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> -- 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 <marcnarc@xiplink.com>
> Helped-by: Eric Sunshine <sunshine@sunshineco.com>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
> 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
> Marc Branchaud <marcnarc@xiplink.com>