1 files changed, 368 insertions, 96 deletions

diff --git a/builtin/worktree.c b/builtin/worktree.c
index cd62eef..7c6c725 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -1,12 +1,23 @@
-#include "cache.h"
+#include "builtin.h"
+#include "abspath.h"
+#include "advice.h"
 #include "checkout.h"
 #include "config.h"
-#include "builtin.h"
+#include "copy.h"
 #include "dir.h"
+#include "environment.h"
+#include "gettext.h"
+#include "hex.h"
+#include "object-file.h"
+#include "object-name.h"
 #include "parse-options.h"
+#include "path.h"
 #include "strvec.h"
 #include "branch.h"
+#include "read-cache-ll.h"
 #include "refs.h"
+#include "remote.h"
+#include "repository.h"
 #include "run-command.h"
 #include "hook.h"
 #include "sigchain.h"
@@ -15,15 +26,91 @@
 #include "worktree.h"
 #include "quote.h"
 
-static const char * const worktree_usage[] = {
-	N_("git worktree add [<options>] <path> [<commit-ish>]"),
-	N_("git worktree list [<options>]"),
-	N_("git worktree lock [<options>] <path>"),
-	N_("git worktree move <worktree> <new-path>"),
-	N_("git worktree prune [<options>]"),
-	N_("git worktree remove [<options>] <worktree>"),
-	N_("git worktree repair [<path>...]"),
-	N_("git worktree unlock <path>"),
+#define BUILTIN_WORKTREE_ADD_USAGE \
+	N_("git worktree add [-f] [--detach] [--checkout] [--lock [--reason <string>]]\n" \
+	   "                 [--orphan] [(-b | -B) <new-branch>] <path> [<commit-ish>]")
+
+#define BUILTIN_WORKTREE_LIST_USAGE \
+	N_("git worktree list [-v | --porcelain [-z]]")
+#define BUILTIN_WORKTREE_LOCK_USAGE \
+	N_("git worktree lock [--reason <string>] <worktree>")
+#define BUILTIN_WORKTREE_MOVE_USAGE \
+	N_("git worktree move <worktree> <new-path>")
+#define BUILTIN_WORKTREE_PRUNE_USAGE \
+	N_("git worktree prune [-n] [-v] [--expire <expire>]")
+#define BUILTIN_WORKTREE_REMOVE_USAGE \
+	N_("git worktree remove [-f] <worktree>")
+#define BUILTIN_WORKTREE_REPAIR_USAGE \
+	N_("git worktree repair [<path>...]")
+#define BUILTIN_WORKTREE_UNLOCK_USAGE \
+	N_("git worktree unlock <worktree>")
+
+#define WORKTREE_ADD_DWIM_ORPHAN_INFER_TEXT \
+	_("No possible source branch, inferring '--orphan'")
+
+#define WORKTREE_ADD_ORPHAN_WITH_DASH_B_HINT_TEXT \
+	_("If you meant to create a worktree containing a new unborn branch\n" \
+	"(branch with no commits) for this repository, you can do so\n" \
+	"using the --orphan flag:\n" \
+	"\n" \
+	"    git worktree add --orphan -b %s %s\n")
+
+#define WORKTREE_ADD_ORPHAN_NO_DASH_B_HINT_TEXT \
+	_("If you meant to create a worktree containing a new unborn branch\n" \
+	"(branch with no commits) for this repository, you can do so\n" \
+	"using the --orphan flag:\n" \
+	"\n" \
+	"    git worktree add --orphan %s\n")
+
+static const char * const git_worktree_usage[] = {
+	BUILTIN_WORKTREE_ADD_USAGE,
+	BUILTIN_WORKTREE_LIST_USAGE,
+	BUILTIN_WORKTREE_LOCK_USAGE,
+	BUILTIN_WORKTREE_MOVE_USAGE,
+	BUILTIN_WORKTREE_PRUNE_USAGE,
+	BUILTIN_WORKTREE_REMOVE_USAGE,
+	BUILTIN_WORKTREE_REPAIR_USAGE,
+	BUILTIN_WORKTREE_UNLOCK_USAGE,
+	NULL
+};
+
+static const char * const git_worktree_add_usage[] = {
+	BUILTIN_WORKTREE_ADD_USAGE,
+	NULL,
+};
+
+static const char * const git_worktree_list_usage[] = {
+	BUILTIN_WORKTREE_LIST_USAGE,
+	NULL
+};
+
+static const char * const git_worktree_lock_usage[] = {
+	BUILTIN_WORKTREE_LOCK_USAGE,
+	NULL
+};
+
+static const char * const git_worktree_move_usage[] = {
+	BUILTIN_WORKTREE_MOVE_USAGE,
+	NULL
+};
+
+static const char * const git_worktree_prune_usage[] = {
+	BUILTIN_WORKTREE_PRUNE_USAGE,
+	NULL
+};
+
+static const char * const git_worktree_remove_usage[] = {
+	BUILTIN_WORKTREE_REMOVE_USAGE,
+	NULL
+};
+
+static const char * const git_worktree_repair_usage[] = {
+	BUILTIN_WORKTREE_REPAIR_USAGE,
+	NULL
+};
+
+static const char * const git_worktree_unlock_usage[] = {
+	BUILTIN_WORKTREE_UNLOCK_USAGE,
 	NULL
 };
 
