setup: construct object database in apply_repository_format()

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 want to respect them in "setup.c", but not in "repository.c".

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

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);
 

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;
 }

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);