Subject: Re: [PATCH v2 23/32] prune: strategies for linked checkouts

From: Marc Branchaud <[email-masked]>
Date: Mon, 22 Sep 2014 17:06:06 -0400

On 14-09-21 06:29 AM, Duy Nguyen wrote:
> Here we go again. Thanks both for the suggestions.

The documentation looks good to me.

FWIW:
Signed-off-by: Marc Branchaud <[email-masked]>

		M.

> -- 8< --
> Subject: [PATCH] prune: strategies for linked checkouts
> 
> (alias R=$GIT_COMMON_DIR/worktrees/<id>)
> 
>  - linked checkouts are supposed to keep its location in $R/gitdir up
>    to date. The use case is auto fixup after a manual checkout move.
> 
>  - linked checkouts are supposed to update mtime of $R/gitdir. If
>    $R/gitdir's mtime is older than a limit, and it points to nowhere,
>    worktrees/<id> is to be pruned.
> 
>  - If $R/locked exists, worktrees/<id> is not supposed to be pruned. If
>    $R/locked exists and $R/gitdir's mtime is older than a really long
>    limit, warn about old unused repo.
> 
>  - "git checkout --to" is supposed to make a hard link named $R/link
>    pointing to the .git file on supported file systems to help detect
>    the user manually deleting the checkout. If $R/link exists and its
>    link count is greated than 1, the repo is kept.
> 
> Helped-by: Marc Branchaud <[email-masked]>
> Helped-by: Eric Sunshine <[email-masked]>
> Signed-off-by: Nguyễn Thái Ngọc Duy <[email-masked]>
> ---
>  Documentation/git-checkout.txt             | 20 +++++++
>  Documentation/git-prune.txt                |  3 +
>  Documentation/gitrepository-layout.txt     | 19 ++++++
>  builtin/checkout.c                         | 19 +++++-
>  builtin/prune.c                            | 95 ++++++++++++++++++++++++++++++
>  setup.c                                    | 13 ++++
>  t/t2026-prune-linked-checkouts.sh (new +x) | 84 ++++++++++++++++++++++++++
>  7 files changed, 251 insertions(+), 2 deletions(-)
>  create mode 100755 t/t2026-prune-linked-checkouts.sh
> 
> diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
> index c101575..0fd3bab 100644
> --- a/Documentation/git-checkout.txt
> +++ b/Documentation/git-checkout.txt
> @@ -434,6 +434,26 @@ thumb is do not make any assumption about whether a path belongs to
>  $GIT_DIR or $GIT_COMMON_DIR when you need to directly access something
>  inside $GIT_DIR. Use `git rev-parse --git-path` to get the final path.
>  
> +When you are done with a linked working tree you can simply delete it.
> +You can clean up any stale $GIT_DIR/worktrees entries via `git prune
> +--worktrees` in the main worktree or any linked worktree.
> +
> +If you move a linked working directory to another file system, or
> +within a file system that does not support hard links, you need to run
> +at least one git command inside the linked working directory
> +(e.g. `git status`) in order to update its entry in $GIT_DIR/worktrees
> +so that it does not get automatically removed.
> +
> +To prevent `git prune --worktrees` from deleting a $GIT_DIR/worktrees
> +entry (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
> +'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
> +`/path/main/.git/worktrees/test-next/locked` will prevent the
> +`test-next` entry from being pruned.  See
> +linkgit:gitrepository-layout[5] for details.
> +
>  EXAMPLES
>  --------
>  
> diff --git a/Documentation/git-prune.txt b/Documentation/git-prune.txt
> index 7a493c8..a0ea381 100644
> --- a/Documentation/git-prune.txt
> +++ b/Documentation/git-prune.txt
> @@ -48,6 +48,9 @@ OPTIONS
>  --expire <time>::
>  	Only expire loose objects older than <time>.
>  
> +--worktrees::
> +	Prune stale worktree information in $GIT_DIR/worktrees.