@@ -32,6 +119,7 @@ struct add_opts {
 	int detach;
 	int quiet;
 	int checkout;
+	int orphan;
 	const char *keep_locked;
 };
 
@@ -40,14 +128,15 @@ static int verbose;
 static int guess_remote;
 static timestamp_t expire;
 
-static int git_worktree_config(const char *var, const char *value, void *cb)
+static int git_worktree_config(const char *var, const char *value,
+			       const struct config_context *ctx, void *cb)
 {
 	if (!strcmp(var, "worktree.guessremote")) {
 		guess_remote = git_config_bool(var, value);
 		return 0;
 	}
 
-	return git_default_config(var, value, cb);
+	return git_default_config(var, value, ctx, cb);
 }
 
 static int delete_git_dir(const char *id)
@@ -115,7 +204,7 @@ static void prune_worktrees(void)
 {
 	struct strbuf reason = STRBUF_INIT;
 	struct strbuf main_path = STRBUF_INIT;
-	struct string_list kept = STRING_LIST_INIT_NODUP;
+	struct string_list kept = STRING_LIST_INIT_DUP;
 	DIR *dir = opendir(git_path("worktrees"));
 	struct dirent *d;
 	if (!dir)
@@ -126,14 +215,14 @@ static void prune_worktrees(void)
 		if (should_prune_worktree(d->d_name, &reason, &path, expire))
 			prune_worktree(d->d_name, reason.buf);
 		else if (path)
-			string_list_append(&kept, path)->util = xstrdup(d->d_name);
+			string_list_append_nodup(&kept, path)->util = xstrdup(d->d_name);
 	}
 	closedir(dir);
 
 	strbuf_add_absolute_path(&main_path, get_git_common_dir());
 	/* massage main worktree absolute path to match 'gitdir' content */
 	strbuf_strip_suffix(&main_path, "/.");
-	string_list_append(&kept, strbuf_detach(&main_path, NULL));
+	string_list_append_nodup(&kept, strbuf_detach(&main_path, NULL));
 	prune_dups(&kept);
 	string_list_clear(&kept, 1);
 
@@ -153,9 +242,10 @@ static int prune(int ac, const char **av, const char *prefix)
 	};
 
 	expire = TIME_MAX;
-	ac = parse_options(ac, av, prefix, options, worktree_usage, 0);
+	ac = parse_options(ac, av, prefix, options, git_worktree_prune_usage,
+			   0);
 	if (ac)
-		usage_with_options(worktree_usage, options);
+		usage_with_options(git_worktree_prune_usage, options);
 	prune_worktrees();
 	return 0;
 }
@@ -260,7 +350,6 @@ static void copy_filtered_worktree_config(const char *worktree_git_dir)
 
 	if (file_exists(from_file)) {
 		struct config_set cs = { { 0 } };
-		const char *core_worktree;
 		int bare;
 
