diff --git a/builtin/am.c b/builtin/am.c
index ee7305eaa6..39a70fc79a 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1071,19 +1071,6 @@ static const char *msgnum(const struct am_state *state)
 	return sb.buf;
 }
 
-/**
- * Refresh and write index.
- */
-static void refresh_and_write_cache(void)
-{
-	struct lock_file lock_file = LOCK_INIT;
-
-	hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
-	refresh_cache(REFRESH_QUIET);
-	if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
-		die(_("unable to write index file"));
-}
-
 /**
  * Dies with a user-friendly message on how to proceed after resolving the
  * problem. This message can be overridden with state->resolvemsg.
@@ -1705,7 +1692,8 @@ static void am_run(struct am_state *state, int resume)
 
 	unlink(am_path(state, "dirtyindex"));
 
-	refresh_and_write_cache();
+	if (refresh_and_write_cache(REFRESH_QUIET, 0, 0) < 0)
+		die(_("unable to write index file"));
 
 	if (repo_index_has_changes(the_repository, NULL, &sb)) {
 		write_state_bool(state, "dirtyindex", 1);
diff --git a/builtin/merge.c b/builtin/merge.c
index c9746e37b8..062e911441 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -688,16 +688,13 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 			      struct commit_list *remoteheads,
 			      struct commit *head)
 {
-	struct lock_file lock = LOCK_INIT;
 	const char *head_arg = "HEAD";
 
-	hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
-	refresh_cache(REFRESH_QUIET);
-	if (write_locked_index(&the_index, &lock,
-			       COMMIT_LOCK | SKIP_IF_UNCHANGED))
+	if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 		return error(_("Unable to write index."));
 
 	if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
+		struct lock_file lock = LOCK_INIT;
 		int clean, x;
 		struct commit *result;
 		struct commit_list *reversed = NULL;
@@ -872,12 +869,8 @@ static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 {
 	struct object_id result_tree, result_commit;
 	struct commit_list *parents, **pptr = &parents;
-	struct lock_file lock = LOCK_INIT;
 
-	hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
-	refresh_cache(REFRESH_QUIET);
-	if (write_locked_index(&the_index, &lock,
-			       COMMIT_LOCK | SKIP_IF_UNCHANGED))
+	if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 		return error(_("Unable to write index."));
 
 	write_tree_trivial(&result_tree);
diff --git a/builtin/stash.c b/builtin/stash.c
index b5a301f24d..ab30d1e920 100644
--- a/builtin/stash.c
+++ b/builtin/stash.c
@@ -396,7 +396,7 @@ static int do_apply_stash(const char *prefix, struct stash_info *info,
 	const struct object_id *bases[1];
 
 	read_cache_preload(NULL);
-	if (refresh_cache(REFRESH_QUIET))
+	if (refresh_and_write_cache(REFRESH_QUIET, 0, 0))
 		return -1;
 
 	if (write_cache_as_tree(&c_tree, 0, NULL))
@@ -485,7 +485,7 @@ static int do_apply_stash(const char *prefix, struct stash_info *info,
 	}
 
 	if (quiet) {
-		if (refresh_cache(REFRESH_QUIET))
+		if (refresh_and_write_cache(REFRESH_QUIET, 0, 0))
 			warning("could not refresh index");
 	} else {
 		struct child_process cp = CHILD_PROCESS_INIT;
@@ -1129,7 +1129,10 @@ static int do_create_stash(const struct pathspec *ps, struct strbuf *stash_msg_b
 	prepare_fallback_ident("git stash", "git@stash");
 
 	read_cache_preload(NULL);
-	refresh_cache(REFRESH_QUIET);
+	if (refresh_and_write_cache(REFRESH_QUIET, 0, 0) < 0) {
+		ret = -1;
+		goto done;
+	}
 
 	if (get_oid("HEAD", &info->b_commit)) {
 		if (!quiet)
@@ -1290,7 +1293,7 @@ static int do_push_stash(const struct pathspec *ps, const char *stash_msg, int q
 		free(ps_matched);
 	}
 
