diff --git a/Documentation/git-worktree.txt b/Documentation/git-worktree.txt
index 7c4cfb0885..0aeb020d02 100644
--- a/Documentation/git-worktree.txt
+++ b/Documentation/git-worktree.txt
@@ -11,7 +11,9 @@ SYNOPSIS
 [verse]
 'git worktree add' [-f] [--detach] [--checkout] [-b <new-branch>] <path> [<branch>]
 'git worktree list' [--porcelain]
+'git worktree lock' [--reason <string>] <worktree>
 'git worktree prune' [-n] [-v] [--expire <expire>]
+'git worktree unlock' <worktree>
 
 DESCRIPTION
 -----------
@@ -38,9 +40,8 @@ section "DETAILS" for more information.
 
 If a linked working tree is stored on a portable device or network share
 which is not always mounted, you can prevent its administrative files from
-being pruned by creating a file named 'locked' alongside the other
-administrative files, optionally containing a plain text reason that
-pruning should be suppressed. See section "DETAILS" for more information.
+being pruned by issuing the `git worktree lock` command, optionally
+specifying `--reason` to explain why the working tree is locked.
 
 COMMANDS
 --------
@@ -62,10 +63,22 @@ each of the linked worktrees.  The output details include if the worktree is
 bare, the revision currently checked out, and the branch currently checked out
 (or 'detached HEAD' if none).
 
+lock::
+
+If a working tree is on a portable device or network share which
+is not always mounted, lock it to prevent its administrative
+files from being pruned automatically. This also prevents it from
+being moved or deleted. Optionally, specify a reason for the lock
+with `--reason`.
+
 prune::
 
 Prune working tree information in $GIT_DIR/worktrees.
 
+unlock::
+
+Unlock a working tree, allowing it to be pruned, moved or deleted.
+
 OPTIONS
 -------
 
@@ -111,6 +124,18 @@ OPTIONS
 --expire <time>::
 	With `prune`, only expire unused working trees older than <time>.
 
+--reason <string>::
+	With `lock`, an explanation why the working tree is locked.
+
+<worktree>::
+	Working trees can be identified by path, either relative or
+	absolute.
++
+If the last path components in the working tree's path is unique among
+working trees, it can be used to identify worktrees. For example if
+you only have to working trees at "/abc/def/ghi" and "/abc/def/ggg",
+then "ghi" or "def/ghi" is enough to point to the former working tree.
+
 DETAILS
 -------
 Each linked working tree has a private sub-directory in the repository's
@@ -151,7 +176,8 @@ instead.
 
 To prevent a $GIT_DIR/worktrees entry from being pruned (which
 can be useful in some situations, such as when the
-entry's working tree is stored on a portable device), add a file named
+entry's working tree is stored on a portable device), use the
+`git worktree lock` command, which adds a file named
 'locked' to the entry's directory. The file contains the reason in
 plain text. For example, if a linked working tree's `.git` file points
 to `/path/main/.git/worktrees/test-next` then a file named
@@ -227,8 +253,6 @@ performed manually, such as:
 - `remove` to remove a linked working tree and its administrative files (and
   warn if the working tree is dirty)
 - `mv` to move or rename a working tree and update its administrative files
-- `lock` to prevent automatic pruning of administrative files (for instance,
-  for a working tree on a portable device)
 
 GIT
 ---
diff --git a/builtin/worktree.c b/builtin/worktree.c
index cce555cbbc..5a41788edb 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -14,7 +14,9 @@
 static const char * const worktree_usage[] = {
 	N_("git worktree add [<options>] <path> [<branch>]"),
 	N_("git worktree list [<options>]"),
+	N_("git worktree lock [<options>] <path>"),
 	N_("git worktree prune [<options>]"),
+	N_("git worktree unlock <path>"),
 	NULL
 };
 
@@ -462,6 +464,66 @@ static int list(int ac, const char **av, const char *prefix)
 	return 0;
 }
 