 		if (safe_create_leading_directories(to_file) ||
@@ -276,12 +365,12 @@ static void copy_filtered_worktree_config(const char *worktree_git_dir)
 		if (!git_configset_get_bool(&cs, "core.bare", &bare) &&
 			bare &&
 			git_config_set_multivar_in_file_gently(
-				to_file, "core.bare", NULL, "true", 0))
+				to_file, "core.bare", NULL, "true", NULL, 0))
 			error(_("failed to unset '%s' in '%s'"),
 				"core.bare", to_file);
-		if (!git_configset_get_value(&cs, "core.worktree", &core_worktree) &&
+		if (!git_configset_get(&cs, "core.worktree") &&
 			git_config_set_in_file_gently(to_file,
-							"core.worktree", NULL))
+							"core.worktree", NULL, NULL))
 			error(_("failed to unset '%s' in '%s'"),
 				"core.worktree", to_file);
 
@@ -305,13 +394,28 @@ static int checkout_worktree(const struct add_opts *opts,
 	return run_command(&cp);
 }
 
+static int make_worktree_orphan(const char * ref, const struct add_opts *opts,
+				struct strvec *child_env)
+{
+	struct strbuf symref = STRBUF_INIT;
+	struct child_process cp = CHILD_PROCESS_INIT;
+
+	validate_new_branchname(ref, &symref, 0);
+	strvec_pushl(&cp.args, "symbolic-ref", "HEAD", symref.buf, NULL);
+	if (opts->quiet)
+		strvec_push(&cp.args, "--quiet");
+	strvec_pushv(&cp.env, child_env->v);
+	strbuf_release(&symref);
+	cp.git_cmd = 1;
+	return run_command(&cp);
+}
+
 static int add_worktree(const char *path, const char *refname,
 			const struct add_opts *opts)
 {
 	struct strbuf sb_git = STRBUF_INIT, sb_repo = STRBUF_INIT;
 	struct strbuf sb = STRBUF_INIT, realpath = STRBUF_INIT;
 	const char *name;
-	struct child_process cp = CHILD_PROCESS_INIT;
 	struct strvec child_env = STRVEC_INIT;
 	unsigned int counter = 0;
 	int len, ret;
@@ -319,7 +423,8 @@ static int add_worktree(const char *path, const char *refname,
 	struct commit *commit = NULL;
 	int is_branch = 0;
 	struct strbuf sb_name = STRBUF_INIT;
-	struct worktree **worktrees;
+	struct worktree **worktrees, *wt = NULL;
+	struct ref_store *wt_refs;
 
 	worktrees = get_worktrees();
 	check_candidate_path(path, opts->force, worktrees, "add");
@@ -334,7 +439,7 @@ static int add_worktree(const char *path, const char *refname,
 			die_if_checked_out(symref.buf, 0);
 	}
 	commit = lookup_commit_reference_by_name(refname);
-	if (!commit)
+	if (!commit && !opts->orphan)
 		die(_("invalid reference: %s"), refname);
 
 	name = worktree_basename(path, &len);
@@ -390,21 +495,33 @@ static int add_worktree(const char *path, const char *refname,
 	strbuf_realpath(&realpath, get_git_common_dir(), 1);
 	write_file(sb_git.buf, "gitdir: %s/worktrees/%s",
 		   realpath.buf, name);
-	/*
-	 * This is to keep resolve_ref() happy. We need a valid HEAD
-	 * or is_git_directory() will reject the directory. Any value which
-	 * looks like an object ID will do since it will be immediately
-	 * replaced by the symbolic-ref or update-ref invocation in the new
-	 * worktree.
-	 */
-	strbuf_reset(&sb);
-	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
-	write_file(sb.buf, "%s", oid_to_hex(null_oid()));
 	strbuf_reset(&sb);
 	strbuf_addf(&sb, "%s/commondir", sb_repo.buf);
 	write_file(sb.buf, "../..");
 
