#include "pathspec.h"
 #include "dir.h"
 #include "split-index.h"
+#include "fsmonitor.h"
 
 /*
  * Default to not allowing changes to the list of files. The
 static int verbose;
 static int mark_valid_only;
 static int mark_skip_worktree_only;
+static int mark_fsmonitor_only;
 #define MARK_FLAG 1
 #define UNMARK_FLAG 2
 static struct strbuf mtime_dir = STRBUF_INIT;
        int namelen = strlen(path);
        int pos = cache_name_pos(path, namelen);
        if (0 <= pos) {
+               mark_fsmonitor_invalid(&the_index, active_cache[pos]);
                if (mark)
                        active_cache[pos]->ce_flags |= flag;
                else
                if (S_ISGITLINK(ce->ce_mode)) {
 
                        /* Do nothing to the index if there is no HEAD! */
-                       if (resolve_gitlink_ref(path, "HEAD", oid.hash) < 0)
+                       if (resolve_gitlink_ref(path, "HEAD", &oid) < 0)
                                return 0;
 
                        return add_one_path(ce, path, len, st);
        }
 
        /* No match - should we add it as a gitlink? */
-       if (!resolve_gitlink_ref(path, "HEAD", oid.hash))
+       if (!resolve_gitlink_ref(path, "HEAD", &oid))
                return add_one_path(NULL, path, len, st);
 
        /* Error out. */
                        die("Unable to mark file %s", path);
                return;
        }
+       if (mark_fsmonitor_only) {
+               if (mark_ce_flags(path, CE_FSMONITOR_VALID, mark_fsmonitor_only == MARK_FLAG))
+                       die("Unable to mark file %s", path);
+               return;
+       }
 
        if (force_remove) {
                if (remove_file_from_cache(path))
 
 static void read_head_pointers(void)
 {
-       if (read_ref("HEAD", head_oid.hash))
+       if (read_ref("HEAD", &head_oid))
                die("No HEAD -- no initial commit yet?");
-       if (read_ref("MERGE_HEAD", merge_head_oid.hash)) {
+       if (read_ref("MERGE_HEAD", &merge_head_oid)) {
                fprintf(stderr, "Not in the middle of a merge.\n");
                exit(0);
        }
                       PATHSPEC_PREFER_CWD,
                       prefix, av + 1);
 
-       if (read_ref("HEAD", head_oid.hash))
+       if (read_ref("HEAD", &head_oid))
                /* If there is no HEAD, that means it is an initial
                 * commit.  Update everything in the index.
                 */
        struct refresh_params refresh_args = {0, &has_errors};
        int lock_error = 0;
        int split_index = -1;
+       int force_write = 0;
+       int fsmonitor = -1;
        struct lock_file lock_file = LOCK_INIT;
        struct parse_opt_ctx_t ctx;
        strbuf_getline_fn getline_fn;
                            N_("test if the filesystem supports untracked cache"), UC_TEST),
                OPT_SET_INT(0, "force-untracked-cache", &untracked_cache,
                            N_("enable untracked cache without testing the filesystem"), UC_FORCE),
+               OPT_SET_INT(0, "force-write-index", &force_write,
+                       N_("write out the index even if is not flagged as changed"), 1),
+               OPT_BOOL(0, "fsmonitor", &fsmonitor,
+                       N_("enable or disable file system monitor")),
+               {OPTION_SET_INT, 0, "fsmonitor-valid", &mark_fsmonitor_only, NULL,
+                       N_("mark files as fsmonitor valid"),
+                       PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, MARK_FLAG},
+               {OPTION_SET_INT, 0, "no-fsmonitor-valid", &mark_fsmonitor_only, NULL,
+                       N_("clear fsmonitor valid bit"),
+                       PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, UNMARK_FLAG},
                OPT_END()
        };
 
                die("BUG: bad untracked_cache value: %d", untracked_cache);
        }
 
-       if (active_cache_changed) {
+       if (fsmonitor > 0) {
+               if (git_config_get_fsmonitor() == 0)
+                       warning(_("core.fsmonitor is unset; "
+                               "set it if you really want to "
+                               "enable fsmonitor"));
+               add_fsmonitor(&the_index);
+               report(_("fsmonitor enabled"));
+       } else if (!fsmonitor) {
+               if (git_config_get_fsmonitor() == 1)
+                       warning(_("core.fsmonitor is set; "
+                               "remove it if you really want to "
+                               "disable fsmonitor"));
+               remove_fsmonitor(&the_index);
+               report(_("fsmonitor disabled"));
+       }
+
+       if (active_cache_changed || force_write) {
                if (newfd < 0) {
                        if (refresh_args.flags & REFRESH_QUIET)
                                exit(128);