sha1_file.c: move delayed getenv(altdb) back to setup_git_env()

getenv() is supposed to work on the main repository only. This delayed
getenv() code in sha1_file.c makes it more difficult to convert
sha1_file.c to a generic object store that could be used by both
submodule and main repositories.

Move the getenv() back in setup_git_env() where other env vars are
also fetched.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

environment.c

@@ -174,6 +174,7 @@ void setup_git_env(const char *git_dir)
 	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);
 	repo_set_gitdir(the_repository, git_dir, &args);
 	argv_array_clear(&to_free);
 

repository.c

@@ -60,6 +60,8 @@ void repo_set_gitdir(struct repository *repo,
 	repo_set_commondir(repo, o->commondir);
 	expand_base_dir(&repo->objectdir, o->object_dir,
 			repo->commondir, "objects");
+	free(repo->alternate_db);
+	repo->alternate_db = xstrdup_or_null(o->alternate_db);
 	expand_base_dir(&repo->graft_file, o->graft_file,
 			repo->commondir, "info/grafts");
 	expand_base_dir(&repo->index_file, o->index_file,
@@ -215,6 +217,7 @@ void repo_clear(struct repository *repo)
 	FREE_AND_NULL(repo->gitdir);
 	FREE_AND_NULL(repo->commondir);
 	FREE_AND_NULL(repo->objectdir);
+	FREE_AND_NULL(repo->alternate_db);
 	FREE_AND_NULL(repo->graft_file);
 	FREE_AND_NULL(repo->index_file);
 	FREE_AND_NULL(repo->worktree);

repository.h

@@ -26,6 +26,9 @@ struct repository {
 	 */
 	char *objectdir;
 
+	/* Path to extra alternate object database if not NULL */
+	char *alternate_db;
+
 	/*
 	 * Path to the repository's graft file.
 	 * Cannot be NULL after initialization.
@@ -93,6 +96,7 @@ struct set_gitdir_args {
 	const char *object_dir;
 	const char *graft_file;
 	const char *index_file;
+	const char *alternate_db;
 };
 
 extern void repo_set_gitdir(struct repository *repo,

sha1_file.c

@@ -667,15 +667,11 @@ int foreach_alt_odb(alt_odb_fn fn, void *cb)
 
 void prepare_alt_odb(void)
 {
-	const char *alt;
-
 	if (alt_odb_tail)
 		return;
 
-	alt = getenv(ALTERNATE_DB_ENVIRONMENT);
-
 	alt_odb_tail = &alt_odb_list;
-	link_alt_odb_entries(alt, PATH_SEP, NULL, 0);
+	link_alt_odb_entries(the_repository->alternate_db, PATH_SEP, NULL, 0);
 
 	read_info_alternates(get_object_directory(), 0);
 }