checkout: retire --to option

Now that "git worktree add" has achieved user-facing feature-parity with
"git checkout --to", retire the latter.

Move the actual linked worktree creation functionality,
prepare_linked_checkout() and its helpers, verbatim from checkout.c to
worktree.c.

This effectively reverts changes to checkout.c by 529fef2 (checkout:
support checking out into a new working directory, 2014-11-30) with the
exception of merge_working_tree() and switch_branches() which still
require specialized knowledge that a the checkout is occurring in a
newly-created linked worktree (signaled to them by the private
GIT_CHECKOUT_NEW_WORKTREE environment variable).

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 138 insertions, 6 deletions

diff --git a/builtin/worktree.c b/builtin/worktree.c
index d6d0eee3c..04e6d0f92 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -4,6 +4,7 @@
 #include "parse-options.h"
 #include "argv-array.h"
 #include "run-command.h"
+#include "sigchain.h"
 
 static const char * const worktree_usage[] = {
 	N_("git worktree add [<options>] <path> <branch>"),
@@ -122,9 +123,144 @@ static int prune(int ac, const char **av, const char *prefix)
 	return 0;
 }
 
+static char *junk_work_tree;
+static char *junk_git_dir;
+static int is_junk;
+static pid_t junk_pid;
+
+static void remove_junk(void)
+{
+	struct strbuf sb = STRBUF_INIT;
+	if (!is_junk || getpid() != junk_pid)
+		return;
+	if (junk_git_dir) {
+		strbuf_addstr(&sb, junk_git_dir);
+		remove_dir_recursively(&sb, 0);
+		strbuf_reset(&sb);
+	}
+	if (junk_work_tree) {
+		strbuf_addstr(&sb, junk_work_tree);
+		remove_dir_recursively(&sb, 0);
+	}
+	strbuf_release(&sb);
+}
+
+static void remove_junk_on_signal(int signo)
+{
+	remove_junk();
+	sigchain_pop(signo);
+	raise(signo);
+}
+
+static int add_worktree(const char *path, const char **child_argv)
+{
+	struct strbuf sb_git = STRBUF_INIT, sb_repo = STRBUF_INIT;
+	struct strbuf sb = STRBUF_INIT;
+	const char *name;
+	struct stat st;
+	struct child_process cp;
+	int counter = 0, len, ret;
+	unsigned char rev[20];
+
+	if (file_exists(path) && !is_empty_dir(path))
+		die(_("'%s' already exists"), path);
+
+	len = strlen(path);
+	while (len && is_dir_sep(path[len - 1]))
+		len--;
+
+	for (name = path + len - 1; name > path; name--)
+		if (is_dir_sep(*name)) {
+			name++;
+			break;
+		}
+	strbuf_addstr(&sb_repo,
+		      git_path("worktrees/%.*s", (int)(path + len - name), name));
+	len = sb_repo.len;
+	if (safe_create_leading_directories_const(sb_repo.buf))
+		die_errno(_("could not create leading directories of '%s'"),
+			  sb_repo.buf);
+	while (!stat(sb_repo.buf, &st)) {
+		counter++;
+		strbuf_setlen(&sb_repo, len);
+		strbuf_addf(&sb_repo, "%d", counter);
+	}
+	name = strrchr(sb_repo.buf, '/') + 1;
+
+	junk_pid = getpid();
+	atexit(remove_junk);
+	sigchain_push_common(remove_junk_on_signal);
+
+	if (mkdir(sb_repo.buf, 0777))
+		die_errno(_("could not create directory of '%s'"), sb_repo.buf);
+	junk_git_dir = xstrdup(sb_repo.buf);
+	is_junk = 1;
+
+	/*
+	 * lock the incomplete repo so prune won't delete it, unlock
+	 * after the preparation is over.
+	 */
+	strbuf_addf(&sb, "%s/locked", sb_repo.buf);
+	write_file(sb.buf, 1, "initializing\n");
+
+	strbuf_addf(&sb_git, "%s/.git", path);
+	if (safe_create_leading_directories_const(sb_git.buf))
+		die_errno(_("could not create leading directories of '%s'"),
+			  sb_git.buf);
+	junk_work_tree = xstrdup(path);
+
+	strbuf_reset(&sb);
+	strbuf_addf(&sb, "%s/gitdir", sb_repo.buf);
+	write_file(sb.buf, 1, "%s\n", real_path(sb_git.buf));
+	write_file(sb_git.buf, 1, "gitdir: %s/worktrees/%s\n",
+		   real_path(get_git_common_dir()), name);
+	/*
+	 * This is to keep resolve_ref() happy. We need a valid HEAD
+	 * or is_git_directory() will reject the directory. Moreover, HEAD
+	 * in the new worktree must resolve to the same value as HEAD in
+	 * the current tree since the command invoked to populate the new
+	 * worktree will be handed the branch/ref specified by the user.
+	 * For instance, if the user asks for the new worktree to be based
+	 * at HEAD~5, then the resolved HEAD~5 in the new worktree must
+	 * match the resolved HEAD~5 in the current tree in order to match
+	 * the user's expectation.
+	 */
+	if (!resolve_ref_unsafe("HEAD", 0, rev, NULL))
+		die(_("unable to resolve HEAD"));
+	strbuf_reset(&sb);
+	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
+	write_file(sb.buf, 1, "%s\n", sha1_to_hex(rev));
+	strbuf_reset(&sb);
+	strbuf_addf(&sb, "%s/commondir", sb_repo.buf);
+	write_file(sb.buf, 1, "../..\n");
+
+	fprintf_ln(stderr, _("Enter %s (identifier %s)"), path, name);
+
+	setenv("GIT_CHECKOUT_NEW_WORKTREE", "1", 1);
+	setenv(GIT_DIR_ENVIRONMENT, sb_git.buf, 1);
+	setenv(GIT_WORK_TREE_ENVIRONMENT, path, 1);
+	memset(&cp, 0, sizeof(cp));
+	cp.git_cmd = 1;
+	cp.argv = child_argv;
+	ret = run_command(&cp);
+	if (!ret) {
+		is_junk = 0;
+		free(junk_work_tree);
+		free(junk_git_dir);
+		junk_work_tree = NULL;
+		junk_git_dir = NULL;
+	}
+	strbuf_reset(&sb);
+	strbuf_addf(&sb, "%s/locked", sb_repo.buf);
+	unlink_or_warn(sb.buf);
+	strbuf_release(&sb);
+	strbuf_release(&sb_repo);
+	strbuf_release(&sb_git);
+	return ret;
+}
+
 static int add(int ac, const char **av, const char *prefix)
 {
-	struct child_process c;
 	int force = 0, detach = 0;
 	const char *new_branch = NULL, *new_branch_force = NULL;
 	const char *path, *branch;
@@ -149,7 +285,6 @@ static int add(int ac, const char **av, const char *prefix)
 	branch = av[1];
 
 	argv_array_push(&cmd, "checkout");
-	argv_array_pushl(&cmd, "--to", path, NULL);
 	if (force)
 		argv_array_push(&cmd, "--ignore-other-worktrees");
 	if (new_branch)
@@ -160,10 +295,7 @@ static int add(int ac, const char **av, const char *prefix)
 		argv_array_push(&cmd, "--detach");
 	argv_array_push(&cmd, branch);
 
-	memset(&c, 0, sizeof(c));
-	c.git_cmd = 1;
-	c.argv = cmd.argv;
-	return run_command(&c);
+	return add_worktree(path, cmd.argv);
 }
 
 int cmd_worktree(int ac, const char **av, const char *prefix)