[PATCH 0/8] setup: centralize object database creation

[PATCH 0/8] setup: centralize object database creation

[Patrick Steinhardt]

Hi,

this small patch series refactors the logic for how we discover and
configure repositories. Most importantly, this involves the following
two steps:

  1. We unify the logic to apply the repository format, which is
     currently open-coded across multiple sites. These sites have
     already diverged, where some repository extensions are not
     consistently applied.

  2. We then centralize creation of the object database to happen at the
     same time we apply the repository format.

The end result is that we apply the repository format exactly once, and
that's also the point in time where we can finalize the setup of the
repo's data structures as we know about all details of the repo at that
time. Ultimately, this makes it trivial to introduce the "objectStorage"
extension, even though that's not part of this patch series.

The series is built on top of aec3f58750 (Sync with 'maint', 2026-05-21)
with ps/setup-wo-the-repository at df69f40c34 (setup: stop using
`the_repository` in `init_db()`, 2026-05-19) merged into it.

Thanks!

Patrick

---
Patrick Steinhardt (8):
      t0001: plug test gaps for git-init(1) with GIT_OBJECT_DIRECTORY
      setup: drop `setup_git_env()`
      setup: deduplicate logic to apply repository format
      repository: stop initializing the object database in `repo_set_gitdir()`
      setup: stop creating the object database in `setup_git_env()`
      setup: stop initializing object database without repository
      repository: stop reading loose object map twice on repo init
      setup: construct object database in `apply_repository_format()`

 commit-graph.c  |   4 +-
 environment.h   |   8 +---
 refs.c          |   3 +-
 repository.c    |  40 +++++------------
 repository.h    |   3 --
 setup.c         | 130 +++++++++++++++++++++++++++++++-------------------------
 setup.h         |  19 +++++++++
 t/t0001-init.sh |  10 +++++
 8 files changed, 117 insertions(+), 100 deletions(-)


---
base-commit: 3398daa441965513c48744305d33bd36404547d6
change-id: 20260519-b4-pks-setup-centralize-odb-creation-3479c53fb11d

[PATCH 1/8] t0001: plug test gaps for git-init(1) with GIT_OBJECT_DIRECTORY

[Patrick Steinhardt]

In subsequent commits we'll rework how we set up the repository. This is
a somewhat intricate and thus fragile sequence, there's many things that
can go subtly wrong, and there are lots of interesting interactions that
one can discover.

One such discovered edge case was the interaction between git-init(1)
and the "GIT_OBJECT_DIRECTORY" enviroment variable. When set, the
behaviour is that the object directory should be created at the path
that the variable points to. This behaviour is documented as such in
its man page:

  If the object storage directory is specified via the
  GIT_OBJECT_DIRECTORY environment variable then the sha1 directories
  are created underneath; otherwise, the default $GIT_DIR/objects
  directory is used.

Curiously enough though we don't seem to have any tests that exercise
this directly, and thus a subsequent commit inadvertently broke this
expectation.

Plug this test gap.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 t/t0001-init.sh | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/t/t0001-init.sh b/t/t0001-init.sh
index e4d32bb4d2..e89feca544 100755
--- a/t/t0001-init.sh
+++ b/t/t0001-init.sh
@@ -980,4 +980,14 @@ test_expect_success 're-init reads matching includeIf.onbranch' '
 	test_cmp expect err
 '
 
+test_expect_success 'init honors GIT_OBJECT_DIRECTORY' '
+	test_when_finished "rm -rf init-objdir custom-odb" &&
+	mkdir custom-odb &&
+	env GIT_OBJECT_DIRECTORY="$(pwd)/custom-odb" \
+		git init init-objdir &&
+	test_path_is_missing init-objdir/.git/objects/pack &&
+	test_path_is_dir custom-odb/pack &&
+	test_path_is_dir custom-odb/info
+'
+
 test_done

-- 
2.54.0.771.g3ed373ac14.dirty

Re: [PATCH 1/8] t0001: plug test gaps for git-init(1) with GIT_OBJECT_DIRECTORY

[Junio C Hamano]

Patrick Steinhardt <ps@pks.im> writes:

> In subsequent commits we'll rework how we set up the repository. This is
> a somewhat intricate and thus fragile sequence, there's many things that
> can go subtly wrong, and there are lots of interesting interactions that
> one can discover.
>
> One such discovered edge case was the interaction between git-init(1)
> and the "GIT_OBJECT_DIRECTORY" enviroment variable. When set, the

"environment"???

> behaviour is that the object directory should be created at the path
> that the variable points to. This behaviour is documented as such in
> its man page:
>
>   If the object storage directory is specified via the
>   GIT_OBJECT_DIRECTORY environment variable then the sha1 directories
>   are created underneath; otherwise, the default $GIT_DIR/objects
>   directory is used.
>
> Curiously enough though we don't seem to have any tests that exercise
> this directly, and thus a subsequent commit inadvertently broke this
> expectation.
>
> Plug this test gap.

Nice.

> Signed-off-by: Patrick Steinhardt <ps@pks.im>
> ---
>  t/t0001-init.sh | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/t/t0001-init.sh b/t/t0001-init.sh
> index e4d32bb4d2..e89feca544 100755
> --- a/t/t0001-init.sh
> +++ b/t/t0001-init.sh
> @@ -980,4 +980,14 @@ test_expect_success 're-init reads matching includeIf.onbranch' '
>  	test_cmp expect err
>  '
>  
> +test_expect_success 'init honors GIT_OBJECT_DIRECTORY' '
> +	test_when_finished "rm -rf init-objdir custom-odb" &&
> +	mkdir custom-odb &&
> +	env GIT_OBJECT_DIRECTORY="$(pwd)/custom-odb" \
> +		git init init-objdir &&
> +	test_path_is_missing init-objdir/.git/objects/pack &&
> +	test_path_is_dir custom-odb/pack &&
> +	test_path_is_dir custom-odb/info
> +'
> +
>  test_done

Re: [PATCH 1/8] t0001: plug test gaps for git-init(1) with GIT_OBJECT_DIRECTORY

[Kristoffer Haugsbakk]

On Thu, May 21, 2026, at 09:42, Patrick Steinhardt wrote:
> In subsequent commits we'll rework how we set up the repository. This is
> a somewhat intricate and thus fragile sequence, there's many things that

Should this be s/, there/; there/ ? Depends on if this is a list of
three items or if “This is” is a subclause that is supposed to point at
“there's many”.

> can go subtly wrong, and there are lots of interesting interactions that
> one can discover.
>
> One such discovered edge case was the interaction between git-init(1)
> and the "GIT_OBJECT_DIRECTORY" enviroment variable. When set, the
> behaviour is that the object directory should be created at the path
> that the variable points to. This behaviour is documented as such in
> its man page:
>
>   If the object storage directory is specified via the
>   GIT_OBJECT_DIRECTORY environment variable then the sha1 directories
>   are created underneath; otherwise, the default $GIT_DIR/objects
>   directory is used.
>
> Curiously enough though we don't seem to have any tests that exercise
> this directly, and thus a subsequent commit inadvertently broke this
> expectation.

