Merge branch 'jc/lock-report-on-error'

Git 2.11 had a minor regression in "merge --ff-only" that competed
with another process that simultanously attempted to update the
index. We used to explain what went wrong with an error message,
but the new code silently failed.  The error message has been
resurrected.

* jc/lock-report-on-error:
  lockfile: LOCK_REPORT_ON_ERROR
  hold_locked_index(): align error handling with hold_lockfile_for_update()
  wt-status: implement opportunisitc index update correctly

22 files changed, 49 insertions, 36 deletions

diff --git a/apply.c b/apply.c
index 705cf562f0..2ed808d429 100644
--- a/apply.c
+++ b/apply.c
@@ -4688,7 +4688,7 @@ static int apply_patch(struct apply_state *state,
 								 state->index_file,
 								 LOCK_DIE_ON_ERROR);
 		else
-			state->newfd = hold_locked_index(state->lock_file, 1);
+			state->newfd = hold_locked_index(state->lock_file, LOCK_DIE_ON_ERROR);
 	}
 
 	if (state->check_index && read_apply_cache(state) < 0) {
diff --git a/builtin/add.c b/builtin/add.c
index e8fb80b36e..9f53f020d0 100644
--- a/builtin/add.c
+++ b/builtin/add.c
@@ -361,7 +361,7 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 	add_new_files = !take_worktree_changes && !refresh_only;
 	require_pathspec = !(take_worktree_changes || (0 < addremove_explicit));
 
-	hold_locked_index(&lock_file, 1);
+	hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 
 	flags = ((verbose ? ADD_CACHE_VERBOSE : 0) |
 		 (show_only ? ADD_CACHE_PRETEND : 0) |
diff --git a/builtin/am.c b/builtin/am.c
index 6981f42ce9..bb5da422fc 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1119,7 +1119,7 @@ static void refresh_and_write_cache(void)
 {
 	struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 
-	hold_locked_index(lock_file, 1);
+	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"));
@@ -1976,7 +1976,7 @@ static int fast_forward_to(struct tree *head, struct tree *remote, int reset)
 		return -1;
 
 	lock_file = xcalloc(1, sizeof(struct lock_file));
-	hold_locked_index(lock_file, 1);
+	hold_locked_index(lock_file, LOCK_DIE_ON_ERROR);
 
 	refresh_cache(REFRESH_QUIET);
 
@@ -2016,7 +2016,7 @@ static int merge_tree(struct tree *tree)
 		return -1;
 
 	lock_file = xcalloc(1, sizeof(struct lock_file));
-	hold_locked_index(lock_file, 1);
+	hold_locked_index(lock_file, LOCK_DIE_ON_ERROR);
 
 	memset(&opts, 0, sizeof(opts));
 	opts.head_idx = 1;
diff --git a/builtin/checkout-index.c b/builtin/checkout-index.c
index 30a49d9f42..07631d0c9c 100644
--- a/builtin/checkout-index.c
+++ b/builtin/checkout-index.c
@@ -205,7 +205,7 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 	if (index_opt && !state.base_dir_len && !to_tempfile) {
 		state.refresh_cache = 1;
 		state.istate = &the_index;
-		newfd = hold_locked_index(&lock_file, 1);
+		newfd = hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 	}
 
 	/* Check out named files first */
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 512492aad9..bfe685c198 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -274,7 +274,7 @@ static int checkout_paths(const struct checkout_opts *opts,
 
 	lock_file = xcalloc(1, sizeof(struct lock_file));
 
-	hold_locked_index(lock_file, 1);
+	hold_locked_index(lock_file, LOCK_DIE_ON_ERROR);
 	if (read_cache_preload(&opts->pathspec) < 0)
 		return error(_("index file corrupt"));
 