 	/*
+	 * Set up the ref store of the worktree and create the HEAD reference.
+	 */
+	wt = get_linked_worktree(name, 1);
+	if (!wt) {
+		ret = error(_("could not find created worktree '%s'"), name);
+		goto done;
+	}
+	wt_refs = get_worktree_ref_store(wt);
+
+	ret = refs_init_db(wt_refs, REFS_INIT_DB_IS_WORKTREE, &sb);
+	if (ret)
+		goto done;
+
+	if (!is_branch && commit)
+		ret = refs_update_ref(wt_refs, NULL, "HEAD", &commit->object.oid,
+				      NULL, 0, UPDATE_REFS_MSG_ON_ERR);
+	else
+		ret = refs_create_symref(wt_refs, "HEAD", symref.buf, NULL);
+	if (ret)
+		goto done;
+
+	/*
 	 * If the current worktree has sparse-checkout enabled, then copy
 	 * the sparse-checkout patterns from the current worktree.
 	 */
@@ -416,26 +533,14 @@ static int add_worktree(const char *path, const char *refname,
 	 * values from the current worktree into the new one, that way the
 	 * new worktree behaves the same as this one.
 	 */
-	if (repository_format_worktree_config)
+	if (the_repository->repository_format_worktree_config)
 		copy_filtered_worktree_config(sb_repo.buf);
 
 	strvec_pushf(&child_env, "%s=%s", GIT_DIR_ENVIRONMENT, sb_git.buf);
 	strvec_pushf(&child_env, "%s=%s", GIT_WORK_TREE_ENVIRONMENT, path);
-	cp.git_cmd = 1;
-
-	if (!is_branch)
-		strvec_pushl(&cp.args, "update-ref", "HEAD",
-			     oid_to_hex(&commit->object.oid), NULL);
-	else {
-		strvec_pushl(&cp.args, "symbolic-ref", "HEAD",
-			     symref.buf, NULL);
-		if (opts->quiet)
-			strvec_push(&cp.args, "--quiet");
-	}
 
-	strvec_pushv(&cp.env, child_env.v);
-	ret = run_command(&cp);
-	if (ret)
+	if (opts->orphan &&
+	    (ret = make_worktree_orphan(refname, opts, &child_env)))
 		goto done;
 
 	if (opts->checkout &&
@@ -457,7 +562,7 @@ done:
 	 * Hook failure does not warrant worktree deletion, so run hook after
 	 * is_junk is cleared, but do return appropriate code when hook fails.
 	 */
-	if (!ret && opts->checkout) {
+	if (!ret && opts->checkout && !opts->orphan) {
 		struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT;
 
 		strvec_pushl(&opt.env, "GIT_DIR", "GIT_WORK_TREE", NULL);
@@ -478,6 +583,7 @@ done:
 	strbuf_release(&sb_git);
 	strbuf_release(&sb_name);
 	strbuf_release(&realpath);
+	free_worktree(wt);
 	return ret;
 }
 
@@ -493,7 +599,7 @@ static void print_preparing_worktree_line(int detach,
 		else
 			fprintf_ln(stderr, _("Preparing worktree (resetting branch '%s'; was at %s)"),
 				  new_branch,
-				  find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV));
+				  repo_find_unique_abbrev(the_repository, &commit->object.oid, DEFAULT_ABBREV));
 	} else if (new_branch) {
 		fprintf_ln(stderr, _("Preparing worktree (new branch '%s')"), new_branch);
 	} else {
@@ -505,14 +611,131 @@ static void print_preparing_worktree_line(int detach,
 		else {
 			struct commit *commit = lookup_commit_reference_by_name(branch);
 			if (!commit)
-				die(_("invalid reference: %s"), branch);
+				BUG(_("unreachable: invalid reference: %s"), branch);
 			fprintf_ln(stderr, _("Preparing worktree (detached HEAD %s)"),
-				  find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV));
+				  repo_find_unique_abbrev(the_repository, &commit->object.oid, DEFAULT_ABBREV));
 		}
 		strbuf_release(&s);
 	}
 }
 