Isn’t it more that “the upcoming changes *would have* broken” them if
not for this change? This seems to refer to a an alternative commit
history where this change does not exist?

>
> Plug this test gap.
>
> Signed-off-by: Patrick Steinhardt <ps@pks.im>
> ---
>[snip]

[PATCH 2/8] setup: drop `setup_git_env()`

[Patrick Steinhardt]

The `setup_git_env()` function is a trivial wrapper around
`setup_git_env_internal()` and has a single call site only. Drop the
function.

While at it, drop stale documentation in "environment.h" that points to
this function, even though it hasn't been exposed to callers outside of
"setup.c" since 43ad1047a9 (setup: stop using `the_repository` in
`setup_git_env()`, 2026-03-27) anymore.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 environment.h | 8 +-------
 refs.c        | 3 ++-
 setup.c       | 7 +------
 3 files changed, 4 insertions(+), 14 deletions(-)

diff --git a/environment.h b/environment.h
index 9eb97b3869..ccfcf37bfb 100644
--- a/environment.h
+++ b/environment.h
@@ -130,13 +130,6 @@ void repo_config_values_init(struct repo_config_values *cfg);
  * `the_repository`. We should eventually get rid of these and make the
  * dependency on a repository explicit:
  *
- *   - `setup_git_env()` ideally shouldn't exist as it modifies global state,
- *     namely the environment. The current process shouldn't ever access that
- *     state via envvars though, but should instead consult a `struct
- *     repository`. When spawning new processes, we would ideally also pass a
- *     `struct repository` and then set up the environment variables for the
- *     child process, only.
- *
  *   - `have_git_dir()` should not have to exist at all. Instead, we should
  *     decide on whether or not we have a `struct repository`.
  *
@@ -147,6 +140,7 @@ void repo_config_values_init(struct repo_config_values *cfg);
  * Please do not add new global config variables here.
  */
 # ifdef USE_THE_REPOSITORY_VARIABLE
+
 /*
  * Returns true iff we have a configured git repository (either via
  * setup_git_directory, or in the environment via $GIT_DIR).
diff --git a/refs.c b/refs.c
index 0f3355d2ee..e7070eb743 100644
--- a/refs.c
+++ b/refs.c
@@ -126,7 +126,8 @@ struct ref_namespace_info ref_namespace[] = {
 		 * points to the content of another. Unlike the other
 		 * ref namespaces, this one can be changed by the
 		 * GIT_REPLACE_REF_BASE environment variable. This
-		 * .namespace value will be overwritten in setup_git_env().
+		 * .namespace value will be overwritten during repository
+		 * setup.
 		 */
 		.ref = "refs/replace/",
 		.decoration = DECORATION_GRAFTED,
diff --git a/setup.c b/setup.c
index d723306dfe..252b443117 100644
--- a/setup.c
+++ b/setup.c
@@ -1074,11 +1074,6 @@ static void setup_git_env_internal(struct repository *repo,
 		fetch_if_missing = 0;
 }
 
-static void setup_git_env(struct repository *repo, const char *git_dir)
-{
-	setup_git_env_internal(repo, git_dir, false);
-}
-
 static void set_git_dir_1(struct repository *repo, const char *path, bool skip_initializing_odb)
 {
 	xsetenv(GIT_DIR_ENVIRONMENT, path, 1);
@@ -2023,7 +2018,7 @@ const char *setup_git_directory_gently(struct repository *repo, int *nongit_ok)
 			const char *gitdir = getenv(GIT_DIR_ENVIRONMENT);
 			if (!gitdir)
 				gitdir = DEFAULT_GIT_DIR_ENVIRONMENT;
-			setup_git_env(repo, gitdir);
+			setup_git_env_internal(repo, gitdir, false);
 		}
 		if (startup_info->have_repository) {
 			repo_set_hash_algo(repo, repo_fmt.hash_algo);

-- 
2.54.0.771.g3ed373ac14.dirty

[PATCH 3/8] setup: deduplicate logic to apply repository format

[Patrick Steinhardt]

After having discovered the repository format we then apply it to the
repository so that it knows to use the proper repository extensions. The
logic to apply the format is duplicated across three callsites, which
makes it rather painfull to add new extensions.

Introduce a new function `apply_repository_format()` that takes a repo
and applies a given format to it and adapt all callsites to use it.
While at it, rename `check_repository_format()` to clarify that it
doesn't only _check_ the format, but that it also applies it.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 repository.c | 31 +++++++-------------
 setup.c      | 93 ++++++++++++++++++++++++++++++++----------------------------
 setup.h      |  9 ++++++
 3 files changed, 70 insertions(+), 63 deletions(-)

diff --git a/repository.c b/repository.c
index db57b8308b..58a13f7c4f 100644
--- a/repository.c
+++ b/repository.c
@@ -262,8 +262,8 @@ void repo_set_worktree(struct repository *repo, const char *path)
 	trace2_def_repo(repo);
 }
 
-static int read_and_verify_repository_format(struct repository_format *format,
-					     const char *commondir)
+static int read_repository_format_from_commondir(struct repository_format *format,
+						 const char *commondir)
 {
 	int ret = 0;
 	struct strbuf sb = STRBUF_INIT;
@@ -272,11 +272,6 @@ static int read_and_verify_repository_format(struct repository_format *format,
 	read_repository_format(format, sb.buf);
 	strbuf_reset(&sb);
 
-	if (verify_repository_format(format, &sb) < 0) {
-		warning("%s", sb.buf);
-		ret = -1;
-	}
-
 	strbuf_release(&sb);
 	return ret;
 }
@@ -290,6 +285,8 @@ int repo_init(struct repository *repo,
 	      const char *worktree)
 {
 	struct repository_format format = REPOSITORY_FORMAT_INIT;
+	struct strbuf err = STRBUF_INIT;
+
 	memset(repo, 0, sizeof(*repo));
 
 	initialize_repository(repo);
@@ -297,21 +294,13 @@ int repo_init(struct repository *repo,
 	if (repo_init_gitdir(repo, gitdir))
 		goto error;
 
-	if (read_and_verify_repository_format(&format, repo->commondir))
+	if (read_repository_format_from_commondir(&format, repo->commondir))
 		goto error;
 