> +
>  <head>...::
>  	In addition to objects
>  	reachable from any of our references, keep objects
> diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
> index 8228450..2b30a92 100644
> --- a/Documentation/gitrepository-layout.txt
> +++ b/Documentation/gitrepository-layout.txt
> @@ -259,6 +259,25 @@ worktrees::
>  	$GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/worktrees" will be
>  	used instead.
>  
> +worktrees/<id>/gitdir::
> +	A text file containing the absolute path back to the .git file
> +	that points to here. This is used to check if the linked
> +	repository has been manually removed and there is no need to
> +	keep this directory any more. mtime of this file should be
> +	updated every time the linked repository is accessed.
> +
> +worktrees/<id>/locked::
> +	If this file exists, the linked repository may be on a
> +	portable device and not available. It does not mean that the
> +	linked repository is gone and `worktrees/<id>` could be
> +	removed. The file's content contains a reason string on why
> +	the repository is locked.
> +
> +worktrees/<id>/link::
> +	If this file exists, it is a hard link to the linked .git
> +	file. It is used to detect if the linked repository is
> +	manually removed.
> +
>  SEE ALSO
>  --------
>  linkgit:git-init[1],
> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index ad10f99..ab46af9 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -826,7 +826,7 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
>  	const char *path = opts->new_worktree, *name;
>  	struct stat st;
>  	struct child_process cp;
> -	int counter = 0, len;
> +	int counter = 0, len, ret;
>  
>  	if (!new->commit)
>  		die(_("no branch specified"));
> @@ -857,11 +857,21 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
>  	if (mkdir(sb_repo.buf, 0777))
>  		die_errno(_("could not create directory of '%s'"), sb_repo.buf);
>  
> +	/*
> +	 * 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);
>  
> +	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);
>  	/*
> @@ -870,6 +880,7 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
>  	 * value would do because this value will be ignored and
>  	 * replaced at the next (real) checkout.
>  	 */
> +	strbuf_reset(&sb);
>  	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
>  	write_file(sb.buf, 1, "%s\n", sha1_to_hex(new->commit->object.sha1));
>  	strbuf_reset(&sb);
> @@ -885,7 +896,11 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
>  	memset(&cp, 0, sizeof(cp));
>  	cp.git_cmd = 1;
>  	cp.argv = opts->saved_argv;
> -	return run_command(&cp);
> +	ret = run_command(&cp);
> +	strbuf_reset(&sb);
> +	strbuf_addf(&sb, "%s/locked", sb_repo.buf);
> +	unlink_or_warn(sb.buf);
> +	return ret;
>  }
>  
>  static int git_checkout_config(const char *var, const char *value, void *cb)
> diff --git a/builtin/prune.c b/builtin/prune.c
> index 144a3bd..cf56110 100644
> --- a/builtin/prune.c
> +++ b/builtin/prune.c
> @@ -112,6 +112,91 @@ static void prune_object_dir(const char *path)
>  	}
>  }
>  
> +static int prune_worktree(const char *id, struct strbuf *reason)
> +{
> +	struct stat st;
> +	char *path;
> +	int fd, len;
> +
> +	if (!is_directory(git_path("worktrees/%s", id))) {
> +		strbuf_addf(reason, _("Removing worktrees/%s: not a valid directory"), id);
> +		return 1;
> +	}
> +	if (file_exists(git_path("worktrees/%s/locked", id)))
> +		return 0;
> +	if (stat(git_path("worktrees/%s/gitdir", id), &st)) {
> +		strbuf_addf(reason, _("Removing worktrees/%s: gitdir file does not exist"), id);
> +		return 1;
> +	}
> +	fd = open(git_path("worktrees/%s/gitdir", id), O_RDONLY);
> +	if (fd < 0) {
> +		strbuf_addf(reason, _("Removing worktrees/%s: unable to read gitdir file (%s)"),
> +			    id, strerror(errno));
> +		return 1;
> +	}
> +	len = st.st_size;
> +	path = xmalloc(len + 1);
> +	read_in_full(fd, path, len);
> +	close(fd);
> +	while (len && (path[len - 1] == '\n' || path[len - 1] == '\r'))
> +		len--;
> +	if (!len) {
> +		strbuf_addf(reason, _("Removing worktrees/%s: invalid gitdir file"), id);
> +		free(path);
> +		return 1;
> +	}
> +	path[len] = '\0';
> +	if (!file_exists(path)) {
> +		struct stat st_link;
> +		free(path);
> +		/*
> +		 * the repo is moved manually and has not been
> +		 * accessed since?