@@ -467,7 +467,7 @@ static int merge_working_tree(const struct checkout_opts *opts,
 	int ret;
 	struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 
-	hold_locked_index(lock_file, 1);
+	hold_locked_index(lock_file, LOCK_DIE_ON_ERROR);
 	if (read_cache_preload(NULL) < 0)
 		return error(_("index file corrupt"));
 
diff --git a/builtin/clone.c b/builtin/clone.c
index e3cb8082f7..5ef81927a6 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -711,7 +711,7 @@ static int checkout(int submodule_progress)
 	setup_work_tree();
 
 	lock_file = xcalloc(1, sizeof(struct lock_file));
-	hold_locked_index(lock_file, 1);
+	hold_locked_index(lock_file, LOCK_DIE_ON_ERROR);
 
 	memset(&opts, 0, sizeof opts);
 	opts.update = 1;
diff --git a/builtin/commit.c b/builtin/commit.c
index 0ed634b26c..711f96cc43 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -351,7 +351,7 @@ static const char *prepare_index(int argc, const char **argv, const char *prefix
 
 	if (interactive) {
 		char *old_index_env = NULL;
-		hold_locked_index(&index_lock, 1);
+		hold_locked_index(&index_lock, LOCK_DIE_ON_ERROR);
 
 		refresh_cache_or_die(refresh_flags);
 
@@ -396,7 +396,7 @@ static const char *prepare_index(int argc, const char **argv, const char *prefix
 	 * (B) on failure, rollback the real index.
 	 */
 	if (all || (also && pathspec.nr)) {
-		hold_locked_index(&index_lock, 1);
+		hold_locked_index(&index_lock, LOCK_DIE_ON_ERROR);
 		add_files_to_cache(also ? prefix : NULL, &pathspec, 0);
 		refresh_cache_or_die(refresh_flags);
 		update_main_cache_tree(WRITE_TREE_SILENT);
@@ -416,7 +416,7 @@ static const char *prepare_index(int argc, const char **argv, const char *prefix
 	 * We still need to refresh the index here.
 	 */
 	if (!only && !pathspec.nr) {
-		hold_locked_index(&index_lock, 1);
+		hold_locked_index(&index_lock, LOCK_DIE_ON_ERROR);
 		refresh_cache_or_die(refresh_flags);
 		if (active_cache_changed
 		    || !cache_tree_fully_valid(active_cache_tree))
@@ -468,7 +468,7 @@ static const char *prepare_index(int argc, const char **argv, const char *prefix
 	if (read_cache() < 0)
 		die(_("cannot read the index"));
 
-	hold_locked_index(&index_lock, 1);
+	hold_locked_index(&index_lock, LOCK_DIE_ON_ERROR);
 	add_remove_files(&partial);
 	refresh_cache(REFRESH_QUIET);
 	update_main_cache_tree(WRITE_TREE_SILENT);
diff --git a/builtin/merge.c b/builtin/merge.c
index b65eeaa87d..0070bf2556 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -634,7 +634,7 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 {
 	static struct lock_file lock;
 
-	hold_locked_index(&lock, 1);
+	hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 	refresh_cache(REFRESH_QUIET);
 	if (active_cache_changed &&
 	    write_locked_index(&the_index, &lock, COMMIT_LOCK))
@@ -671,7 +671,7 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 		for (j = common; j; j = j->next)
 			commit_list_insert(j->item, &reversed);
 
-		hold_locked_index(&lock, 1);
+		hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 		clean = merge_recursive(&o, head,
 				remoteheads->item, reversed, &result);
 		if (clean < 0)
@@ -781,7 +781,7 @@ static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 	struct commit_list *parents, **pptr = &parents;
 	static struct lock_file lock;
 
-	hold_locked_index(&lock, 1);
+	hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 	refresh_cache(REFRESH_QUIET);
 	if (active_cache_changed &&
 	    write_locked_index(&the_index, &lock, COMMIT_LOCK))
diff --git a/builtin/mv.c b/builtin/mv.c
index 2f43877bc9..43adf92ba6 100644
--- a/builtin/mv.c
+++ b/builtin/mv.c
@@ -126,7 +126,7 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 	if (--argc < 1)
 		usage_with_options(builtin_mv_usage, builtin_mv_options);
 