-	repo_set_hash_algo(repo, format.hash_algo);
-	repo_set_compat_hash_algo(repo, format.compat_hash_algo);
-	repo_set_ref_storage_format(repo, format.ref_storage_format,
-				    format.ref_storage_payload);
-	repo->repository_format_worktree_config = format.worktree_config;
-	repo->repository_format_relative_worktrees = format.relative_worktrees;
-	repo->repository_format_precious_objects = format.precious_objects;
-	repo->repository_format_submodule_path_cfg = format.submodule_path_cfg;
-
-	/* take ownership of format.partial_clone */
-	repo->repository_format_partial_clone = format.partial_clone;
-	format.partial_clone = NULL;
+	if (apply_repository_format(repo, &format, &err) < 0) {
+		warning("%s", err.buf);
+		goto error;
+	}
 
 	if (worktree)
 		repo_set_worktree(repo, worktree);
@@ -320,10 +309,12 @@ int repo_init(struct repository *repo,
 		repo_read_loose_object_map(repo);
 
 	clear_repository_format(&format);
+	strbuf_release(&err);
 	return 0;
 
 error:
 	clear_repository_format(&format);
+	strbuf_release(&err);
 	repo_clear(repo);
 	return -1;
 }
diff --git a/setup.c b/setup.c
index 252b443117..c5015923f1 100644
--- a/setup.c
+++ b/setup.c
@@ -750,8 +750,7 @@ static int check_repo_format(const char *var, const char *value,
 	return read_worktree_config(var, value, ctx, vdata);
 }
 
-static int check_repository_format_gently(struct repository *repo,
-					  const char *gitdir,
+static int check_repository_format_gently(const char *gitdir,
 					  struct repository_format *candidate,
 					  int *nongit_ok)
 {
@@ -765,7 +764,7 @@ static int check_repository_format_gently(struct repository *repo,
 	strbuf_release(&sb);
 
 	/*
-	 * For historical use of check_repository_format() in git-init,
+	 * For historical use of check_and_apply_repository_format() in git-init,
 	 * we treat a missing config as a silent "ok", even when nongit_ok
 	 * is unset.
 	 */
@@ -782,8 +781,6 @@ static int check_repository_format_gently(struct repository *repo,
 		die("%s", err.buf);
 	}
 
-	repo->repository_format_precious_objects = candidate->precious_objects;
-
 	string_list_clear(&candidate->unknown_extensions, 0);
 	string_list_clear(&candidate->v1_only_extensions, 0);
 
@@ -1140,7 +1137,7 @@ static const char *setup_explicit_git_dir(struct repository *repo,
 		die(_("not a git repository: '%s'"), gitdirenv);
 	}
 
-	if (check_repository_format_gently(repo, gitdirenv, repo_fmt, nongit_ok)) {
+	if (check_repository_format_gently(gitdirenv, repo_fmt, nongit_ok)) {
 		free(gitfile);
 		return NULL;
 	}
@@ -1217,7 +1214,7 @@ static const char *setup_discovered_git_dir(struct repository *repo,
 					    struct repository_format *repo_fmt,
 					    int *nongit_ok)
 {
-	if (check_repository_format_gently(repo, gitdir, repo_fmt, nongit_ok))
+	if (check_repository_format_gently(gitdir, repo_fmt, nongit_ok))
 		return NULL;
 
 	/* --work-tree is set without --git-dir; use discovered one */
@@ -1265,7 +1262,7 @@ static const char *setup_bare_git_dir(struct repository *repo,
 {
 	int root_len;
 
-	if (check_repository_format_gently(repo, ".", repo_fmt, nongit_ok))
+	if (check_repository_format_gently(".", repo_fmt, nongit_ok))
 		return NULL;
 
 	setenv(GIT_IMPLICIT_WORK_TREE_ENVIRONMENT, "0", 1);
@@ -1757,6 +1754,32 @@ enum discovery_result discover_git_directory_reason(struct strbuf *commondir,
 	return result;
 }
 
+int apply_repository_format(struct repository *repo,
+			    const struct repository_format *format,
+			    struct strbuf *err)
+{
+	if (verify_repository_format(format, err) < 0)
+		return -1;
+
+	repo_set_hash_algo(repo, format->hash_algo);
+	repo_set_compat_hash_algo(repo, format->compat_hash_algo);
+	repo_set_ref_storage_format(repo,
+				    format->ref_storage_format,
+				    format->ref_storage_payload);
+	repo->repository_format_worktree_config =
+		format->worktree_config;
+	repo->repository_format_submodule_path_cfg =
+		format->submodule_path_cfg;
+	repo->repository_format_relative_worktrees =
+		format->relative_worktrees;
+	repo->repository_format_partial_clone =
+		xstrdup_or_null(format->partial_clone);
+	repo->repository_format_precious_objects =
+		format->precious_objects;
+
+	return 0;
+}
+
 /*
  * Check the repository format version in the path found in repo_get_git_dir(repo),
  * and die if it is a version we don't understand. Generally one would
@@ -1765,26 +1788,20 @@ enum discovery_result discover_git_directory_reason(struct strbuf *commondir,
  *
  * If successful and fmt is not NULL, fill fmt with data.
  */
-static void check_repository_format(struct repository *repo, struct repository_format *fmt)
+static void check_and_apply_repository_format(struct repository *repo,
+					      struct repository_format *fmt)
 {
 	struct repository_format repo_fmt = REPOSITORY_FORMAT_INIT;
+	struct strbuf err = STRBUF_INIT;
+
 	if (!fmt)
 		fmt = &repo_fmt;
-	check_repository_format_gently(repo, repo_get_git_dir(repo), fmt, NULL);
+
+	check_repository_format_gently(repo_get_git_dir(repo), fmt, NULL);
+	if (apply_repository_format(repo, fmt, &err) < 0)
+		die("%s", err.buf);
 	startup_info->have_repository = 1;
-	repo_set_hash_algo(repo, fmt->hash_algo);
-	repo_set_compat_hash_algo(repo, fmt->compat_hash_algo);
-	repo_set_ref_storage_format(repo,
-				    fmt->ref_storage_format,
-				    fmt->ref_storage_payload);
-	repo->repository_format_worktree_config =
-		fmt->worktree_config;
-	repo->repository_format_submodule_path_cfg =
-		fmt->submodule_path_cfg;
-	repo->repository_format_relative_worktrees =
-		fmt->relative_worktrees;
-	repo->repository_format_partial_clone =
-		xstrdup_or_null(fmt->partial_clone);
+
 	clear_repository_format(&repo_fmt);
 }
 
@@ -1862,7 +1879,7 @@ const char *enter_repo(struct repository *repo, const char *path, unsigned flags
 
 	if (is_git_directory(".")) {
 		set_git_dir(repo, ".", 0);
-		check_repository_format(repo, NULL);
+		check_and_apply_repository_format(repo, NULL);
 		return path;
 	}
 