+static int lock_worktree(int ac, const char **av, const char *prefix)
+{
+	const char *reason = "", *old_reason;
+	struct option options[] = {
+		OPT_STRING(0, "reason", &reason, N_("string"),
+			   N_("reason for locking")),
+		OPT_END()
+	};
+	struct worktree **worktrees, *wt;
+
+	ac = parse_options(ac, av, prefix, options, worktree_usage, 0);
+	if (ac != 1)
+		usage_with_options(worktree_usage, options);
+
+	worktrees = get_worktrees();
+	wt = find_worktree(worktrees, prefix, av[0]);
+	if (!wt)
+		die(_("'%s' is not a working tree"), av[0]);
+	if (is_main_worktree(wt))
+		die(_("The main working tree cannot be locked or unlocked"));
+
+	old_reason = is_worktree_locked(wt);
+	if (old_reason) {
+		if (*old_reason)
+			die(_("'%s' is already locked, reason: %s"),
+			    av[0], old_reason);
+		die(_("'%s' is already locked"), av[0]);
+	}
+
+	write_file(git_common_path("worktrees/%s/locked", wt->id),
+		   "%s", reason);
+	free_worktrees(worktrees);
+	return 0;
+}
+
+static int unlock_worktree(int ac, const char **av, const char *prefix)
+{
+	struct option options[] = {
+		OPT_END()
+	};
+	struct worktree **worktrees, *wt;
+	int ret;
+
+	ac = parse_options(ac, av, prefix, options, worktree_usage, 0);
+	if (ac != 1)
+		usage_with_options(worktree_usage, options);
+
+	worktrees = get_worktrees();
+	wt = find_worktree(worktrees, prefix, av[0]);
+	if (!wt)
+		die(_("'%s' is not a working tree"), av[0]);
+	if (is_main_worktree(wt))
+		die(_("The main working tree cannot be locked or unlocked"));
+	if (!is_worktree_locked(wt))
+		die(_("'%s' is not locked"), av[0]);
+	ret = unlink_or_warn(git_common_path("worktrees/%s/locked", wt->id));
+	free_worktrees(worktrees);
+	return ret;
+}
+
 int cmd_worktree(int ac, const char **av, const char *prefix)
 {
 	struct option options[] = {
@@ -478,5 +540,9 @@ int cmd_worktree(int ac, const char **av, const char *prefix)
 		return prune(ac - 1, av + 1, prefix);
 	if (!strcmp(av[1], "list"))
 		return list(ac - 1, av + 1, prefix);
+	if (!strcmp(av[1], "lock"))
+		return lock_worktree(ac - 1, av + 1, prefix);
+	if (!strcmp(av[1], "unlock"))
+		return unlock_worktree(ac - 1, av + 1, prefix);
 	usage_with_options(worktree_usage, options);
 }
diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 37888f4e57..10f6d52254 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -2693,7 +2693,7 @@ _git_whatchanged ()
 
 _git_worktree ()
 {
-	local subcommands="add list prune"
+	local subcommands="add list lock prune unlock"
 	local subcommand="$(__git_find_on_cmdline "$subcommands")"
 	if [ -z "$subcommand" ]; then
 		__gitcomp "$subcommands"
@@ -2705,6 +2705,9 @@ _git_worktree ()
 		list,--*)
 			__gitcomp "--porcelain"
 			;;
+		lock,--*)
+			__gitcomp "--reason"
+			;;
 		prune,--*)
 			__gitcomp "--dry-run --expire --verbose"
 			;;
diff --git a/t/t2028-worktree-move.sh b/t/t2028-worktree-move.sh
new file mode 100755
index 0000000000..8298aaf97f
--- /dev/null
+++ b/t/t2028-worktree-move.sh
@@ -0,0 +1,62 @@
+#!/bin/sh
+
+test_description='test git worktree move, remove, lock and unlock'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_commit init &&
+	git worktree add source &&
+	git worktree list --porcelain | grep "^worktree" >actual &&
+	cat <<-EOF >expected &&
+	worktree $(pwd)
+	worktree $(pwd)/source
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'lock main worktree' '
+	test_must_fail git worktree lock .
+'
+
+test_expect_success 'lock linked worktree' '
+	git worktree lock --reason hahaha source &&
+	echo hahaha >expected &&
+	test_cmp expected .git/worktrees/source/locked
+'
+
+test_expect_success 'lock linked worktree from another worktree' '
+	rm .git/worktrees/source/locked &&
+	git worktree add elsewhere &&
+	git -C elsewhere worktree lock --reason hahaha ../source &&
+	echo hahaha >expected &&
+	test_cmp expected .git/worktrees/source/locked
+'
+
+test_expect_success 'lock worktree twice' '
+	test_must_fail git worktree lock source &&
+	echo hahaha >expected &&
+	test_cmp expected .git/worktrees/source/locked
+'
+
+test_expect_success 'lock worktree twice (from the locked worktree)' '
+	test_must_fail git -C source worktree lock . &&
+	echo hahaha >expected &&
+	test_cmp expected .git/worktrees/source/locked
+'
+
+test_expect_success 'unlock main worktree' '
+	test_must_fail git worktree unlock .
+'
+
+test_expect_success 'unlock linked worktree' '
+	git worktree unlock source &&
+	test_path_is_missing .git/worktrees/source/locked
+'
+
+test_expect_success 'unlock worktree twice' '
+	test_must_fail git worktree unlock source &&
+	test_path_is_missing .git/worktrees/source/locked
+'
+
+test_done
diff --git a/worktree.c b/worktree.c
index b819baf0cd..5acfe4cd64 100644
--- a/worktree.c
+++ b/worktree.c
@@ -13,6 +13,7 @@ void free_worktrees(struct worktree **worktrees)
 		free(worktrees[i]->path);
 		free(worktrees[i]->id);
 		free(worktrees[i]->head_ref);
+		free(worktrees[i]->lock_reason);
 		free(worktrees[i]);
 	}
 	free (worktrees);
@@ -98,6 +99,8 @@ static struct worktree *get_main_worktree(void)
 	worktree->is_detached = is_detached;
 	worktree->is_current = 0;
 	add_head_info(&head_ref, worktree);
+	worktree->lock_reason = NULL;
+	worktree->lock_reason_valid = 0;
 