> +		 */
> +		if (!stat(git_path("worktrees/%s/link", id), &st_link) &&
> +		    st_link.st_nlink > 1)
> +			return 0;
> +		strbuf_addf(reason, _("Removing worktrees/%s: gitdir file points to non-existent location"), id);
> +		return 1;
> +	}
> +	free(path);
> +	return st.st_mtime <= expire;
> +}
> +
> +static void prune_worktrees(void)
> +{
> +	struct strbuf reason = STRBUF_INIT;
> +	struct strbuf path = STRBUF_INIT;
> +	DIR *dir = opendir(git_path("worktrees"));
> +	struct dirent *d;
> +	int ret;
> +	if (!dir)
> +		return;
> +	while ((d = readdir(dir)) != NULL) {
> +		if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
> +			continue;
> +		strbuf_reset(&reason);
> +		if (!prune_worktree(d->d_name, &reason))
> +			continue;
> +		if (show_only || verbose)
> +			printf("%s\n", reason.buf);
> +		if (show_only)
> +			continue;
> +		strbuf_reset(&path);
> +		strbuf_addstr(&path, git_path("worktrees/%s", d->d_name));
> +		ret = remove_dir_recursively(&path, 0);
> +		if (ret < 0 && errno == ENOTDIR)
> +			ret = unlink(path.buf);
> +		if (ret)
> +			error(_("failed to remove: %s"), strerror(errno));
> +	}
> +	closedir(dir);
> +	if (!show_only)
> +		rmdir(git_path("worktrees"));
> +	strbuf_release(&reason);
> +	strbuf_release(&path);
> +}
> +
>  /*
>   * Write errors (particularly out of space) can result in
>   * failed temporary packs (and more rarely indexes and other
> @@ -138,10 +223,12 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
>  {
>  	struct rev_info revs;
>  	struct progress *progress = NULL;
> +	int do_prune_worktrees = 0;
>  	const struct option options[] = {
>  		OPT__DRY_RUN(&show_only, N_("do not remove, show only")),
>  		OPT__VERBOSE(&verbose, N_("report pruned objects")),
>  		OPT_BOOL(0, "progress", &show_progress, N_("show progress")),
> +		OPT_BOOL(0, "worktrees", &do_prune_worktrees, N_("prune .git/worktrees")),
>  		OPT_EXPIRY_DATE(0, "expire", &expire,
>  				N_("expire objects older than <time>")),
>  		OPT_END()
> @@ -154,6 +241,14 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
>  	init_revisions(&revs, prefix);
>  
>  	argc = parse_options(argc, argv, prefix, options, prune_usage, 0);
> +
> +	if (do_prune_worktrees) {
> +		if (argc)
> +			die(_("--worktrees does not take extra arguments"));
> +		prune_worktrees();
> +		return 0;
> +	}
> +
>  	while (argc--) {
>  		unsigned char sha1[20];
>  		const char *name = *argv++;
> diff --git a/setup.c b/setup.c
> index b99bdd3..fb61860 100644
> --- a/setup.c
> +++ b/setup.c
> @@ -390,6 +390,17 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
>  	return ret;
>  }
>  
> +static void update_linked_gitdir(const char *gitfile, const char *gitdir)
> +{
> +	struct strbuf path = STRBUF_INIT;
> +	struct stat st;
> +
> +	strbuf_addf(&path, "%s/gitfile", gitdir);
> +	if (stat(path.buf, &st) || st.st_mtime + 24 * 3600 < time(NULL))
> +		write_file(path.buf, 0, "%s\n", gitfile);
> +	strbuf_release(&path);
> +}
> +
>  /*
>   * Try to read the location of the git directory from the .git file,
>   * return path to git directory if found.