@@ -2020,25 +2037,15 @@ const char *setup_git_directory_gently(struct repository *repo, int *nongit_ok)
 				gitdir = DEFAULT_GIT_DIR_ENVIRONMENT;
 			setup_git_env_internal(repo, gitdir, false);
 		}
+
 		if (startup_info->have_repository) {
-			repo_set_hash_algo(repo, repo_fmt.hash_algo);
-			repo_set_compat_hash_algo(repo,
-						  repo_fmt.compat_hash_algo);
-			repo_set_ref_storage_format(repo,
-						    repo_fmt.ref_storage_format,
-						    repo_fmt.ref_storage_payload);
-			repo->repository_format_worktree_config =
-				repo_fmt.worktree_config;
-			repo->repository_format_relative_worktrees =
-				repo_fmt.relative_worktrees;
-			repo->repository_format_submodule_path_cfg =
-				repo_fmt.submodule_path_cfg;
-			/* take ownership of repo_fmt.partial_clone */
-			repo->repository_format_partial_clone =
-				repo_fmt.partial_clone;
-			repo_fmt.partial_clone = NULL;
-			repo->repository_format_precious_objects =
-				repo_fmt.precious_objects;
+			struct strbuf err = STRBUF_INIT;
+
+			if (apply_repository_format(repo, &repo_fmt, &err) < 0)
+				die("%s", err.buf);
+
+			clear_repository_format(&repo_fmt);
+			strbuf_release(&err);
 		}
 	}
 	/*
@@ -2814,7 +2821,7 @@ int init_db(struct repository *repo,
 	 * config file, so this will not fail.  What we are catching
 	 * is an attempt to reinitialize new repository with an old tool.
 	 */
-	check_repository_format(repo, &repo_fmt);
+	check_and_apply_repository_format(repo, &repo_fmt);
 
 	repository_format_configure(repo, &repo_fmt, hash, ref_storage_format);
 
diff --git a/setup.h b/setup.h
index 9409326fe4..5ed92f53fa 100644
--- a/setup.h
+++ b/setup.h
@@ -221,6 +221,15 @@ void clear_repository_format(struct repository_format *format);
 int verify_repository_format(const struct repository_format *format,
 			     struct strbuf *err);
 
+/*
+ * Apply the given repository format to the repo. This initializes extensions
+ * and basic data structures required for normal operation. Returns 0 on
+ * success, a negative error code otherwise.
+ */
+int apply_repository_format(struct repository *repo,
+			    const struct repository_format *format,
+			    struct strbuf *err);
+
 const char *get_template_dir(const char *option_template);
 
 #define INIT_DB_QUIET      (1 << 0)

-- 
2.54.0.771.g3ed373ac14.dirty

[PATCH 4/8] repository: stop initializing the object database in `repo_set_gitdir()`

[Patrick Steinhardt]

The function `repo_set_gitdir()` obviously sets the Git directory for a
given repository. Less obviously though, the function also configures a
couple of auxiliary settings.

One such thing is that we create the object database in this function.
This logic only happens conditionally though, as `set_git_dir()` may be
called multiple times during repository setup, and we don't want to
create the object database multiple times. This is somewhat tangled and
hard to follow.

Remove the logic from `repo_set_gitdir()` and instead initialize the
object database outside of it. This leads to some duplication right now,
but that duplication will be removed in a subsequent step where we will
start initializing the object database as part of applying the repo's
format.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 repository.c | 8 ++------
 repository.h | 3 ---
 setup.c      | 7 ++++---
 3 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/repository.c b/repository.c
index 58a13f7c4f..2c2395105f 100644
--- a/repository.c
+++ b/repository.c
@@ -181,12 +181,6 @@ void repo_set_gitdir(struct repository *repo,
 	free(old_gitdir);
 
 	repo_set_commondir(repo, o->commondir);
-
-	if (!repo->objects)
-		repo->objects = odb_new(repo, o->object_dir, o->alternate_db);
-	else if (!o->skip_initializing_odb)
-		BUG("cannot reinitialize an already-initialized object directory");
-
 	repo->disable_ref_updates = o->disable_ref_updates;
 
 	expand_base_dir(&repo->graft_file, o->graft_file,
@@ -302,6 +296,8 @@ int repo_init(struct repository *repo,
 		goto error;
 	}
 
+	repo->objects = odb_new(repo, NULL, NULL);
+
 	if (worktree)
 		repo_set_worktree(repo, worktree);
 
diff --git a/repository.h b/repository.h
index c3ec0f4b79..36e2db2633 100644
--- a/repository.h
+++ b/repository.h
@@ -221,12 +221,9 @@ const char *repo_get_work_tree(struct repository *repo);
  */
 struct set_gitdir_args {
 	const char *commondir;
-	const char *object_dir;
 	const char *graft_file;
 	const char *index_file;
-	const char *alternate_db;
 	bool disable_ref_updates;
-	bool skip_initializing_odb;
 };
 
 void repo_set_gitdir(struct repository *repo, const char *root,
diff --git a/setup.c b/setup.c
index c5015923f1..3bd3f6c592 100644
--- a/setup.c
+++ b/setup.c
@@ -1045,17 +1045,18 @@ static void setup_git_env_internal(struct repository *repo,
 	struct strvec to_free = STRVEC_INIT;
 
 	args.commondir = getenv_safe(&to_free, GIT_COMMON_DIR_ENVIRONMENT);
-	args.object_dir = getenv_safe(&to_free, DB_ENVIRONMENT);
 	args.graft_file = getenv_safe(&to_free, GRAFT_ENVIRONMENT);
 	args.index_file = getenv_safe(&to_free, INDEX_ENVIRONMENT);
-	args.alternate_db = getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT);
 	if (getenv(GIT_QUARANTINE_ENVIRONMENT))
 		args.disable_ref_updates = true;
-	args.skip_initializing_odb = skip_initializing_odb;
 
 	repo_set_gitdir(repo, git_dir, &args);
 	strvec_clear(&to_free);
 
+	if (!skip_initializing_odb)
+		repo->objects = odb_new(repo, getenv_safe(&to_free, DB_ENVIRONMENT),
+					getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
+
 	if (getenv(NO_REPLACE_OBJECTS_ENVIRONMENT))
 		disable_replace_refs();
 	replace_ref_base = getenv(GIT_REPLACE_REF_BASE_ENVIRONMENT);

-- 
2.54.0.771.g3ed373ac14.dirty

[PATCH 5/8] setup: stop creating the object database in `setup_git_env()`

[Patrick Steinhardt]

In the preceding commit we have stopped creating the object database in
`repo_set_gitdir()`. But the logic is still somewhat confusing as we
still end up creating it conditionally in `setup_git_dir()`, which is
called multiple times.

Drop the conditional logic and instead create the object database in all
places where we have discovered and configured a repository.

