[PATCH v5 0/6] builtin/maintenance: implement missing tasks compared to git-gc(1)

[Patrick Steinhardt <ps@pks.im>]

Hi,

this small patch series implements the last couple of remaining tasks
that are missing compared to the functionality git-gc(1) provides.

Right now, git-maintenance(1) still executes git-gc(1). With these last
gaps plugged though we can in theory fully replace git-gc(1) with finer
grained tasks without losing any functionality. The benefit is that it
becomes possible for users to have finer-grained control over what
exactly the maintenance does.

This patch series doesn't do that yet, but only implements whatever is
needed to get there.

Changes in v2:
  - Introduce "maintenance.worktree-prune.auto", which controls how many
    stale worktrees need to exist before executing `git worktree prune`.
  - Introduce "maintenance.rerere-gc.auto", which controls how many
    stale rerere entries need to exist before executing `git rerere gc`.
  - Add tests to verify that "gc.worktreePruneExpire" works.
  - Remove some fragile test logic by introducing functions that check
    for a given maintenance subprocess.
  - Link to v1: https://lore.kernel.org/r/20250425-pks-maintenance-missing-tasks-v1-0-972ed6ab2c0d@pks.im

Changes in v3:
  - Simplify the heuristic for "rerere-gc" so that we only count the
    number of directory entries in ".git/rr-cache", without considering
    staleness.
  - Link to v2: https://lore.kernel.org/r/20250430-pks-maintenance-missing-tasks-v2-0-2580b7b8ca3a@pks.im

Changes in v4:
  - simplified the heuristic for "rerere-gc" even further. A positive
    value for "maintenance.rerere-gc.auto" now indicates that the
    command will run whenever there is at least one directory entry in
    ".rr-cache". The exact value does not matter anymore.
  - Link to v3: https://lore.kernel.org/r/20250502-pks-maintenance-missing-tasks-v3-0-13e130d36640@pks.im

Changes in v5:
  - Drop `get_worktree_names()` in favor of an open-coded loop.
  - Fix a memory leak.
  - Simplified the logic in `worktree_prune_condition()` a bit.
  - Link to v4: https://lore.kernel.org/r/20250505-pks-maintenance-missing-tasks-v4-0-141f4df906a1@pks.im

Thanks!

Patrick

---
Patrick Steinhardt (6):
      builtin/gc: fix indentation of `cmd_gc()` parameters
      builtin/gc: remove global variables where it is trivial to do
      builtin/gc: move pruning of worktrees into a separate function
      builtin/maintenance: introduce "worktree-prune" task
      builtin/gc: move rerere garbage collection into separate function
      builtin/maintenance: introduce "rerere-gc" task

 Documentation/config/maintenance.adoc |  17 ++++
 Documentation/git-maintenance.adoc    |   8 ++
 builtin/gc.c                          | 148 +++++++++++++++++++++++++++-------
 t/t7900-maintenance.sh                | 115 ++++++++++++++++++++++++++
 4 files changed, 257 insertions(+), 31 deletions(-)

Range-diff versus v4:

1:  59edf54e3ec = 1:  815904a68a1 builtin/gc: fix indentation of `cmd_gc()` parameters
2:  9f02c33f5b9 ! 2:  91f4c304232 builtin/gc: remove global variables where it trivial to do
    @@ Metadata
     Author: Patrick Steinhardt <ps@pks.im>
     
      ## Commit message ##
    -    builtin/gc: remove global variables where it trivial to do
    +    builtin/gc: remove global variables where it is trivial to do
     
         We use a couple of global variables to assemble command line arguments
         for subprocesses we execute in git-gc(1). All of these variables except
3:  b280af7bbc4 ! 3:  9232c8aac1d builtin/gc: move pruning of worktrees into a separate function
    @@ Metadata
      ## Commit message ##
         builtin/gc: move pruning of worktrees into a separate function
     
    -    Move pruning of worktrees into a separate function. This prepares for a
    -    subsequent commit where we introduce a new "worktree-prune" task for
    -    git-maintenance(1).
    +    In a subsequent commit we will introduce a new "worktree-prune" task for
    +    git-maintenance(1). To prepare for this, refactor the code that spawns
    +    `git worktree prune` into a separate function.
     
