preserve mtime of local clone

A local clone without hardlinks copies all objects, including dangling
ones, to the new repository. Since the mtimes are renewed, those
dangling objects cannot be pruned by "git gc --prune", even if they
would have been old enough for pruning in the original repository.

Instead, preserve mtime during copy. "git gc --prune" will then work
in the clone just like it did in the original.
Signed-off-by: NClemens Buchacher <drizzd@aon.at>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-clone.c

@@ -269,7 +269,7 @@ static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest)
 				die_errno("failed to create link '%s'", dest->buf);
 			option_no_hardlinks = 1;
 		}
-		if (copy_file(dest->buf, src->buf, 0666))
+		if (copy_file_with_time(dest->buf, src->buf, 0666))
 			die_errno("failed to copy file to '%s'", dest->buf);
 	}
 	closedir(dir);

cache.h

@@ -923,6 +923,7 @@ extern const char *git_mailmap_file;
 extern void maybe_flush_or_die(FILE *, const char *);
 extern int copy_fd(int ifd, int ofd);
 extern int copy_file(const char *dst, const char *src, int mode);
+extern int copy_file_with_time(const char *dst, const char *src, int mode);
 extern void write_or_die(int fd, const void *buf, size_t count);
 extern int write_or_whine(int fd, const void *buf, size_t count, const char *msg);
 extern int write_or_whine_pipe(int fd, const void *buf, size_t count, const char *msg);

copy.c

@@ -35,6 +35,19 @@ int copy_fd(int ifd, int ofd)
 	return 0;
 }
 
+static int copy_times(const char *dst, const char *src)
+{
+	struct stat st;
+	struct utimbuf times;
+	if (stat(src, &st) < 0)
+		return -1;
+	times.actime = st.st_atime;
+	times.modtime = st.st_mtime;
+	if (utime(dst, &times) < 0)
+		return -1;
+	return 0;
+}
+
 int copy_file(const char *dst, const char *src, int mode)
 {
 	int fdi, fdo, status;
@@ -55,3 +68,11 @@ int copy_file(const char *dst, const char *src, int mode)
 
 	return status;
 }
+
+int copy_file_with_time(const char *dst, const char *src, int mode)
+{
+	int status = copy_file(dst, src, mode);
+	if (!status)
+		return copy_times(dst, src);
+	return status;
+}