"git checkout -- paths..." should error out when paths cannot be written

When "git checkout -- paths..." cannot update work tree for whatever
reason, checkout_entry() correctly issued an error message for the path to
the end user, but the command ignored the error, causing the entire
command to succeed.  This fixes it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-checkout.c

@@ -84,6 +84,7 @@ static int checkout_paths(struct tree *source_tree, const char **pathspec)
 	unsigned char rev[20];
 	int flag;
 	struct commit *head;
+	int errs = 0;
 
 	int newfd;
 	struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
@@ -106,13 +107,14 @@ static int checkout_paths(struct tree *source_tree, const char **pathspec)
 	if (report_path_error(ps_matched, pathspec, 0))
 		return 1;
 
+	/* Now we are committed to check them out */
 	memset(&state, 0, sizeof(state));
 	state.force = 1;
 	state.refresh_cache = 1;
 	for (pos = 0; pos < active_nr; pos++) {
 		struct cache_entry *ce = active_cache[pos];
 		if (pathspec_match(pathspec, NULL, ce->name, 0)) {
-			checkout_entry(ce, &state, NULL);
+			errs |= checkout_entry(ce, &state, NULL);
 		}
 	}
 
@@ -123,7 +125,8 @@ static int checkout_paths(struct tree *source_tree, const char **pathspec)
 	resolve_ref("HEAD", rev, 0, &flag);
 	head = lookup_commit_reference_gently(rev, 1);
 
-	return post_checkout_hook(head, head, 0);
+	errs |= post_checkout_hook(head, head, 0);
+	return errs;
 }
 
 static void show_local_changes(struct object *head)