diff --git a/builtin-diff-index.c b/builtin-diff-index.c
index 95a3db156b..083599d5c4 100644
--- a/builtin-diff-index.c
+++ b/builtin-diff-index.c
@@ -38,5 +38,9 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 	if (rev.pending.nr != 1 ||
 	    rev.max_count != -1 || rev.min_age != -1 || rev.max_age != -1)
 		usage(diff_cache_usage);
+	if (read_cache() < 0) {
+		perror("read_cache");
+		return -1;
+	}
 	return run_diff_index(&rev, cached);
 }
diff --git a/builtin-diff.c b/builtin-diff.c
index 54bbf025d9..45faa2067a 100644
--- a/builtin-diff.c
+++ b/builtin-diff.c
@@ -117,6 +117,10 @@ static int builtin_diff_index(struct rev_info *revs,
 	    revs->max_count != -1 || revs->min_age != -1 ||
 	    revs->max_age != -1)
 		usage(builtin_diff_usage);
+	if (read_cache() < 0) {
+		perror("read_cache");
+		return -1;
+	}
 	return run_diff_index(revs, cached);
 }
 
diff --git a/builtin-update-index.c b/builtin-update-index.c
index 772aaba7bb..65246dad8d 100644
--- a/builtin-update-index.c
+++ b/builtin-update-index.c
@@ -487,6 +487,7 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 	int prefix_length = prefix ? strlen(prefix) : 0;
 	char set_executable_bit = 0;
 	unsigned int refresh_flags = 0;
+	int lock_error = 0;
 	struct lock_file *lock_file;
 
 	git_config(git_default_config);
@@ -494,7 +495,9 @@ 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));
 
-	newfd = hold_lock_file_for_update(lock_file, get_index_file(), 1);
+	newfd = hold_lock_file_for_update(lock_file, get_index_file(), 0);
+	if (newfd < 0)
+		lock_error = errno;
 
 	entries = read_cache();
 	if (entries < 0)
@@ -651,6 +654,12 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 
  finish:
 	if (active_cache_changed) {
+		if (newfd < 0) {
+			if (refresh_flags & REFRESH_QUIET)
+				exit(128);
+			die("unable to create '%s.lock': %s",
+			    get_index_file(), strerror(lock_error));
+		}
 		if (write_cache(newfd, active_cache, active_nr) ||
 		    close(newfd) || commit_lock_file(lock_file))
 			die("Unable to write new index file");
diff --git a/diff-lib.c b/diff-lib.c
index a9b5149d1b..1d184422a5 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -217,6 +217,10 @@ int run_diff_files_cmd(struct rev_info *revs, int argc, const char **argv)
 		return 0;
 	}
 
+	if (read_cache() < 0) {
+		perror("read_cache");
+		return -1;
+	}
 	return run_diff_files(revs, silent_on_removed);
 }
 
@@ -227,11 +231,7 @@ int run_diff_files(struct rev_info *revs, int silent_on_removed)
 
 	if (diff_unmerged_stage < 0)
 		diff_unmerged_stage = 2;
-	entries = read_cache();
-	if (entries < 0) {
-		perror("read_cache");
-		return -1;
-	}
+	entries = active_nr;
 	for (i = 0; i < entries; i++) {
 		struct stat st;
 		unsigned int oldmode, newmode;
@@ -559,10 +559,6 @@ int run_diff_index(struct rev_info *revs, int cached)
 	if (!revs->ignore_merges)
 		match_missing = 1;
 
-	if (read_cache() < 0) {
-		perror("read_cache");
-		return -1;
-	}
 	mark_merge_entries();
 
 	ent = revs->pending.objects[0].item;
diff --git a/git-commit.sh b/git-commit.sh
index ec506d956f..cfa15110f6 100755
--- a/git-commit.sh
+++ b/git-commit.sh
@@ -13,10 +13,10 @@ git-rev-parse --verify HEAD >/dev/null 2>&1 || initial_commit=t
 case "$0" in
 *status)
 	status_only=t
-	unmerged_ok_if_status=--unmerged ;;
+	;;
 *commit)
 	status_only=
-	unmerged_ok_if_status= ;;
+	;;
 esac
 
 refuse_partial () {
@@ -389,16 +389,17 @@ else
 	USE_INDEX="$THIS_INDEX"
 fi
 
-GIT_INDEX_FILE="$USE_INDEX" \
-	git-update-index -q $unmerged_ok_if_status --refresh || exit
-
-################################################################
-# If the request is status, just show it and exit.
-
-case "$0" in
-*status)
+case "$status_only" in
+t)
+	# This will silently fail in a read-only repository, which is
+	# what we want.
+	GIT_INDEX_FILE="$USE_INDEX" git-update-index -q --unmerged --refresh
 	run_status
 	exit $?
+	;;
+'')
+	GIT_INDEX_FILE="$USE_INDEX" git-update-index -q --refresh || exit
+	;;
 esac
 
 ################################################################
diff --git a/wt-status.c b/wt-status.c
index 2879c3d5ec..e346511153 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -191,12 +191,18 @@ static void wt_status_print_changed_cb(struct diff_queue_struct *q,
 		wt_status_print_trailer();
 }
 
+static void wt_read_cache(struct wt_status *s)
+{
+	discard_cache();
+	read_cache();
+}
+
 void wt_status_print_initial(struct wt_status *s)
 {
 	int i;
 	char buf[PATH_MAX];
 
-	read_cache();
+	wt_read_cache(s);
 	if (active_nr) {
 		s->commitable = 1;
 		wt_status_print_cached_header(NULL);
@@ -220,6 +226,7 @@ static void wt_status_print_updated(struct wt_status *s)
 	rev.diffopt.format_callback = wt_status_print_updated_cb;
 	rev.diffopt.format_callback_data = s;
 	rev.diffopt.detect_rename = 1;
+	wt_read_cache(s);
 	run_diff_index(&rev, 1);
 }
 
@@ -231,6 +238,7 @@ static void wt_status_print_changed(struct wt_status *s)
 	rev.diffopt.output_format |= DIFF_FORMAT_CALLBACK;
 	rev.diffopt.format_callback = wt_status_print_changed_cb;
 	rev.diffopt.format_callback_data = s;
+	wt_read_cache(s);
 	run_diff_files(&rev, 0);
 }
 
@@ -287,6 +295,7 @@ static void wt_status_print_verbose(struct wt_status *s)
 	setup_revisions(0, NULL, &rev, s->reference);
 	rev.diffopt.output_format |= DIFF_FORMAT_PATCH;
 	rev.diffopt.detect_rename = 1;
+	wt_read_cache(s);
 	run_diff_index(&rev, 1);
 }
 
@@ -316,7 +325,6 @@ void wt_status_print(struct wt_status *s)
 	}
 	else {
 		wt_status_print_updated(s);
-		discard_cache();
 	}
 
 	wt_status_print_changed(s);