader after disposing the underlying object that it reads.
  */
 struct git_reader {
-	int (*read)(git_buf *out, git_oid *out_oid, git_reader *reader, const char *filename);
+	int (*read)(git_buf *out, git_oid *out_oid, git_filemode_t *mode, git_reader *reader, const char *filename);
 };
 
 /**
@@ -93,6 +93,7 @@ extern int git_reader_for_workdir(
 extern int git_reader_read(
 	git_buf *out,
 	git_oid *out_id,
+	git_filemode_t *out_filemode,
 	git_reader *reader,
 	const char *filename);
 

tests/apply/apply_helpers.h

@@ -112,6 +112,12 @@
 	"+but the shin OR knuckle is the nicest.\n" \
 	"+Another new line.\n" \
 
+#define DIFF_RENAME_FILE \
+	"diff --git a/beef.txt b/notbeef.txt\n" \
+	"similarity index 100%\n" \
+	"rename from beef.txt\n" \
+	"rename to notbeef.txt\n"
+
 #define DIFF_RENAME_AND_MODIFY_FILE \
 	"diff --git a/beef.txt b/notbeef.txt\n" \
 	"similarity index 97%\n" \

tests/apply/both.c

@@ -400,6 +400,31 @@ void test_apply_both__honors_crlf_attributes(void)
 	git_diff_free(diff);
 }
 
+void test_apply_both__rename(void)
+{
+	git_diff *diff;
+
+	struct merge_index_entry both_expected[] = {
+		{ 0100644, "f51658077d85f2264fa179b4d0848268cb3475c3", 0, "asparagus.txt" },
+		{ 0100644, "4b7c5650008b2e747fe1809eeb5a1dde0e80850a", 0, "bouilli.txt" },
+		{ 0100644, "c4e6cca3ec6ae0148ed231f97257df8c311e015f", 0, "gravy.txt" },
+		{ 0100644, "68f6182f4c85d39e1309d97c7e456156dc9c0096", 0, "notbeef.txt" },
+		{ 0100644, "68af1fc7407fd9addf1701a87eb1c95c7494c598", 0, "oyster.txt" },
+		{ 0100644, "94d2c01087f48213bd157222d54edfefd77c9bba", 0, "veal.txt" },
+	};
+	size_t both_expected_cnt = sizeof(both_expected) /
+		sizeof(struct merge_index_entry);
+
+	cl_git_pass(git_diff_from_buffer(&diff, DIFF_RENAME_FILE,
+		strlen(DIFF_RENAME_FILE)));
+	cl_git_pass(git_apply(repo, diff, GIT_APPLY_LOCATION_BOTH, NULL));
+
+	validate_apply_index(repo, both_expected, both_expected_cnt);
+	validate_apply_workdir(repo, both_expected, both_expected_cnt);
+
+	git_diff_free(diff);
+}
+
 void test_apply_both__rename_and_modify(void)
 {
 	git_diff *diff;