[PATCH v2 0/6] worktree: initialize refdb via ref backends

Hi,

this is the second version of my patch series that refactors the initialization of worktree refdbs to use the refs API.

Changes compared to v1:

  - Improved commit messages.

  - This series is now based on `ps/refstorage-extension`, 1b2234079b
    (t9500: write "extensions.refstorage" into config, 2023-12-29).
    While there is no functional dependency between those series,
    merging both topics causes a merge conflict.

Patrick

Patrick Steinhardt (6):
  refs: prepare `refs_init_db()` for initializing worktree refs
  setup: move creation of "refs/" into the files backend
  refs/files: skip creation of "refs/{heads,tags}" for worktrees
  builtin/worktree: move setup of commondir file earlier
  worktree: expose interface to look up worktree by name
  builtin/worktree: create refdb via ref backend

 builtin/worktree.c    | 53 ++++++++++++++++++++-----------------------
 refs.c                |  6 ++---
 refs.h                |  4 +++-
 refs/debug.c          |  4 ++--
 refs/files-backend.c  | 37 +++++++++++++++++++++++++-----
 refs/packed-backend.c |  1 +
 refs/refs-internal.h  |  4 +++-
 setup.c               | 17 +-------------
 worktree.c            | 27 +++++++++++++---------
 worktree.h            | 12 ++++++++++
 10 files changed, 96 insertions(+), 69 deletions(-)

Range-diff against v1:
1:  6cb4e0a99f ! 1:  a4894b3e15 refs: prepare `refs_init_db()` for initializing worktree refs
    @@ refs/refs-internal.h: typedef struct ref_store *ref_store_init_fn(struct reposit
      				       struct ref_transaction *transaction,
     
      ## setup.c ##
    -@@ setup.c: void create_reference_database(const char *initial_branch, int quiet)
    - 	safe_create_dir(git_path("refs"), 1);
    +@@ setup.c: void create_reference_database(unsigned int ref_storage_format,
      	adjust_shared_perm(git_path("refs"));
      
    + 	repo_set_ref_storage_format(the_repository, ref_storage_format);
     -	if (refs_init_db(&err))
     +	if (refs_init_db(get_main_ref_store(the_repository), 0, &err))
      		die("failed to set up refs db: %s", err.buf);
2:  ae013eaa4a ! 2:  f500db51c2 setup: move creation of "refs/" into the files backend
    @@ Commit message
         seems a lot more sensible to have it this way round than to require
         callers to create the directory themselves.
     
    +    An alternative to this would be to create "refs/" in `refs_init_db()`
    +    directly. This feels conceptually unclean though as the creation of the
    +    refdb is now cluttered across different callsites. Furthermore, both the
    +    "files" and the upcoming "reftable" backend write backend-specific data
    +    into the "refs/" directory anyway, so splitting up this logic would only
    +    make it harder to reason about.
    +
         Signed-off-by: Patrick Steinhardt <ps@pks.im>
     
      ## refs/files-backend.c ##
    @@ refs/files-backend.c: static int files_init_db(struct ref_store *ref_store,
      
     
      ## setup.c ##
    -@@ setup.c: void create_reference_database(const char *initial_branch, int quiet)
    +@@ setup.c: void create_reference_database(unsigned int ref_storage_format,
      	struct strbuf err = STRBUF_INIT;
      	int reinit = is_reinit();
      
    @@ setup.c: void create_reference_database(const char *initial_branch, int quiet)
     -	safe_create_dir(git_path("refs"), 1);
     -	adjust_shared_perm(git_path("refs"));
     -
    + 	repo_set_ref_storage_format(the_repository, ref_storage_format);
      	if (refs_init_db(get_main_ref_store(the_repository), 0, &err))
      		die("failed to set up refs db: %s", err.buf);
    - 
3:  3cf6ceb274 ! 3:  9e99efeaa3 refs/files: skip creation of "refs/{heads,tags}" for worktrees
    @@ Commit message
     
         The files ref backend will create both "refs/heads" and "refs/tags" in
         the Git directory. While this logic makes sense for normal repositories,
    -    it does not fo worktrees because those refs are "common" refs that would
    -    always be contained in the main repository's ref database.
    +    it does not for worktrees because those refs are "common" refs that
    +    would always be contained in the main repository's ref database.
     
         Introduce a new flag telling the backend that it is expected to create a
         per-worktree ref database and skip creation of these dirs in the files
4:  1a6337fc51 = 4:  f2eb020288 builtin/worktree: move setup of commondir file earlier
5:  f344a915e9 ! 5:  5525a9f9c2 worktree: expose interface to look up worktree by name
    @@ worktree.c
      	free (worktrees);
      }
      
    -@@ worktree.c: static struct worktree *get_main_worktree(void)
    +@@ worktree.c: static struct worktree *get_main_worktree(int skip_reading_head)
      	return worktree;
      }
      
    --static struct worktree *get_linked_worktree(const char *id)
    -+struct worktree *get_linked_worktree(const char *id)
    +-static struct worktree *get_linked_worktree(const char *id,
    +-					    int skip_reading_head)
    ++struct worktree *get_linked_worktree(const char *id,
    ++				     int skip_reading_head)
      {
      	struct worktree *worktree = NULL;
      	struct strbuf path = STRBUF_INIT;
    @@ worktree.h: struct worktree *find_worktree(struct worktree **list,
     + * Look up the worktree corresponding to `id`, or NULL of no such worktree
     + * exists.
     + */
    -+struct worktree *get_linked_worktree(const char *id);
    ++struct worktree *get_linked_worktree(const char *id,
    ++				     int skip_reading_head);
     +
      /*
       * Return the worktree corresponding to `path`, or NULL if no such worktree
6:  aae969301f ! 6:  240dc40de1 builtin/worktree: create refdb via ref backend
    @@ builtin/worktree.c: static int add_worktree(const char *path, const char *refnam
     -	strbuf_reset(&sb);
     -	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
     -	write_file(sb.buf, "%s", oid_to_hex(null_oid()));
    -+	wt = get_linked_worktree(name);
    ++	wt = get_linked_worktree(name, 1);
     +	if (!wt) {
     +		ret = error(_("could not find created worktree '%s'"), name);
     +		goto done;

base-commit: 1b2234079b24da99dd78e4ce4bfe338a2a841aed