This leads to even more duplication than we already had in the preceding
commit, but an alert reader may notice that we now (almost) always call
`odb_new()` directly before having called `apply_repository_format()`.
The only exception to this is `setup_git_directory_gently()`, where we
also call the function when _not_ applying the repository format. This
will be fixed in the next commit, and once that's done we can then unify
creation of the object database into `apply_repository_format()`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 setup.c | 37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/setup.c b/setup.c
index 3bd3f6c592..0dc9fe4565 100644
--- a/setup.c
+++ b/setup.c
@@ -1035,8 +1035,7 @@ const char *read_gitfile_gently(const char *path, int *return_error_code)
 }
 
 static void setup_git_env_internal(struct repository *repo,
-				   const char *git_dir,
-				   bool skip_initializing_odb)
+				   const char *git_dir)
 {
 	char *git_replace_ref_base;
 	const char *shallow_file;
@@ -1053,10 +1052,6 @@ static void setup_git_env_internal(struct repository *repo,
 	repo_set_gitdir(repo, git_dir, &args);
 	strvec_clear(&to_free);
 
-	if (!skip_initializing_odb)
-		repo->objects = odb_new(repo, getenv_safe(&to_free, DB_ENVIRONMENT),
-					getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
-
 	if (getenv(NO_REPLACE_OBJECTS_ENVIRONMENT))
 		disable_replace_refs();
 	replace_ref_base = getenv(GIT_REPLACE_REF_BASE_ENVIRONMENT);
@@ -1072,10 +1067,10 @@ static void setup_git_env_internal(struct repository *repo,
 		fetch_if_missing = 0;
 }
 
-static void set_git_dir_1(struct repository *repo, const char *path, bool skip_initializing_odb)
+static void set_git_dir_1(struct repository *repo, const char *path)
 {
 	xsetenv(GIT_DIR_ENVIRONMENT, path, 1);
-	setup_git_env_internal(repo, path, skip_initializing_odb);
+	setup_git_env_internal(repo, path);
 }
 
 static void update_relative_gitdir(const char *name UNUSED,
@@ -1089,7 +1084,7 @@ static void update_relative_gitdir(const char *name UNUSED,
 	trace_printf_key(&trace_setup_key,
 			 "setup: move $GIT_DIR to '%s'",
 			 path);
-	set_git_dir_1(repo, path, true);
+	set_git_dir_1(repo, path);
 	free(path);
 }
 
@@ -1102,7 +1097,7 @@ static void set_git_dir(struct repository *repo, const char *path, int make_real
 		path = realpath.buf;
 	}
 
-	set_git_dir_1(repo, path, false);
+	set_git_dir_1(repo, path);
 	if (!is_absolute_path(path))
 		chdir_notify_register(NULL, update_relative_gitdir, repo);
 
@@ -1879,8 +1874,15 @@ const char *enter_repo(struct repository *repo, const char *path, unsigned flags
 	}
 
 	if (is_git_directory(".")) {
+		struct strvec to_free = STRVEC_INIT;
+
 		set_git_dir(repo, ".", 0);
+		repo->objects = odb_new(repo,
+					getenv_safe(&to_free, DB_ENVIRONMENT),
+					getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
 		check_and_apply_repository_format(repo, NULL);
+
+		strvec_clear(&to_free);
 		return path;
 	}
 
@@ -2032,13 +2034,19 @@ const char *setup_git_directory_gently(struct repository *repo, int *nongit_ok)
 	    startup_info->have_repository ||
 	    /* GIT_DIR_EXPLICIT */
 	    getenv(GIT_DIR_ENVIRONMENT)) {
+		struct strvec to_free = STRVEC_INIT;
+
 		if (!repo->gitdir) {
 			const char *gitdir = getenv(GIT_DIR_ENVIRONMENT);
 			if (!gitdir)
 				gitdir = DEFAULT_GIT_DIR_ENVIRONMENT;
-			setup_git_env_internal(repo, gitdir, false);
+			setup_git_env_internal(repo, gitdir);
 		}
 
+		repo->objects = odb_new(repo,
+					getenv_safe(&to_free, DB_ENVIRONMENT),
+					getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
+
 		if (startup_info->have_repository) {
 			struct strbuf err = STRBUF_INIT;
 
@@ -2048,6 +2056,8 @@ const char *setup_git_directory_gently(struct repository *repo, int *nongit_ok)
 			clear_repository_format(&repo_fmt);
 			strbuf_release(&err);
 		}
+
+		strvec_clear(&to_free);
 	}
 	/*
 	 * Since precompose_string_if_needed() needs to look at
@@ -2796,6 +2806,7 @@ int init_db(struct repository *repo,
 	int exist_ok = flags & INIT_DB_EXIST_OK;
 	char *original_git_dir = real_pathdup(git_dir, 1);
 	struct repository_format repo_fmt = REPOSITORY_FORMAT_INIT;
+	struct strvec to_free = STRVEC_INIT;
 
 	if (real_git_dir) {
 		struct stat st;
@@ -2816,6 +2827,9 @@ int init_db(struct repository *repo,
 	}
 	startup_info->have_repository = 1;
 
+	repo->objects = odb_new(repo, getenv_safe(&to_free, DB_ENVIRONMENT),
+				getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
+
 	/*
 	 * Check to see if the repository version is right.
 	 * Note that a newly created repository does not have
@@ -2879,6 +2893,7 @@ int init_db(struct repository *repo,
 	}
 
 	clear_repository_format(&repo_fmt);
+	strvec_clear(&to_free);
 	free(original_git_dir);
 	return 0;
 }

-- 
2.54.0.771.g3ed373ac14.dirty

[PATCH 6/8] setup: stop initializing object database without repository

[Patrick Steinhardt]

The function `setup_git_directory_gently()` is responsible for
discovering and setting up a Git repository based on various environment
variables and the current working directory. The result is thus a fully
usable Git repository.

One oddity of this function is that we may set up the object database
even in the case where we don't have a repository, namely in the case
where the `GIT_DIR_EXPLICIT` environment variable is set but points to a
non-existent repository. If so, we call `setup_git_env_internal()` with
the value of the environment variable so that the repository's Git
directory is configured, even if it points to a non-existent directory.

Historically though, this function didn't only configure the repository,
but also initialized the object database. We retained this behaviour
from a preceding commit, even though it really doesn't make much sense
in the first place -- there is no repository, so we don't have an object
database either. There seemingly isn't much of a reason to construct the
object database, as we typically won't try to read objects when we don't
have an object database.

There's one exception though: git-index-pack(1) may run outside of a
repository, which can be used to perform consistency checks for a
packfile. The code path is _almost_ working: we already know to call
`parse_object_buffer()`, which can read objects without an object
database being available. And that works for all object types except for
commits, because `parse_commit_buffer()` calls `parse_commit_graph()`,
and that function doesn't handle the case where we don't have an object
database.