-	if (refresh_cache(REFRESH_QUIET)) {
+	if (refresh_and_write_cache(REFRESH_QUIET, 0, 0)) {
 		ret = -1;
 		goto done;
 	}
diff --git a/cache.h b/cache.h
index 5624e6c02d..91e465fda2 100644
--- a/cache.h
+++ b/cache.h
@@ -414,6 +414,7 @@ extern struct index_state the_index;
 #define add_file_to_cache(path, flags) add_file_to_index(&the_index, (path), (flags))
 #define chmod_cache_entry(ce, flip) chmod_index_entry(&the_index, (ce), (flip))
 #define refresh_cache(flags) refresh_index(&the_index, (flags), NULL, NULL, NULL)
+#define refresh_and_write_cache(refresh_flags, write_flags, gentle) repo_refresh_and_write_index(the_repository, (refresh_flags), (write_flags), (gentle), NULL, NULL, NULL)
 #define ce_match_stat(ce, st, options) ie_match_stat(&the_index, (ce), (st), (options))
 #define ce_modified(ce, st, options) ie_modified(&the_index, (ce), (st), (options))
 #define cache_dir_exists(name, namelen) index_dir_exists(&the_index, (name), (namelen))
@@ -834,6 +835,23 @@ void fill_stat_cache_info(struct index_state *istate, struct cache_entry *ce, st
 #define REFRESH_IN_PORCELAIN	0x0020	/* user friendly output, not "needs update" */
 #define REFRESH_PROGRESS	0x0040  /* show progress bar if stderr is tty */
 int refresh_index(struct index_state *, unsigned int flags, const struct pathspec *pathspec, char *seen, const char *header_msg);
+/*
+ * Refresh the index and write it to disk.
+ *
+ * 'refresh_flags' is passed directly to 'refresh_index()', while
+ * 'COMMIT_LOCK | write_flags' is passed to 'write_locked_index()', so
+ * the lockfile is always either committed or rolled back.
+ *
+ * If 'gentle' is passed, errors locking the index are ignored.
+ *
+ * Return 1 if refreshing the index returns an error, -1 if writing
+ * the index to disk fails, 0 on success.
+ *
+ * Note that if refreshing the index returns an error, we still write
+ * out the index (unless locking fails).
+ */
+int repo_refresh_and_write_index(struct repository*, unsigned int refresh_flags, unsigned int write_flags, int gentle, const struct pathspec *, char *seen, const char *header_msg);
+
 struct cache_entry *refresh_cache_entry(struct index_state *, struct cache_entry *, unsigned int);
 
 void set_alternate_index_output(const char *);
diff --git a/read-cache.c b/read-cache.c
index cff1280975..2c1409491d 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1472,6 +1472,27 @@ static void show_file(const char * fmt, const char * name, int in_porcelain,
 	printf(fmt, name);
 }
 
+int repo_refresh_and_write_index(struct repository *repo,
+				 unsigned int refresh_flags,
+				 unsigned int write_flags,
+				 int gentle,
+				 const struct pathspec *pathspec,
+				 char *seen, const char *header_msg)
+{
+	struct lock_file lock_file = LOCK_INIT;
+	int fd, ret = 0;
+
+	fd = repo_hold_locked_index(repo, &lock_file, 0);
+	if (!gentle && fd < 0)
+		return -1;
+	if (refresh_index(repo->index, refresh_flags, pathspec, seen, header_msg))
+		ret = 1;
+	if (0 <= fd && write_locked_index(repo->index, &lock_file, COMMIT_LOCK | write_flags))
+		ret = -1;
+	return ret;
+}
+
+
 int refresh_index(struct index_state *istate, unsigned int flags,
 		  const struct pathspec *pathspec,
 		  char *seen, const char *header_msg)
diff --git a/t/t3903-stash.sh b/t/t3903-stash.sh
index 820b350aeb..580bfbdc23 100755
--- a/t/t3903-stash.sh
+++ b/t/t3903-stash.sh
@@ -1253,4 +1253,20 @@ test_expect_success 'stash --keep-index with file deleted in index does not resu
 	test_path_is_missing to-remove
 '
 
+test_expect_success 'stash apply should succeed with unmodified file' '
+	echo base >file &&
+	git add file &&
+	git commit -m base &&
+
+	# now stash a modification
+	echo modified >file &&
+	git stash &&
+
+	# make the file stat dirty
+	cp file other &&
+	mv other file &&
+
+	git stash apply
+'
+
 test_done