+/**
+ * Callback to short circuit iteration over refs on the first reference
+ * corresponding to a valid oid.
+ *
+ * Returns 0 on failure and non-zero on success.
+ */
+static int first_valid_ref(const char *refname UNUSED,
+			   const struct object_id *oid UNUSED,
+			   int flags UNUSED,
+			   void *cb_data UNUSED)
+{
+	return 1;
+}
+
+/**
+ * Verifies HEAD and determines whether there exist any valid local references.
+ *
+ * - Checks whether HEAD points to a valid reference.
+ *
+ * - Checks whether any valid local branches exist.
+ *
+ * - Emits a warning if there exist any valid branches but HEAD does not point
+ *   to a valid reference.
+ *
+ * Returns 1 if any of the previous checks are true, otherwise returns 0.
+ */
+static int can_use_local_refs(const struct add_opts *opts)
+{
+	if (head_ref(first_valid_ref, NULL)) {
+		return 1;
+	} else if (for_each_branch_ref(first_valid_ref, NULL)) {
+		if (!opts->quiet) {
+			struct strbuf path = STRBUF_INIT;
+			struct strbuf contents = STRBUF_INIT;
+
+			strbuf_add_real_path(&path, get_worktree_git_dir(NULL));
+			strbuf_addstr(&path, "/HEAD");
+			strbuf_read_file(&contents, path.buf, 64);
+			strbuf_stripspace(&contents, NULL);
+			strbuf_strip_suffix(&contents, "\n");
+
+			warning(_("HEAD points to an invalid (or orphaned) reference.\n"
+				  "HEAD path: '%s'\n"
+				  "HEAD contents: '%s'"),
+				  path.buf, contents.buf);
+			strbuf_release(&path);
+			strbuf_release(&contents);
+		}
+		return 1;
+	}
+	return 0;
+}
+
+/**
+ * Reports whether the necessary flags were set and whether the repository has
+ * remote references to attempt DWIM tracking of upstream branches.
+ *
+ * 1. Checks that `--guess-remote` was used or `worktree.guessRemote = true`.
+ *
+ * 2. Checks whether any valid remote branches exist.
+ *
+ * 3. Checks that there exists at least one remote and emits a warning/error
+ *    if both checks 1. and 2. are false (can be bypassed with `--force`).
+ *
+ * Returns 1 if checks 1. and 2. are true, otherwise 0.
+ */
+static int can_use_remote_refs(const struct add_opts *opts)
+{
+	if (!guess_remote) {
+		return 0;
+	} else if (for_each_remote_ref(first_valid_ref, NULL)) {
+		return 1;
+	} else if (!opts->force && remote_get(NULL)) {
+		die(_("No local or remote refs exist despite at least one remote\n"
+		      "present, stopping; use 'add -f' to override or fetch a remote first"));
+	}
+	return 0;
+}
+
+/**
+ * Determines whether `--orphan` should be inferred in the evaluation of
+ * `worktree add path/` or `worktree add -b branch path/` and emits an error
+ * if the supplied arguments would produce an illegal combination when the
+ * `--orphan` flag is included.
+ *
+ * `opts` and `opt_track` contain the other options & flags supplied to the
+ * command.
+ *
+ * remote determines whether to check `can_use_remote_refs()` or not. This
+ * is primarily to differentiate between the basic `add` DWIM and `add -b`.
+ *
+ * Returns 1 when inferring `--orphan`, 0 otherwise, and emits an error when
+ * `--orphan` is inferred but doing so produces an illegal combination of
+ * options and flags. Additionally produces an error when remote refs are
+ * checked and the repo is in a state that looks like the user added a remote
+ * but forgot to fetch (and did not override the warning with -f).
+ */
+static int dwim_orphan(const struct add_opts *opts, int opt_track, int remote)
+{
+	if (can_use_local_refs(opts)) {
+		return 0;
+	} else if (remote && can_use_remote_refs(opts)) {
+		return 0;
+	} else if (!opts->quiet) {
+		fprintf_ln(stderr, WORKTREE_ADD_DWIM_ORPHAN_INFER_TEXT);
+	}
+
+	if (opt_track) {
+		die(_("options '%s' and '%s' cannot be used together"),
+		    "--orphan", "--track");
+	} else if (!opts->checkout) {
+		die(_("options '%s' and '%s' cannot be used together"),
+		    "--orphan", "--no-checkout");
+	}
+	return 1;
+}
+
 static const char *dwim_branch(const char *path, const char **new_branch)
 {
 	int n;
@@ -549,6 +772,7 @@ static int add(int ac, const char **av, const char *prefix)
 	const char *opt_track = NULL;
 	const char *lock_reason = NULL;
 	int keep_locked = 0;
+	int used_new_branch_options;
 	struct option options[] = {
 		OPT__FORCE(&opts.force,
 			   N_("checkout <branch> even if already checked out in other worktree"),
@@ -557,6 +781,7 @@ static int add(int ac, const char **av, const char *prefix)
 			   N_("create a new branch")),
 		OPT_STRING('B', NULL, &new_branch_force, N_("branch"),
 			   N_("create or reset a branch")),
+		OPT_BOOL(0, "orphan", &opts.orphan, N_("create unborn branch")),
 		OPT_BOOL('d', "detach", &opts.detach, N_("detach HEAD at named commit")),
 		OPT_BOOL(0, "checkout", &opts.checkout, N_("populate the new working tree")),
 		OPT_BOOL(0, "lock", &keep_locked, N_("keep the new working tree locked")),
@@ -570,12 +795,25 @@ static int add(int ac, const char **av, const char *prefix)
 			 N_("try to match the new branch name with a remote-tracking branch")),
 		OPT_END()
 	};
+	int ret;
 