Fix this instance to check for the object database instead of checking
for the Git directory having been initialized. With this fixed, we can
now stop constructing an object database completely.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 commit-graph.c | 4 ++--
 setup.c        | 7 +++----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index 9abe62bd5a..0820cf5fb8 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -740,13 +740,13 @@ static struct commit_graph *prepare_commit_graph(struct repository *r)
 	struct odb_source *source;
 
 	/*
-	 * Early return if there is no git dir or if the commit graph is
+	 * Early return if there is no object database or if the commit graph is
 	 * disabled.
 	 *
 	 * This must come before the "already attempted?" check below, because
 	 * we want to disable even an already-loaded graph file.
 	 */
-	if (!r->gitdir || r->commit_graph_disabled)
+	if (!r->objects || r->commit_graph_disabled)
 		return NULL;
 
 	if (r->objects->commit_graph_attempted)
diff --git a/setup.c b/setup.c
index 0dc9fe4565..4a8d6230b1 100644
--- a/setup.c
+++ b/setup.c
@@ -2043,13 +2043,12 @@ const char *setup_git_directory_gently(struct repository *repo, int *nongit_ok)
 			setup_git_env_internal(repo, gitdir);
 		}
 
-		repo->objects = odb_new(repo,
-					getenv_safe(&to_free, DB_ENVIRONMENT),
-					getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
-
 		if (startup_info->have_repository) {
 			struct strbuf err = STRBUF_INIT;
 
+			repo->objects = odb_new(repo,
+						getenv_safe(&to_free, DB_ENVIRONMENT),
+						getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
 			if (apply_repository_format(repo, &repo_fmt, &err) < 0)
 				die("%s", err.buf);
 

-- 
2.54.0.771.g3ed373ac14.dirty

[PATCH 7/8] repository: stop reading loose object map twice on repo init

[Patrick Steinhardt]

When initializing a repository via `repo_init()` we end up reading the
loose object map twice:

  - `apply_repository_format()` calls `repo_set_compat_hash_algo()`,
    which in turn calls `repo_read_loose_object_map()` if we have a
    compatibility hash configured.

  - `repo_init()` calls `repo_read_loose_object_map()` directly a second
    time.

Drop the second read of the loose object map in `repo_init()`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 repository.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/repository.c b/repository.c
index 2c2395105f..61dfbb8be6 100644
--- a/repository.c
+++ b/repository.c
@@ -301,9 +301,6 @@ int repo_init(struct repository *repo,
 	if (worktree)
 		repo_set_worktree(repo, worktree);
 
-	if (repo->compat_hash_algo)
-		repo_read_loose_object_map(repo);
-
 	clear_repository_format(&format);
 	strbuf_release(&err);
 	return 0;

-- 
2.54.0.771.g3ed373ac14.dirty

[PATCH 8/8] setup: construct object database in `apply_repository_format()`

[Patrick Steinhardt]

With the preceding changes we now always construct the repository's
object database before applying the repository format. Remove this
duplication by constructing it in `apply_repository_format()` instead.

Note that we create the object database _after_ having set up the
repository's hash algorithm, but _before_ setting the compat hash
algorithm. This is intentional:

  - Constructing the object database may require knowledge of its
    intended object format.

  - Setting up the compatibility hash requires the object database to be
    initialized already, because we immediately read the loose object
    map.

The first point is sensible, the second maybe a little less so. Ideally,
it should be the responsibility of the object database itself to
initialize any data structures required for the compatibility hash. But
this would require further changes, so this is kept as-is for now.

Further note that this requires us to move handling of the environment
variables GIT_OBJECT_DIRECTORY and GIT_ALTERNATE_OBJECT_DIRECTORIES into
the repository format, as well. This allows the caller more flexibility
around whether or not those environment variables are being honored, as
we do do want to respect them in "setup.c", but not in "repository.c".

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 repository.c |  4 +---
 setup.c      | 45 +++++++++++++++++++++------------------------
 setup.h      | 10 ++++++++++
 3 files changed, 32 insertions(+), 27 deletions(-)

diff --git a/repository.c b/repository.c
index 61dfbb8be6..187dd471c4 100644
--- a/repository.c
+++ b/repository.c
@@ -291,13 +291,11 @@ int repo_init(struct repository *repo,
 	if (read_repository_format_from_commondir(&format, repo->commondir))
 		goto error;
 
-	if (apply_repository_format(repo, &format, &err) < 0) {
+	if (apply_repository_format(repo, &format, 0, &err) < 0) {
 		warning("%s", err.buf);
 		goto error;
 	}
 
-	repo->objects = odb_new(repo, NULL, NULL);
-
 	if (worktree)
 		repo_set_worktree(repo, worktree);
 
diff --git a/setup.c b/setup.c
index 4a8d6230b1..513fc88749 100644
--- a/setup.c
+++ b/setup.c
@@ -1752,12 +1752,22 @@ enum discovery_result discover_git_directory_reason(struct strbuf *commondir,
 
 int apply_repository_format(struct repository *repo,
 			    const struct repository_format *format,
+			    enum apply_repository_format_flags flags,
 			    struct strbuf *err)
 {
+	char *object_directory = NULL, *alternate_object_directories = NULL;
+
 	if (verify_repository_format(format, err) < 0)
 		return -1;
 
+	if (flags & APPLY_REPOSITORY_FORMAT_HONOR_ENV) {
+		object_directory = xstrdup_or_null(getenv(DB_ENVIRONMENT));
+		alternate_object_directories = xstrdup_or_null(getenv(ALTERNATE_DB_ENVIRONMENT));
+	}
+
 	repo_set_hash_algo(repo, format->hash_algo);
+	repo->objects = odb_new(repo, object_directory,
+				alternate_object_directories);
 	repo_set_compat_hash_algo(repo, format->compat_hash_algo);
 	repo_set_ref_storage_format(repo,
 				    format->ref_storage_format,
@@ -1773,6 +1783,8 @@ int apply_repository_format(struct repository *repo,
 	repo->repository_format_precious_objects =
 		format->precious_objects;
 
+	free(alternate_object_directories);
+	free(object_directory);
 	return 0;
 }
 
@@ -1785,7 +1797,8 @@ int apply_repository_format(struct repository *repo,
  * If successful and fmt is not NULL, fill fmt with data.
  */
 static void check_and_apply_repository_format(struct repository *repo,
-					      struct repository_format *fmt)
+					      struct repository_format *fmt,
+					      enum apply_repository_format_flags flags)
 {
 	struct repository_format repo_fmt = REPOSITORY_FORMAT_INIT;
 	struct strbuf err = STRBUF_INIT;
@@ -1794,7 +1807,7 @@ static void check_and_apply_repository_format(struct repository *repo,
 		fmt = &repo_fmt;
 
 	check_repository_format_gently(repo_get_git_dir(repo), fmt, NULL);
-	if (apply_repository_format(repo, fmt, &err) < 0)
+	if (apply_repository_format(repo, fmt, flags, &err) < 0)
 		die("%s", err.buf);
 	startup_info->have_repository = 1;
 
@@ -1874,15 +1887,9 @@ const char *enter_repo(struct repository *repo, const char *path, unsigned flags
 	}
 
 	if (is_git_directory(".")) {
-		struct strvec to_free = STRVEC_INIT;
-
 		set_git_dir(repo, ".", 0);
-		repo->objects = odb_new(repo,
-					getenv_safe(&to_free, DB_ENVIRONMENT),
-					getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
-		check_and_apply_repository_format(repo, NULL);
-
-		strvec_clear(&to_free);
+		check_and_apply_repository_format(repo, NULL,
+						  APPLY_REPOSITORY_FORMAT_HONOR_ENV);
 		return path;
 	}
 
