Re: [PATCH 3/5] setup: defer object database creation

In a subsequent commit we'll make the creation of the on-disk data
structures of an object database pluggable. This will lead to an
in-between state where we have already configured the repository's
object database, but it's not usable yet until we eventually call
`create_object_directory()`.

Defer the object database creation so that we handle both steps in the
same function.

Signed-off-by: Patrick Steinhardt <redacted>
---
 setup.c | 35 +++++++++++++++++++++++++++--------
 setup.h |  9 +++++++++
 2 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/setup.c b/setup.c
index 825572f5f1..a7b1b9eaef 100644
--- a/setup.c
+++ b/setup.c

@@ -1760,6 +1760,13 @@ enum discovery_result discover_git_directory_reason(struct strbuf *commondir,
 	return result;
 }
 
+static void get_object_directories(char **object_directory,
+				   char **alternate_object_directories)
+{
+	*object_directory = xstrdup_or_null(getenv(DB_ENVIRONMENT));
+	*alternate_object_directories = xstrdup_or_null(getenv(ALTERNATE_DB_ENVIRONMENT));
+}
+
 int apply_repository_format(struct repository *repo,
 			    const struct repository_format *format,
 			    enum apply_repository_format_flags flags,

@@ -1779,8 +1786,9 @@ int apply_repository_format(struct repository *repo,
 	if (flags & APPLY_REPOSITORY_FORMAT_HONOR_ENV) {
 		const char *shallow_file;
 
-		object_directory = xstrdup_or_null(getenv(DB_ENVIRONMENT));
-		alternate_object_directories = xstrdup_or_null(getenv(ALTERNATE_DB_ENVIRONMENT));
+		get_object_directories(&object_directory,
+				       &alternate_object_directories);
+
 		shallow_file = getenv(GIT_SHALLOW_FILE_ENVIRONMENT);
 		if (shallow_file)
 			set_alternate_shallow_file(repo, shallow_file);

@@ -1803,8 +1811,9 @@ int apply_repository_format(struct repository *repo,
 	repo->repository_format_precious_objects =
 		format->precious_objects;
 
-	repo->objects = odb_new(repo, object_directory,
-				alternate_object_directories);
+	if (!(flags & APPLY_REPOSITORY_FORMAT_SKIP_ODB_CREATION))
+		repo->objects = odb_new(repo, object_directory,
+					alternate_object_directories);

-static void create_object_directory(struct repository *repo)
+static void create_object_database(struct repository *repo)
 {
+	char *object_directory, *alternate_object_directories;
 	struct strbuf path = STRBUF_INIT;
 	size_t baselen;
 
+	get_object_directories(&object_directory, &alternate_object_directories);
+	repo->objects = odb_new(repo, object_directory,
+				alternate_object_directories);
+
 	strbuf_addstr(&path, repo_get_object_directory(repo));
 	baselen = path.len;
 

@@ -2672,6 +2686,8 @@ static void create_object_directory(struct repository *repo)
 	strbuf_addstr(&path, "/info");
 	safe_create_dir(repo, path.buf, 1);
 
+	free(alternate_object_directories);
+	free(object_directory);
 	strbuf_release(&path);
 }
 

@@ -2867,9 +2883,10 @@ int init_db(struct repository *repo,
 	 */
 	read_and_verify_repository_format(&repo_fmt, repo_get_git_dir(repo), NULL);
 	repository_format_configure(&repo_fmt, hash, ref_storage_format);
-	if (apply_repository_format(repo, &repo_fmt, APPLY_REPOSITORY_FORMAT_HONOR_ENV, &err) < 0)
+	if (apply_repository_format(repo, &repo_fmt,
+				    APPLY_REPOSITORY_FORMAT_HONOR_ENV |
+				    APPLY_REPOSITORY_FORMAT_SKIP_ODB_CREATION, &err) < 0)
 		die("%s", err.buf);
-	startup_info->have_repository = 1;

@@ -2885,7 +2902,9 @@ int init_db(struct repository *repo,
 
 	if (!(flags & INIT_DB_SKIP_REFDB))
 		create_reference_database(repo, initial_branch, flags & INIT_DB_QUIET);
-	create_object_directory(repo);
+	create_object_database(repo);
+
+	startup_info->have_repository = 1;

diff --git a/setup.h b/setup.h
index 654f10e059..e55d647b70 100644
--- a/setup.h
+++ b/setup.h

@@ -241,6 +241,15 @@ enum apply_repository_format_flags {
 	 * relate to the object database.
 	 */
 	APPLY_REPOSITORY_FORMAT_HONOR_ENV = (1 << 0),
+
+	/*
+	 * Usually, the object database is created after the repository format
+	 * was applied. This step is skipped if this flag is set, which leaves
+	 * us with a partially-working repository.
+	 *
+	 * This is useful when initializing a new repository.
+	 */
+	APPLY_REPOSITORY_FORMAT_SKIP_ODB_CREATION = (1 << 1),
 };