Refactor list of of repo-local env vars

Move the list of GIT_* environment variables that are local to a
repository into a static list in environment.c, as it is also
useful elsewhere. Also add the missing GIT_CONFIG variable to the
list.

Make it easy to use the list both by NULL-termination and by size;
the latter (excluding the terminating NULL) is stored in the
local_repo_env_size define.

Signed-off-by: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -388,6 +388,15 @@ static inline enum object_type object_type(unsigned int mode)
 #define GIT_NOTES_REF_ENVIRONMENT "GIT_NOTES_REF"
 #define GIT_NOTES_DEFAULT_REF "refs/notes/commits"
 
+/*
+ * Repository-local GIT_* environment variables
+ * The array is NULL-terminated to simplify its usage in contexts such
+ * environment creation or simple walk of the list.
+ * The number of non-NULL entries is available as a macro.
+ */
+#define LOCAL_REPO_ENV_SIZE 8
+extern const char *const local_repo_env[LOCAL_REPO_ENV_SIZE + 1];
+
 extern int is_bare_repository_cfg;
 extern int is_bare_repository(void);
 extern int is_inside_git_dir(void);

connect.c

@@ -607,18 +607,8 @@ struct child_process *git_connect(int fd[2], const char *url_orig,
 		*arg++ = host;
 	}
 	else {
-		/* remove these from the environment */
-		const char *env[] = {
-			ALTERNATE_DB_ENVIRONMENT,
-			DB_ENVIRONMENT,
-			GIT_DIR_ENVIRONMENT,
-			GIT_WORK_TREE_ENVIRONMENT,
-			GRAFT_ENVIRONMENT,
-			INDEX_ENVIRONMENT,
-			NO_REPLACE_OBJECTS_ENVIRONMENT,
-			NULL
-		};
-		conn->env = env;
+		/* remove repo-local variables from the environment */
+		conn->env = local_repo_env;
 		conn->use_shell = 1;
 	}
 	*arg++ = cmd.buf;

environment.c

@@ -63,6 +63,23 @@ static char *work_tree;
 static const char *git_dir;
 static char *git_object_dir, *git_index_file, *git_refs_dir, *git_graft_file;
 
+/*
+ * Repository-local GIT_* environment variables
+ * Remember to update local_repo_env_size in cache.h when
+ * the size of the list changes
+ */
+const char * const local_repo_env[LOCAL_REPO_ENV_SIZE + 1] = {
+	ALTERNATE_DB_ENVIRONMENT,
+	CONFIG_ENVIRONMENT,
+	DB_ENVIRONMENT,
+	GIT_DIR_ENVIRONMENT,
+	GIT_WORK_TREE_ENVIRONMENT,
+	GRAFT_ENVIRONMENT,
+	INDEX_ENVIRONMENT,
+	NO_REPLACE_OBJECTS_ENVIRONMENT,
+	NULL
+};
+
 static void setup_git_env(void)
 {
 	git_dir = getenv(GIT_DIR_ENVIRONMENT);