@@ -2034,8 +2041,6 @@ const char *setup_git_directory_gently(struct repository *repo, int *nongit_ok)
 	    startup_info->have_repository ||
 	    /* GIT_DIR_EXPLICIT */
 	    getenv(GIT_DIR_ENVIRONMENT)) {
-		struct strvec to_free = STRVEC_INIT;
-
 		if (!repo->gitdir) {
 			const char *gitdir = getenv(GIT_DIR_ENVIRONMENT);
 			if (!gitdir)
@@ -2046,17 +2051,13 @@ const char *setup_git_directory_gently(struct repository *repo, int *nongit_ok)
 		if (startup_info->have_repository) {
 			struct strbuf err = STRBUF_INIT;
 
-			repo->objects = odb_new(repo,
-						getenv_safe(&to_free, DB_ENVIRONMENT),
-						getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
-			if (apply_repository_format(repo, &repo_fmt, &err) < 0)
+			if (apply_repository_format(repo, &repo_fmt,
+						    APPLY_REPOSITORY_FORMAT_HONOR_ENV, &err) < 0)
 				die("%s", err.buf);
 
 			clear_repository_format(&repo_fmt);
 			strbuf_release(&err);
 		}
-
-		strvec_clear(&to_free);
 	}
 	/*
 	 * Since precompose_string_if_needed() needs to look at
@@ -2805,7 +2806,6 @@ int init_db(struct repository *repo,
 	int exist_ok = flags & INIT_DB_EXIST_OK;
 	char *original_git_dir = real_pathdup(git_dir, 1);
 	struct repository_format repo_fmt = REPOSITORY_FORMAT_INIT;
-	struct strvec to_free = STRVEC_INIT;
 
 	if (real_git_dir) {
 		struct stat st;
@@ -2826,16 +2826,14 @@ int init_db(struct repository *repo,
 	}
 	startup_info->have_repository = 1;
 
-	repo->objects = odb_new(repo, getenv_safe(&to_free, DB_ENVIRONMENT),
-				getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
-
 	/*
 	 * Check to see if the repository version is right.
 	 * Note that a newly created repository does not have
 	 * config file, so this will not fail.  What we are catching
 	 * is an attempt to reinitialize new repository with an old tool.
 	 */
-	check_and_apply_repository_format(repo, &repo_fmt);
+	check_and_apply_repository_format(repo, &repo_fmt,
+					  APPLY_REPOSITORY_FORMAT_HONOR_ENV);
 
 	repository_format_configure(repo, &repo_fmt, hash, ref_storage_format);
 
@@ -2892,7 +2890,6 @@ int init_db(struct repository *repo,
 	}
 
 	clear_repository_format(&repo_fmt);
-	strvec_clear(&to_free);
 	free(original_git_dir);
 	return 0;
 }
diff --git a/setup.h b/setup.h
index 5ed92f53fa..821b55aca0 100644
--- a/setup.h
+++ b/setup.h
@@ -221,6 +221,15 @@ void clear_repository_format(struct repository_format *format);
 int verify_repository_format(const struct repository_format *format,
 			     struct strbuf *err);
 
+enum apply_repository_format_flags {
+	/*
+	 * Honor environment variables when applying the repository format to
+	 * the repository. For now, this only covers environment variables that
+	 * relate to the object database.
+	 */
+	APPLY_REPOSITORY_FORMAT_HONOR_ENV = (1 << 0),
+};
+
 /*
  * Apply the given repository format to the repo. This initializes extensions
  * and basic data structures required for normal operation. Returns 0 on
@@ -228,6 +237,7 @@ int verify_repository_format(const struct repository_format *format,
  */
 int apply_repository_format(struct repository *repo,
 			    const struct repository_format *format,
+			    enum apply_repository_format_flags flags,
 			    struct strbuf *err);
 
 const char *get_template_dir(const char *option_template);

-- 
2.54.0.771.g3ed373ac14.dirty

Re: [PATCH 8/8] setup: construct object database in `apply_repository_format()`

[Junio C Hamano]

Patrick Steinhardt <ps@pks.im> writes:

> With the preceding changes we now always construct the repository's
> object database before applying the repository format. Remove this
> duplication by constructing it in `apply_repository_format()` instead.
>
> Note that we create the object database _after_ having set up the
> repository's hash algorithm, but _before_ setting the compat hash
> algorithm. This is intentional:
>
>   - Constructing the object database may require knowledge of its
>     intended object format.
>
>   - Setting up the compatibility hash requires the object database to be
>     initialized already, because we immediately read the loose object
>     map.
>
> The first point is sensible, the second maybe a little less so. Ideally,
> it should be the responsibility of the object database itself to
> initialize any data structures required for the compatibility hash. But
> this would require further changes, so this is kept as-is for now.

Yeah, I guess it is a good place to stop, instead of solving the
chicken-and-egg problem in one go.

> Further note that this requires us to move handling of the environment
> variables GIT_OBJECT_DIRECTORY and GIT_ALTERNATE_OBJECT_DIRECTORIES into
> the repository format, as well. This allows the caller more flexibility
> around whether or not those environment variables are being honored, as
> we do do want to respect them in "setup.c", but not in "repository.c".

It seems that we really really really want to do so ;-).  "do do
want to" -> "do want to" or even "want to", perhaps.

