reset.c: move lock, write and commit out of update_index_refresh()

In preparation for the/a following patch, move the locking, writing
and committing of the index file out of update_index_refresh(). The
code duplication caused will soon be taken care of. What remains of
update_index_refresh() is just one line, but it is still called from
two places, so let's leave it for now.

In the process, we expose and fix the minor UI bug that makes us print
"Could not refresh index" when we fail to write the index file when
invoked with a pathspec. Copy the error message from the pathspec-less
codepath ("Could not write new index file.").

Signed-off-by: Martin von Zweigbergk <martinvonz@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/reset.c

@@ -109,19 +109,10 @@ static void print_new_head_line(struct commit *commit)
 		printf("\n");
 }
 
-static int update_index_refresh(int fd, struct lock_file *index_lock, int flags)
+static void update_index_refresh(int flags)
 {
-	if (!index_lock) {
-		index_lock = xcalloc(1, sizeof(struct lock_file));
-		fd = hold_locked_index(index_lock, 1);
-	}
-
 	refresh_index(&the_index, (flags), NULL, NULL,
 		      _("Unstaged changes after reset:"));
-	if (write_cache(fd, active_cache, active_nr) ||
-			commit_locked_index(index_lock))
-		return error ("Could not refresh index");
-	return 0;
 }
 
 static void update_index_from_diff(struct diff_queue_struct *q,
@@ -321,9 +312,14 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 	if (pathspec) {
 		struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 		int index_fd = hold_locked_index(lock, 1);
-		return read_from_tree(pathspec, sha1) ||
-			update_index_refresh(index_fd, lock,
-					quiet ? REFRESH_QUIET : REFRESH_IN_PORCELAIN);
+		if (read_from_tree(pathspec, sha1))
+			return 1;
+		update_index_refresh(
+			quiet ? REFRESH_QUIET : REFRESH_IN_PORCELAIN);
+		if (write_cache(index_fd, active_cache, active_nr) ||
+		    commit_locked_index(lock))
+			return error("Could not write new index file.");
+		return 0;
 	}
 
 	/* Soft reset does not touch the index file nor the working tree
@@ -351,9 +347,15 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 
 	if (reset_type == HARD && !update_ref_status && !quiet)
 		print_new_head_line(commit);
-	else if (reset_type == MIXED) /* Report what has not been updated. */
-		update_index_refresh(0, NULL,
-				quiet ? REFRESH_QUIET : REFRESH_IN_PORCELAIN);
+	else if (reset_type == MIXED) { /* Report what has not been updated. */
+		struct lock_file *index_lock = xcalloc(1, sizeof(struct lock_file));
+		int fd = hold_locked_index(index_lock, 1);
+		update_index_refresh(
+			quiet ? REFRESH_QUIET : REFRESH_IN_PORCELAIN);
+		if (write_cache(fd, active_cache, active_nr) ||
+		    commit_locked_index(index_lock))
+			error("Could not refresh index");
+	}
 
 	remove_branch_state();