 done:
 	strbuf_release(&path);
@@ -143,6 +146,8 @@ static struct worktree *get_linked_worktree(const char *id)
 	worktree->is_detached = is_detached;
 	worktree->is_current = 0;
 	add_head_info(&head_ref, worktree);
+	worktree->lock_reason = NULL;
+	worktree->lock_reason_valid = 0;
 
 done:
 	strbuf_release(&path);
@@ -214,6 +219,78 @@ const char *get_worktree_git_dir(const struct worktree *wt)
 		return git_common_path("worktrees/%s", wt->id);
 }
 
+static struct worktree *find_worktree_by_suffix(struct worktree **list,
+						const char *suffix)
+{
+	struct worktree *found = NULL;
+	int nr_found = 0, suffixlen;
+
+	suffixlen = strlen(suffix);
+	if (!suffixlen)
+		return NULL;
+
+	for (; *list && nr_found < 2; list++) {
+		const char	*path	 = (*list)->path;
+		int		 pathlen = strlen(path);
+		int		 start	 = pathlen - suffixlen;
+
+		/* suffix must start at directory boundary */
+		if ((!start || (start > 0 && is_dir_sep(path[start - 1]))) &&
+		    !fspathcmp(suffix, path + start)) {
+			found = *list;
+			nr_found++;
+		}
+	}
+	return nr_found == 1 ? found : NULL;
+}
+
+struct worktree *find_worktree(struct worktree **list,
+			       const char *prefix,
+			       const char *arg)
+{
+	struct worktree *wt;
+	char *path;
+
+	if ((wt = find_worktree_by_suffix(list, arg)))
+		return wt;
+
+	arg = prefix_filename(prefix, strlen(prefix), arg);
+	path = xstrdup(real_path(arg));
+	for (; *list; list++)
+		if (!fspathcmp(path, real_path((*list)->path)))
+			break;
+	free(path);
+	return *list;
+}
+
+int is_main_worktree(const struct worktree *wt)
+{
+	return !wt->id;
+}
+
+const char *is_worktree_locked(struct worktree *wt)
+{
+	assert(!is_main_worktree(wt));
+
+	if (!wt->lock_reason_valid) {
+		struct strbuf path = STRBUF_INIT;
+
+		strbuf_addstr(&path, worktree_git_path(wt, "locked"));
+		if (file_exists(path.buf)) {
+			struct strbuf lock_reason = STRBUF_INIT;
+			if (strbuf_read_file(&lock_reason, path.buf, 0) < 0)
+				die_errno(_("failed to read '%s'"), path.buf);
+			strbuf_trim(&lock_reason);
+			wt->lock_reason = strbuf_detach(&lock_reason, NULL);
+		} else
+			wt->lock_reason = NULL;
+		wt->lock_reason_valid = 1;
+		strbuf_release(&path);
+	}
+
+	return wt->lock_reason;
+}
+
 int is_worktree_being_rebased(const struct worktree *wt,
 			      const char *target)
 {
diff --git a/worktree.h b/worktree.h
index 13949093cc..90e1311fa7 100644
--- a/worktree.h
+++ b/worktree.h
@@ -5,10 +5,12 @@ struct worktree {
 	char *path;
 	char *id;
 	char *head_ref;
+	char *lock_reason;	/* internal use */
 	unsigned char head_sha1[20];
 	int is_detached;
 	int is_bare;
 	int is_current;
+	int lock_reason_valid;
 };
 
 /* Functions for acting on the information about worktrees. */
@@ -29,6 +31,25 @@ extern struct worktree **get_worktrees(void);
  */
 extern const char *get_worktree_git_dir(const struct worktree *wt);
 
+/*
+ * Search a worktree that can be unambiguously identified by
+ * "arg". "prefix" must not be NULL.
+ */
+extern struct worktree *find_worktree(struct worktree **list,
+				      const char *prefix,
+				      const char *arg);
+
+/*
+ * Return true if the given worktree is the main one.
+ */
+extern int is_main_worktree(const struct worktree *wt);
+
+/*
+ * Return the reason string if the given worktree is locked or NULL
+ * otherwise.
+ */
+extern const char *is_worktree_locked(struct worktree *wt);
+
 /*
  * Free up the memory for worktree(s)
  */