> Signed-off-by: Patrick Steinhardt <ps@pks.im>
> ---
>  repository.c |  4 +---
>  setup.c      | 45 +++++++++++++++++++++------------------------
>  setup.h      | 10 ++++++++++
>  3 files changed, 32 insertions(+), 27 deletions(-)
>
> diff --git a/repository.c b/repository.c
> index 61dfbb8be6..187dd471c4 100644
> --- a/repository.c
> +++ b/repository.c
> @@ -291,13 +291,11 @@ int repo_init(struct repository *repo,
>  	if (read_repository_format_from_commondir(&format, repo->commondir))
>  		goto error;
>  
> -	if (apply_repository_format(repo, &format, &err) < 0) {
> +	if (apply_repository_format(repo, &format, 0, &err) < 0) {
>  		warning("%s", err.buf);
>  		goto error;
>  	}
>  
> -	repo->objects = odb_new(repo, NULL, NULL);
> -
>  	if (worktree)
>  		repo_set_worktree(repo, worktree);
>  
> diff --git a/setup.c b/setup.c
> index 4a8d6230b1..513fc88749 100644
> --- a/setup.c
> +++ b/setup.c
> @@ -1752,12 +1752,22 @@ enum discovery_result discover_git_directory_reason(struct strbuf *commondir,
>  
>  int apply_repository_format(struct repository *repo,
>  			    const struct repository_format *format,
> +			    enum apply_repository_format_flags flags,
>  			    struct strbuf *err)
>  {
> +	char *object_directory = NULL, *alternate_object_directories = NULL;
> +
>  	if (verify_repository_format(format, err) < 0)
>  		return -1;
>  
> +	if (flags & APPLY_REPOSITORY_FORMAT_HONOR_ENV) {
> +		object_directory = xstrdup_or_null(getenv(DB_ENVIRONMENT));
> +		alternate_object_directories = xstrdup_or_null(getenv(ALTERNATE_DB_ENVIRONMENT));
> +	}
> +
>  	repo_set_hash_algo(repo, format->hash_algo);
> +	repo->objects = odb_new(repo, object_directory,
> +				alternate_object_directories);
>  	repo_set_compat_hash_algo(repo, format->compat_hash_algo);
>  	repo_set_ref_storage_format(repo,
>  				    format->ref_storage_format,
> @@ -1773,6 +1783,8 @@ int apply_repository_format(struct repository *repo,
>  	repo->repository_format_precious_objects =
>  		format->precious_objects;
>  
> +	free(alternate_object_directories);
> +	free(object_directory);
>  	return 0;
>  }
>  
> @@ -1785,7 +1797,8 @@ int apply_repository_format(struct repository *repo,
>   * If successful and fmt is not NULL, fill fmt with data.
>   */
>  static void check_and_apply_repository_format(struct repository *repo,
> -					      struct repository_format *fmt)
> +					      struct repository_format *fmt,
> +					      enum apply_repository_format_flags flags)
>  {
>  	struct repository_format repo_fmt = REPOSITORY_FORMAT_INIT;
>  	struct strbuf err = STRBUF_INIT;
> @@ -1794,7 +1807,7 @@ static void check_and_apply_repository_format(struct repository *repo,
>  		fmt = &repo_fmt;
>  
>  	check_repository_format_gently(repo_get_git_dir(repo), fmt, NULL);
> -	if (apply_repository_format(repo, fmt, &err) < 0)
> +	if (apply_repository_format(repo, fmt, flags, &err) < 0)
>  		die("%s", err.buf);
>  	startup_info->have_repository = 1;
>  
> @@ -1874,15 +1887,9 @@ const char *enter_repo(struct repository *repo, const char *path, unsigned flags
>  	}
>  
>  	if (is_git_directory(".")) {
> -		struct strvec to_free = STRVEC_INIT;
> -
>  		set_git_dir(repo, ".", 0);
> -		repo->objects = odb_new(repo,
> -					getenv_safe(&to_free, DB_ENVIRONMENT),
> -					getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
> -		check_and_apply_repository_format(repo, NULL);
> -
> -		strvec_clear(&to_free);
> +		check_and_apply_repository_format(repo, NULL,
> +						  APPLY_REPOSITORY_FORMAT_HONOR_ENV);
>  		return path;
>  	}
>  
> @@ -2034,8 +2041,6 @@ const char *setup_git_directory_gently(struct repository *repo, int *nongit_ok)
>  	    startup_info->have_repository ||
>  	    /* GIT_DIR_EXPLICIT */
>  	    getenv(GIT_DIR_ENVIRONMENT)) {
> -		struct strvec to_free = STRVEC_INIT;
> -
>  		if (!repo->gitdir) {
>  			const char *gitdir = getenv(GIT_DIR_ENVIRONMENT);
>  			if (!gitdir)
> @@ -2046,17 +2051,13 @@ const char *setup_git_directory_gently(struct repository *repo, int *nongit_ok)
>  		if (startup_info->have_repository) {
>  			struct strbuf err = STRBUF_INIT;
>  
> -			repo->objects = odb_new(repo,
> -						getenv_safe(&to_free, DB_ENVIRONMENT),
> -						getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
> -			if (apply_repository_format(repo, &repo_fmt, &err) < 0)
> +			if (apply_repository_format(repo, &repo_fmt,
> +						    APPLY_REPOSITORY_FORMAT_HONOR_ENV, &err) < 0)
>  				die("%s", err.buf);
>  
>  			clear_repository_format(&repo_fmt);
>  			strbuf_release(&err);
>  		}
> -
> -		strvec_clear(&to_free);
>  	}
>  	/*
>  	 * Since precompose_string_if_needed() needs to look at
> @@ -2805,7 +2806,6 @@ int init_db(struct repository *repo,
>  	int exist_ok = flags & INIT_DB_EXIST_OK;
>  	char *original_git_dir = real_pathdup(git_dir, 1);
>  	struct repository_format repo_fmt = REPOSITORY_FORMAT_INIT;
> -	struct strvec to_free = STRVEC_INIT;
>  
>  	if (real_git_dir) {
>  		struct stat st;
> @@ -2826,16 +2826,14 @@ int init_db(struct repository *repo,
>  	}
>  	startup_info->have_repository = 1;
>  
> -	repo->objects = odb_new(repo, getenv_safe(&to_free, DB_ENVIRONMENT),
> -				getenv_safe(&to_free, ALTERNATE_DB_ENVIRONMENT));
> -
>  	/*
>  	 * Check to see if the repository version is right.
>  	 * Note that a newly created repository does not have
>  	 * config file, so this will not fail.  What we are catching
>  	 * is an attempt to reinitialize new repository with an old tool.
>  	 */
> -	check_and_apply_repository_format(repo, &repo_fmt);
> +	check_and_apply_repository_format(repo, &repo_fmt,
> +					  APPLY_REPOSITORY_FORMAT_HONOR_ENV);
>  
>  	repository_format_configure(repo, &repo_fmt, hash, ref_storage_format);
>  
> @@ -2892,7 +2890,6 @@ int init_db(struct repository *repo,
>  	}
>  
>  	clear_repository_format(&repo_fmt);
> -	strvec_clear(&to_free);
>  	free(original_git_dir);
>  	return 0;
>  }
> diff --git a/setup.h b/setup.h
> index 5ed92f53fa..821b55aca0 100644
> --- a/setup.h
> +++ b/setup.h
> @@ -221,6 +221,15 @@ void clear_repository_format(struct repository_format *format);
>  int verify_repository_format(const struct repository_format *format,
>  			     struct strbuf *err);
>  
> +enum apply_repository_format_flags {
> +	/*
> +	 * Honor environment variables when applying the repository format to
> +	 * the repository. For now, this only covers environment variables that
> +	 * relate to the object database.
> +	 */
> +	APPLY_REPOSITORY_FORMAT_HONOR_ENV = (1 << 0),
> +};
> +
>  /*
>   * Apply the given repository format to the repo. This initializes extensions
>   * and basic data structures required for normal operation. Returns 0 on
> @@ -228,6 +237,7 @@ int verify_repository_format(const struct repository_format *format,
>   */
>  int apply_repository_format(struct repository *repo,
>  			    const struct repository_format *format,
> +			    enum apply_repository_format_flags flags,
>  			    struct strbuf *err);
>  
>  const char *get_template_dir(const char *option_template);