> @@ -438,6 +449,8 @@ const char *read_gitfile(const char *path)
>  
>  	if (!is_git_directory(dir))
>  		die("Not a git repository: %s", dir);
> +
> +	update_linked_gitdir(path, dir);
>  	path = real_path(dir);
>  
>  	free(buf);
> diff --git a/t/t2026-prune-linked-checkouts.sh b/t/t2026-prune-linked-checkouts.sh
> new file mode 100755
> index 0000000..3622800
> --- /dev/null
> +++ b/t/t2026-prune-linked-checkouts.sh
> @@ -0,0 +1,84 @@
> +#!/bin/sh
> +
> +test_description='prune $GIT_DIR/worktrees'
> +
> +. ./test-lib.sh
> +
> +test_expect_success 'prune --worktrees on normal repo' '
> +	git prune --worktrees &&
> +	test_must_fail git prune --worktrees abc
> +'
> +
> +test_expect_success 'prune files inside $GIT_DIR/worktrees' '
> +	mkdir .git/worktrees &&
> +	: >.git/worktrees/abc &&
> +	git prune --worktrees --verbose >actual &&
> +	cat >expect <<EOF &&
> +Removing worktrees/abc: not a valid directory
> +EOF
> +	test_i18ncmp expect actual &&
> +	! test -f .git/worktrees/abc &&
> +	! test -d .git/worktrees
> +'
> +
> +test_expect_success 'prune directories without gitdir' '
> +	mkdir -p .git/worktrees/def/abc &&
> +	: >.git/worktrees/def/def &&
> +	cat >expect <<EOF &&
> +Removing worktrees/def: gitdir file does not exist
> +EOF
> +	git prune --worktrees --verbose >actual &&
> +	test_i18ncmp expect actual &&
> +	! test -d .git/worktrees/def &&
> +	! test -d .git/worktrees
> +'
> +
> +test_expect_success POSIXPERM 'prune directories with unreadable gitdir' '
> +	mkdir -p .git/worktrees/def/abc &&
> +	: >.git/worktrees/def/def &&
> +	: >.git/worktrees/def/gitdir &&
> +	chmod u-r .git/worktrees/def/gitdir &&
> +	git prune --worktrees --verbose >actual &&
> +	test_i18ngrep "Removing worktrees/def: unable to read gitdir file" actual &&
> +	! test -d .git/worktrees/def &&
> +	! test -d .git/worktrees
> +'
> +
> +test_expect_success 'prune directories with invalid gitdir' '
> +	mkdir -p .git/worktrees/def/abc &&
> +	: >.git/worktrees/def/def &&
> +	: >.git/worktrees/def/gitdir &&
> +	git prune --worktrees --verbose >actual &&
> +	test_i18ngrep "Removing worktrees/def: invalid gitdir file" actual &&
> +	! test -d .git/worktrees/def &&
> +	! test -d .git/worktrees
> +'
> +
> +test_expect_success 'prune directories with gitdir pointing to nowhere' '
> +	mkdir -p .git/worktrees/def/abc &&
> +	: >.git/worktrees/def/def &&
> +	echo "$TRASH_DIRECTORY"/nowhere >.git/worktrees/def/gitdir &&
> +	git prune --worktrees --verbose >actual &&
> +	test_i18ngrep "Removing worktrees/def: gitdir file points to non-existent location" actual &&
> +	! test -d .git/worktrees/def &&
> +	! test -d .git/worktrees
> +'
> +
> +test_expect_success 'not prune locked checkout' '
> +	test_when_finished rm -r .git/worktrees
> +	mkdir -p .git/worktrees/ghi &&
> +	: >.git/worktrees/ghi/locked &&
> +	git prune --worktrees &&
> +	test -d .git/worktrees/ghi
> +'
> +
> +test_expect_success 'not prune recent checkouts' '
> +	test_when_finished rm -r .git/worktrees
> +	mkdir zz &&
> +	mkdir -p .git/worktrees/jlm &&
> +	echo "$TRASH_DIRECTORY"/zz >.git/worktrees/jlm/gitdir &&
> +	git prune --worktrees --verbose --expire=2.days.ago &&
> +	test -d .git/worktrees/jlm
> +'
> +
> +test_done
>