 	memset(&opts, 0, sizeof(opts));
 	opts.checkout = 1;
-	ac = parse_options(ac, av, prefix, options, worktree_usage, 0);
+	ac = parse_options(ac, av, prefix, options, git_worktree_add_usage, 0);
 	if (!!opts.detach + !!new_branch + !!new_branch_force > 1)
 		die(_("options '%s', '%s', and '%s' cannot be used together"), "-b", "-B", "--detach");
+	if (opts.detach && opts.orphan)
+		die(_("options '%s' and '%s' cannot be used together"),
+		    "--orphan", "--detach");
+	if (opts.orphan && opt_track)
+		die(_("options '%s' and '%s' cannot be used together"),
+		    "--orphan", "--track");
+	if (opts.orphan && !opts.checkout)
+		die(_("options '%s' and '%s' cannot be used together"),
+		    "--orphan", "--no-checkout");
+	if (opts.orphan && ac == 2)
+		die(_("option '%s' and commit-ish cannot be used together"),
+		    "--orphan");
 	if (lock_reason && !keep_locked)
 		die(_("the option '%s' requires '%s'"), "--reason", "--lock");
 	if (lock_reason)
@@ -584,10 +822,11 @@ static int add(int ac, const char **av, const char *prefix)
 		opts.keep_locked = _("added with --lock");
 
 	if (ac < 1 || ac > 2)
-		usage_with_options(worktree_usage, options);
+		usage_with_options(git_worktree_add_usage, options);
 
 	path = prefix_filename(prefix, av[0]);
 	branch = ac < 2 ? "HEAD" : av[1];
+	used_new_branch_options = new_branch || new_branch_force;
 
 	if (!strcmp(branch, "-"))
 		branch = "@{-1}";
@@ -604,13 +843,28 @@ static int add(int ac, const char **av, const char *prefix)
 		strbuf_release(&symref);
 	}
 
-	if (ac < 2 && !new_branch && !opts.detach) {
+	if (opts.orphan && !new_branch) {
+		int n;
+		const char *s = worktree_basename(path, &n);
+		new_branch = xstrndup(s, n);
+	} else if (opts.orphan) {
+		; /* no-op */
+	} else if (opts.detach) {
+		/* Check HEAD */
+		if (!strcmp(branch, "HEAD"))
+			can_use_local_refs(&opts);
+	} else if (ac < 2 && new_branch) {
+		/* DWIM: Infer --orphan when repo has no refs. */
+		opts.orphan = dwim_orphan(&opts, !!opt_track, 0);
+	} else if (ac < 2) {
+		/* DWIM: Guess branch name from path. */
 		const char *s = dwim_branch(path, &new_branch);
 		if (s)
 			branch = s;
-	}
 
