worktree: add -z option for list subcommand

Add a -z option to be used in conjunction with --porcelain that gives
NUL-terminated output. As 'worktree list --porcelain' does not quote
worktree paths this enables it to handle worktree paths that contain
newlines.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-worktree.txt

@@ -10,7 +10,7 @@ SYNOPSIS
 --------
 [verse]
 'git worktree add' [-f] [--detach] [--checkout] [--lock [--reason <string>]] [-b <new-branch>] <path> [<commit-ish>]
-'git worktree list' [-v | --porcelain]
+'git worktree list' [-v | --porcelain [-z]]
 'git worktree lock' [--reason <string>] <worktree>
 'git worktree move' <worktree> <new-path>
 'git worktree prune' [-n] [-v] [--expire <expire>]
@@ -223,7 +223,14 @@ This can also be set up as the default behaviour by using the
 --porcelain::
 	With `list`, output in an easy-to-parse format for scripts.
 	This format will remain stable across Git versions and regardless of user
-	configuration.  See below for details.
+	configuration.  It is recommended to combine this with `-z`.
+	See below for details.
+
+-z::
+	Terminate each line with a NUL rather than a newline when
+	`--porcelain` is specified with `list`. This makes it possible
+	to parse the output when a worktree path contains a newline
+	character.
 
 -q::
 --quiet::
@@ -411,7 +418,8 @@ working tree itself.
 
 Porcelain Format
 ~~~~~~~~~~~~~~~~
-The porcelain format has a line per attribute.  Attributes are listed with a
+The porcelain format has a line per attribute.  If `-z` is given then the lines
+are terminated with NUL rather than a newline.  Attributes are listed with a
 label and value separated by a single space.  Boolean attributes (like `bare`
 and `detached`) are listed as a label only, and are present only
 if the value is true.  Some attributes (like `locked`) can be listed as a label
@@ -449,7 +457,7 @@ prunable gitdir file points to non-existent location
 
 ------------
 
-If the lock reason contains "unusual" characters such as newline, they
+Unless `-z` is used any "unusual" characters in the lock reason such as newlines
 are escaped and the entire reason is quoted as explained for the
 configuration variable `core.quotePath` (see linkgit:git-config[1]).
 For Example:

builtin/worktree.c

@@ -575,35 +575,37 @@ static int add(int ac, const char **av, const char *prefix)
 	return add_worktree(path, branch, &opts);
 }
 
-static void show_worktree_porcelain(struct worktree *wt)
+static void show_worktree_porcelain(struct worktree *wt, int line_terminator)
 {
 	const char *reason;
 
-	printf("worktree %s\n", wt->path);
+	printf("worktree %s%c", wt->path, line_terminator);
 	if (wt->is_bare)
-		printf("bare\n");
+		printf("bare%c", line_terminator);
 	else {
-		printf("HEAD %s\n", oid_to_hex(&wt->head_oid));
+		printf("HEAD %s%c", oid_to_hex(&wt->head_oid), line_terminator);
 		if (wt->is_detached)
-			printf("detached\n");
+			printf("detached%c", line_terminator);
 		else if (wt->head_ref)
-			printf("branch %s\n", wt->head_ref);
+			printf("branch %s%c", wt->head_ref, line_terminator);
 	}
 
 	reason = worktree_lock_reason(wt);
-	if (reason && *reason) {
-		struct strbuf sb = STRBUF_INIT;
-		quote_c_style(reason, &sb, NULL, 0);
-		printf("locked %s\n", sb.buf);
-		strbuf_release(&sb);
-	} else if (reason)
-		printf("locked\n");
+	if (reason) {
+		fputs("locked", stdout);
+		if (*reason) {
+			fputc(' ', stdout);
+			write_name_quoted(reason, stdout, line_terminator);
+		} else {
+			fputc(line_terminator, stdout);
+		}
+	}
 
 	reason = worktree_prune_reason(wt, expire);
 	if (reason)
-		printf("prunable %s\n", reason);
+		printf("prunable %s%c", reason, line_terminator);
 
-	printf("\n");
+	fputc(line_terminator, stdout);
 }
 
 static void show_worktree(struct worktree *wt, int path_maxlen, int abbrev_len)
@@ -681,12 +683,15 @@ static void pathsort(struct worktree **wt)
 static int list(int ac, const char **av, const char *prefix)
 {
 	int porcelain = 0;
+	int line_terminator = '\n';
 
 	struct option options[] = {
 		OPT_BOOL(0, "porcelain", &porcelain, N_("machine-readable output")),
 		OPT__VERBOSE(&verbose, N_("show extended annotations and reasons, if available")),
 		OPT_EXPIRY_DATE(0, "expire", &expire,
 				N_("add 'prunable' annotation to worktrees older than <time>")),
+		OPT_SET_INT('z', NULL, &line_terminator,
+			    N_("terminate records with a NUL character"), '\0'),
 		OPT_END()
 	};
 
@@ -696,6 +701,8 @@ static int list(int ac, const char **av, const char *prefix)
 		usage_with_options(worktree_usage, options);
 	else if (verbose && porcelain)
 		die(_("options '%s' and '%s' cannot be used together"), "--verbose", "--porcelain");
+	else if (!line_terminator && !porcelain)
+		die(_("the option '%s' requires '%s'"), "-z", "--porcelain");
 	else {
 		struct worktree **worktrees = get_worktrees();
 		int path_maxlen = 0, abbrev = DEFAULT_ABBREV, i;
@@ -708,7 +715,8 @@ static int list(int ac, const char **av, const char *prefix)
 
 		for (i = 0; worktrees[i]; i++) {
 			if (porcelain)
-				show_worktree_porcelain(worktrees[i]);
+				show_worktree_porcelain(worktrees[i],
+							line_terminator);
 			else
 				show_worktree(worktrees[i], path_maxlen, abbrev);
 		}

t/t2402-worktree-list.sh

@@ -64,6 +64,25 @@ test_expect_success '"list" all worktrees --porcelain' '
 	test_cmp expect actual
 '
 
+test_expect_success '"list" all worktrees --porcelain -z' '
+	test_when_finished "rm -rf here _actual actual expect &&
+				git worktree prune" &&
+	printf "worktree %sQHEAD %sQbranch %sQQ" \
+		"$(git rev-parse --show-toplevel)" \
+		$(git rev-parse HEAD --symbolic-full-name HEAD) >expect &&
+	git worktree add --detach here main &&
+	printf "worktree %sQHEAD %sQdetachedQQ" \
+		"$(git -C here rev-parse --show-toplevel)" \
+		"$(git rev-parse HEAD)" >>expect &&
+	git worktree list --porcelain -z >_actual &&
+	nul_to_q <_actual >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '"list" -z fails without --porcelain' '
+	test_must_fail git worktree list -z
+'
+
 test_expect_success '"list" all worktrees with locked annotation' '
 	test_when_finished "rm -rf locked unlocked out && git worktree prune" &&
 	git worktree add --detach locked main &&