-	hold_locked_index(&lock_file, 1);
+	hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 	if (read_cache() < 0)
 		die(_("index file corrupt"));
 
diff --git a/builtin/read-tree.c b/builtin/read-tree.c
index 9bd1fd755e..fa6edb35b2 100644
--- a/builtin/read-tree.c
+++ b/builtin/read-tree.c
@@ -150,7 +150,7 @@ int cmd_read_tree(int argc, const char **argv, const char *unused_prefix)
 	argc = parse_options(argc, argv, unused_prefix, read_tree_options,
 			     read_tree_usage, 0);
 
-	hold_locked_index(&lock_file, 1);
+	hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 
 	prefix_set = opts.prefix ? 1 : 0;
 	if (1 < opts.merge + opts.reset + prefix_set)
diff --git a/builtin/reset.c b/builtin/reset.c
index c04ac076dc..8ab915bfcb 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -354,7 +354,7 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 
 	if (reset_type != SOFT) {
 		struct lock_file *lock = xcalloc(1, sizeof(*lock));
-		hold_locked_index(lock, 1);
+		hold_locked_index(lock, LOCK_DIE_ON_ERROR);
 		if (reset_type == MIXED) {
 			int flags = quiet ? REFRESH_QUIET : REFRESH_IN_PORCELAIN;
 			if (read_from_tree(&pathspec, &oid, intent_to_add))
diff --git a/builtin/rm.c b/builtin/rm.c
index 3f3e24eb36..7f15a3d7f8 100644
--- a/builtin/rm.c
+++ b/builtin/rm.c
@@ -292,7 +292,7 @@ int cmd_rm(int argc, const char **argv, const char *prefix)
 	if (!index_only)
 		setup_work_tree();
 
-	hold_locked_index(&lock_file, 1);
+	hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 
 	if (read_cache() < 0)
 		die(_("index file corrupt"));
diff --git a/builtin/update-index.c b/builtin/update-index.c
index f3f07e7f1c..d530e89368 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -1012,6 +1012,7 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 	/* We can't free this memory, it becomes part of a linked list parsed atexit() */
 	lock_file = xcalloc(1, sizeof(struct lock_file));
 
+	/* we will diagnose later if it turns out that we need to update it */
 	newfd = hold_locked_index(lock_file, 0);
 	if (newfd < 0)
 		lock_error = errno;
diff --git a/lockfile.c b/lockfile.c
index 9268cdf325..aa69210d8b 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -174,8 +174,16 @@ int hold_lock_file_for_update_timeout(struct lock_file *lk, const char *path,
 				      int flags, long timeout_ms)
 {
 	int fd = lock_file_timeout(lk, path, flags, timeout_ms);
-	if (fd < 0 && (flags & LOCK_DIE_ON_ERROR))
-		unable_to_lock_die(path, errno);
+	if (fd < 0) {
+		if (flags & LOCK_DIE_ON_ERROR)
+			unable_to_lock_die(path, errno);
+		if (flags & LOCK_REPORT_ON_ERROR) {
+			struct strbuf buf = STRBUF_INIT;
+			unable_to_lock_message(path, errno, &buf);
+			error("%s", buf.buf);
+			strbuf_release(&buf);
+		}
+	}
 	return fd;
 }
 
diff --git a/lockfile.h b/lockfile.h
index d26ad27b2b..16775a7d79 100644
--- a/lockfile.h
+++ b/lockfile.h
@@ -129,11 +129,17 @@ struct lock_file {
 /*
  * If a lock is already taken for the file, `die()` with an error
  * message. If this flag is not specified, trying to lock a file that
- * is already locked returns -1 to the caller.
+ * is already locked silently returns -1 to the caller, or ...
  */
 #define LOCK_DIE_ON_ERROR 1
 
 /*
+ * ... this flag can be passed instead to return -1 and give the usual
+ * error message upon an error.
+ */
+#define LOCK_REPORT_ON_ERROR 2
+
+/*
  * Usually symbolic links in the destination path are resolved. This
  * means that (1) the lockfile is created by adding ".lock" to the
  * resolved path, and (2) upon commit, the resolved path is
diff --git a/merge-recursive.c b/merge-recursive.c
index 23d6992f40..d327209443 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -2133,7 +2133,7 @@ int merge_recursive_generic(struct merge_options *o,
 		}
 	}
 
