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>

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;