-	if (ac == 2 && !new_branch && !opts.detach) {
+		/* DWIM: Infer --orphan when repo has no refs. */
+		opts.orphan = (!s) && dwim_orphan(&opts, !!opt_track, 1);
+	} else if (ac == 2) {
 		struct object_id oid;
 		struct commit *commit;
 		const char *remote;
@@ -623,11 +877,31 @@ static int add(int ac, const char **av, const char *prefix)
 				branch = remote;
 			}
 		}
+
+		if (!strcmp(branch, "HEAD"))
+			can_use_local_refs(&opts);
+
 	}
+
+	if (!opts.orphan && !lookup_commit_reference_by_name(branch)) {
+		int attempt_hint = !opts.quiet && (ac < 2);
+		if (attempt_hint && used_new_branch_options) {
+			advise_if_enabled(ADVICE_WORKTREE_ADD_ORPHAN,
+				WORKTREE_ADD_ORPHAN_WITH_DASH_B_HINT_TEXT,
+				new_branch, path);
+		} else if (attempt_hint) {
+			advise_if_enabled(ADVICE_WORKTREE_ADD_ORPHAN,
+				WORKTREE_ADD_ORPHAN_NO_DASH_B_HINT_TEXT, path);
+		}
+		die(_("invalid reference: %s"), branch);
+	}
+
 	if (!opts.quiet)
 		print_preparing_worktree_line(opts.detach, branch, new_branch, !!new_branch_force);
 
-	if (new_branch) {
+	if (opts.orphan) {
+		branch = new_branch;
+	} else if (new_branch) {
 		struct child_process cp = CHILD_PROCESS_INIT;
 		cp.git_cmd = 1;
 		strvec_push(&cp.args, "branch");
@@ -646,9 +920,9 @@ static int add(int ac, const char **av, const char *prefix)
 		die(_("--[no-]track can only be used if a new branch is created"));
 	}
 
-	UNLEAK(path);
-	UNLEAK(opts);
-	return add_worktree(path, branch, &opts);
+	ret = add_worktree(path, branch, &opts);
+	free(path);
+	return ret;
 }
 
 static void show_worktree_porcelain(struct worktree *wt, int line_terminator)
@@ -696,7 +970,7 @@ static void show_worktree(struct worktree *wt, int path_maxlen, int abbrev_len)
 		strbuf_addstr(&sb, "(bare)");
 	else {
 		strbuf_addf(&sb, "%-*s ", abbrev_len,
-				find_unique_abbrev(&wt->head_oid, DEFAULT_ABBREV));
+				repo_find_unique_abbrev(the_repository, &wt->head_oid, DEFAULT_ABBREV));
 		if (wt->is_detached)
 			strbuf_addstr(&sb, "(detached HEAD)");
 		else if (wt->head_ref) {
@@ -733,7 +1007,7 @@ static void measure_widths(struct worktree **wt, int *abbrev, int *maxlen)
 
 		if (path_len > *maxlen)
 			*maxlen = path_len;
-		sha1_len = strlen(find_unique_abbrev(&wt[i]->head_oid, *abbrev));
+		sha1_len = strlen(repo_find_unique_abbrev(the_repository, &wt[i]->head_oid, *abbrev));
 		if (sha1_len > *abbrev)
 			*abbrev = sha1_len;
 	}
@@ -772,9 +1046,9 @@ static int list(int ac, const char **av, const char *prefix)
 	};
 
 	expire = TIME_MAX;
-	ac = parse_options(ac, av, prefix, options, worktree_usage, 0);
+	ac = parse_options(ac, av, prefix, options, git_worktree_list_usage, 0);
 	if (ac)
-		usage_with_options(worktree_usage, options);
+		usage_with_options(git_worktree_list_usage, options);
 	else if (verbose && porcelain)
 		die(_("options '%s' and '%s' cannot be used together"), "--verbose", "--porcelain");
 	else if (!line_terminator && !porcelain)
@@ -811,9 +1085,9 @@ static int lock_worktree(int ac, const char **av, const char *prefix)
 	};
 	struct worktree **worktrees, *wt;
 
-	ac = parse_options(ac, av, prefix, options, worktree_usage, 0);
+	ac = parse_options(ac, av, prefix, options, git_worktree_lock_usage, 0);
 	if (ac != 1)
-		usage_with_options(worktree_usage, options);
+		usage_with_options(git_worktree_lock_usage, options);
 
 	worktrees = get_worktrees();
 	wt = find_worktree(worktrees, prefix, av[0]);
@@ -844,9 +1118,9 @@ static int unlock_worktree(int ac, const char **av, const char *prefix)
 	struct worktree **worktrees, *wt;
 	int ret;
 