-	hold_locked_index(lock, 1);
+	hold_locked_index(lock, LOCK_DIE_ON_ERROR);
 	clean = merge_recursive(o, head_commit, next_commit, ca,
 			result);
 	if (clean < 0)
diff --git a/merge.c b/merge.c
index 23866c9165..04ee5fc911 100644
--- a/merge.c
+++ b/merge.c
@@ -57,7 +57,7 @@ int checkout_fast_forward(const unsigned char *head,
 
 	refresh_cache(REFRESH_QUIET);
 
-	if (hold_locked_index(lock_file, 0) < 0)
+	if (hold_locked_index(lock_file, LOCK_REPORT_ON_ERROR) < 0)
 		return -1;
 
 	memset(&trees, 0, sizeof(trees));
diff --git a/read-cache.c b/read-cache.c
index db5d910642..f92a912dcb 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1425,12 +1425,9 @@ static int read_index_extension(struct index_state *istate,
 	return 0;
 }
 
-int hold_locked_index(struct lock_file *lk, int die_on_error)
+int hold_locked_index(struct lock_file *lk, int lock_flags)
 {
-	return hold_lock_file_for_update(lk, get_index_file(),
-					 die_on_error
-					 ? LOCK_DIE_ON_ERROR
-					 : 0);
+	return hold_lock_file_for_update(lk, get_index_file(), lock_flags);
 }
 
 int read_index(struct index_state *istate)
diff --git a/rerere.c b/rerere.c
index 5d083ca572..3bd55caf3b 100644
--- a/rerere.c
+++ b/rerere.c
@@ -708,7 +708,7 @@ static void update_paths(struct string_list *update)
 {
 	int i;
 
-	hold_locked_index(&index_lock, 1);
+	hold_locked_index(&index_lock, LOCK_DIE_ON_ERROR);
 
 	for (i = 0; i < update->nr; i++) {
 		struct string_list_item *item = &update->items[i];
diff --git a/sequencer.c b/sequencer.c
index 050e28bbc3..28061dcb78 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -323,7 +323,7 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
 	char **xopt;
 	static struct lock_file index_lock;
 
-	hold_locked_index(&index_lock, 1);
+	hold_locked_index(&index_lock, LOCK_DIE_ON_ERROR);
 
 	read_cache();
 
diff --git a/t/helper/test-scrap-cache-tree.c b/t/helper/test-scrap-cache-tree.c
index 27fe0405b8..d2a63bea43 100644
--- a/t/helper/test-scrap-cache-tree.c
+++ b/t/helper/test-scrap-cache-tree.c
@@ -8,7 +8,7 @@ static struct lock_file index_lock;
 int cmd_main(int ac, const char **av)
 {
 	setup_git_directory();
-	hold_locked_index(&index_lock, 1);
+	hold_locked_index(&index_lock, LOCK_DIE_ON_ERROR);
 	if (read_cache() < 0)
 		die("unable to read index file");
 	active_cache_tree = NULL;
diff --git a/wt-status.c b/wt-status.c
index a2e9d332d8..a715e71906 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -2258,11 +2258,12 @@ int has_uncommitted_changes(int ignore_submodules)
 int require_clean_work_tree(const char *action, const char *hint, int ignore_submodules, int gently)
 {
 	struct lock_file *lock_file = xcalloc(1, sizeof(*lock_file));
-	int err = 0;
+	int err = 0, fd;
 
-	hold_locked_index(lock_file, 0);
+	fd = hold_locked_index(lock_file, 0);
 	refresh_cache(REFRESH_QUIET);
-	update_index_if_able(&the_index, lock_file);
+	if (0 <= fd)
+		update_index_if_able(&the_index, lock_file);
 	rollback_lock_file(lock_file);
 
 	if (has_unstaged_changes(ignore_submodules)) {