Do query the fsmonitor again after the index has been discarded

cache.h

@@ -338,7 +338,8 @@ struct index_state {
 	struct cache_time timestamp;
 	unsigned name_hash_initialized : 1,
 		 initialized : 1,
-		 drop_cache_tree : 1;
+		 drop_cache_tree : 1,
+		 fsmonitor_has_run_once : 1;
 	struct hashmap name_hash;
 	struct hashmap dir_hash;
 	struct object_id oid;

fsmonitor.c

@@ -129,17 +129,16 @@ static void fsmonitor_refresh_callback(struct index_state *istate, const char *n
 
 void refresh_fsmonitor(struct index_state *istate)
 {
-	static int has_run_once = 0;
 	struct strbuf query_result = STRBUF_INIT;
 	int query_success = 0;
 	size_t bol; /* beginning of line */
 	uint64_t last_update;
 	char *buf;
 	int i;
 
-	if (!core_fsmonitor || has_run_once)
+	if (!core_fsmonitor || istate->fsmonitor_has_run_once)
 		return;
-	has_run_once = 1;
+	istate->fsmonitor_has_run_once = 1;
 
 	trace_printf_key(&trace_fsmonitor, "refresh fsmonitor");
 	/*

read-cache.c

@@ -2307,6 +2307,7 @@ int discard_index(struct index_state *istate)
 	free_name_hash(istate);
 	cache_tree_free(&(istate->cache_tree));
 	istate->initialized = 0;
+	istate->fsmonitor_has_run_once = 0;
 	FREE_AND_NULL(istate->cache);
 	istate->cache_alloc = 0;
 	discard_split_index(istate);

t/helper/test-read-cache.c

@@ -1,14 +1,36 @@
 #include "test-tool.h"
 #include "cache.h"
+#include "config.h"
 
 int cmd__read_cache(int argc, const char **argv)
 {
-	int i, cnt = 1;
+	int i, cnt = 1, namelen;
+	const char *name = NULL;
+
+	if (argc > 1 && skip_prefix(argv[1], "--print-and-refresh=", &name)) {
+		namelen = strlen(name);
+		argc--;
+		argv++;
+	}
+
 	if (argc == 2)
 		cnt = strtol(argv[1], NULL, 0);
 	setup_git_directory();
+	git_config(git_default_config, NULL);
 	for (i = 0; i < cnt; i++) {
 		read_cache();
+		if (name) {
+			int pos;
+
+			refresh_index(&the_index, REFRESH_QUIET,
+				      NULL, NULL, NULL);
+			pos = index_name_pos(&the_index, name, namelen);
+			if (pos < 0)
+				die("%s not in index", name);
+			printf("%s is%s up to date\n", name,
+			       ce_uptodate(the_index.cache[pos]) ? "" : " not");
+			write_file(name, "%d\n", i);
+		}
 		discard_cache();
 	}
 	return 0;

t/t7519-status-fsmonitor.sh

@@ -346,4 +346,12 @@ test_expect_success UNTRACKED_CACHE 'ignore .git changes when invalidating UNTR'
 	test_cmp before after
 '
 
+test_expect_success 'discard_index() also discards fsmonitor info' '
+	test_config core.fsmonitor "$TEST_DIRECTORY/t7519/fsmonitor-all" &&
+	test_might_fail git update-index --refresh &&
+	test-tool read-cache --print-and-refresh=tracked 2 >actual &&
+	printf "tracked is%s up to date\n" "" " not" >expect &&
+	test_cmp expect actual
+'
+
 test_done