-	ac = parse_options(ac, av, prefix, options, worktree_usage, 0);
+	ac = parse_options(ac, av, prefix, options, git_worktree_unlock_usage, 0);
 	if (ac != 1)
-		usage_with_options(worktree_usage, options);
+		usage_with_options(git_worktree_unlock_usage, options);
 
 	worktrees = get_worktrees();
 	wt = find_worktree(worktrees, prefix, av[0]);
@@ -863,7 +1137,7 @@ static int unlock_worktree(int ac, const char **av, const char *prefix)
 
 static void validate_no_submodules(const struct worktree *wt)
 {
-	struct index_state istate = { NULL };
+	struct index_state istate = INDEX_STATE_INIT(the_repository);
 	struct strbuf path = STRBUF_INIT;
 	int i, found_submodules = 0;
 
@@ -914,9 +1188,10 @@ static int move_worktree(int ac, const char **av, const char *prefix)
 	const char *reason = NULL;
 	char *path;
 
-	ac = parse_options(ac, av, prefix, options, worktree_usage, 0);
+	ac = parse_options(ac, av, prefix, options, git_worktree_move_usage,
+			   0);
 	if (ac != 2)
-		usage_with_options(worktree_usage, options);
+		usage_with_options(git_worktree_move_usage, options);
 
 	path = prefix_filename(prefix, av[1]);
 	strbuf_addstr(&dst, path);
@@ -1042,9 +1317,9 @@ static int remove_worktree(int ac, const char **av, const char *prefix)
 	const char *reason = NULL;
 	int ret = 0;
 
-	ac = parse_options(ac, av, prefix, options, worktree_usage, 0);
+	ac = parse_options(ac, av, prefix, options, git_worktree_remove_usage, 0);
 	if (ac != 1)
-		usage_with_options(worktree_usage, options);
+		usage_with_options(git_worktree_remove_usage, options);
 
 	worktrees = get_worktrees();
 	wt = find_worktree(worktrees, prefix, av[0]);
@@ -1102,7 +1377,7 @@ static int repair(int ac, const char **av, const char *prefix)
 	};
 	int rc = 0;
 
-	ac = parse_options(ac, av, prefix, options, worktree_usage, 0);
+	ac = parse_options(ac, av, prefix, options, git_worktree_repair_usage, 0);
 	p = ac > 0 ? av : self;
 	for (; *p; p++)
 		repair_worktree_at_path(*p, report_repair, &rc);
@@ -1112,31 +1387,28 @@ static int repair(int ac, const char **av, const char *prefix)
 
 int cmd_worktree(int ac, const char **av, const char *prefix)
 {
+	parse_opt_subcommand_fn *fn = NULL;
 	struct option options[] = {
+		OPT_SUBCOMMAND("add", &fn, add),
+		OPT_SUBCOMMAND("prune", &fn, prune),
+		OPT_SUBCOMMAND("list", &fn, list),
+		OPT_SUBCOMMAND("lock", &fn, lock_worktree),
+		OPT_SUBCOMMAND("unlock", &fn, unlock_worktree),
+		OPT_SUBCOMMAND("move", &fn, move_worktree),
+		OPT_SUBCOMMAND("remove", &fn, remove_worktree),
+		OPT_SUBCOMMAND("repair", &fn, repair),
 		OPT_END()
 	};
 
 	git_config(git_worktree_config, NULL);
 
-	if (ac < 2)
-		usage_with_options(worktree_usage, options);
 	if (!prefix)
 		prefix = "";
-	if (!strcmp(av[1], "add"))
-		return add(ac - 1, av + 1, prefix);
-	if (!strcmp(av[1], "prune"))
-		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);
-	if (!strcmp(av[1], "move"))
-		return move_worktree(ac - 1, av + 1, prefix);
-	if (!strcmp(av[1], "remove"))
-		return remove_worktree(ac - 1, av + 1, prefix);
-	if (!strcmp(av[1], "repair"))
-		return repair(ac - 1, av + 1, prefix);
-	usage_with_options(worktree_usage, options);
+
+	ac = parse_options(ac, av, prefix, options, git_worktree_usage, 0);
+
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
+
+	return fn(ac, av, prefix);
 }