         Signed-off-by: Patrick Steinhardt <ps@pks.im>
     
4:  58ce12459c2 < -:  ----------- worktree: expose function to retrieve worktree names
5:  efeec465db0 ! 4:  24ca70b35b9 builtin/maintenance: introduce "worktree-prune" task
    @@ builtin/gc.c: static int maintenance_task_worktree_prune(struct maintenance_run_
      
     +static int worktree_prune_condition(struct gc_config *cfg)
     +{
    -+	struct strvec worktrees = STRVEC_INIT;
    -+	struct strbuf reason = STRBUF_INIT;
    ++	struct strbuf buf = STRBUF_INIT;
    ++	int should_prune = 0, limit = 1;
     +	timestamp_t expiry_date;
    -+	int should_prune = 0;
    -+	int limit = 1;
    ++	struct dirent *d;
    ++	DIR *dir = NULL;
     +
     +	git_config_get_int("maintenance.worktree-prune.auto", &limit);
     +	if (limit <= 0) {
    @@ builtin/gc.c: static int maintenance_task_worktree_prune(struct maintenance_run_
     +		goto out;
     +	}
     +
    -+	if (parse_expiry_date(cfg->prune_worktrees_expire, &expiry_date) ||
    -+	    get_worktree_names(the_repository, &worktrees) < 0)
    ++	if (parse_expiry_date(cfg->prune_worktrees_expire, &expiry_date))
     +		goto out;
     +
    -+	for (size_t i = 0; i < worktrees.nr; i++) {
    -+		char *wtpath;
    ++	dir = opendir(repo_git_path_replace(the_repository, &buf, "worktrees"));
    ++	if (!dir)
    ++		goto out;
     +
    -+		strbuf_reset(&reason);
    -+		if (should_prune_worktree(worktrees.v[i], &reason, &wtpath, expiry_date)) {
    ++	while (limit && (d = readdir_skip_dot_and_dotdot(dir))) {
    ++		char *wtpath;
    ++		strbuf_reset(&buf);
    ++		if (should_prune_worktree(d->d_name, &buf, &wtpath, expiry_date))
     +			limit--;
    -+
    -+			if (!limit) {
    -+				should_prune = 1;
    -+				goto out;
    -+			}
    -+		}
     +		free(wtpath);
     +	}
     +
    ++	should_prune = !limit;
    ++
     +out:
    -+	strvec_clear(&worktrees);
    -+	strbuf_release(&reason);
    ++	if (dir)
    ++		closedir(dir);
    ++	strbuf_release(&buf);
     +	return should_prune;
     +}
     +
    @@ t/t7900-maintenance.sh: test_expect_success 'reflog-expire task --auto only pack
     +
     +	# Zero should never prune.
     +	test_expect_worktree_prune ! git -c maintenance.worktree-prune.auto=0 maintenance run --auto --task=worktree-prune &&
    -+	# A positive value should require at least this man prunable worktrees.
    ++	# A positive value should require at least this many prunable worktrees.
     +	test_expect_worktree_prune ! git -c maintenance.worktree-prune.auto=4 maintenance run --auto --task=worktree-prune &&
     +	test_expect_worktree_prune git -c maintenance.worktree-prune.auto=3 maintenance run --auto --task=worktree-prune
     +'
6:  10ed12cc737 ! 5:  67e05501fbb builtin/gc: move rerere garbage collection into separate function
    @@ Metadata
      ## Commit message ##
         builtin/gc: move rerere garbage collection into separate function
     
    -    Move garbage collection of cached rerere entries into a separate
    -    function. This prepares us for a subsequent commit where we introduce a
    -    new "rerere-gc" task for git-maintenance(1).
    +    In a subsequent commit we are going to introduce a new "rerere-gc" task
    +    for git-maintenance(1). To prepare for this, refactor the code that
    +    spawns `git rerere gc` into a separate function.
     
         Signed-off-by: Patrick Steinhardt <ps@pks.im>
     
7:  be7fa13115c = 6:  818ed6b8999 builtin/maintenance: introduce "rerere-gc" task

---
base-commit: a2955b34f48265d240ab8c7deb0a929ec2d65fd0
change-id: 20250424-pks-maintenance-missing-tasks-8ffcdd596b73