Always show which directory is not a git repository

Unify all

  fatal: Not a git repository

error messages so they include path information.

Signed-off-by: Richard Hartmann <richih@net.in.tum.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

setup.c

@@ -468,7 +468,7 @@ const char *setup_git_directory_gently(int *nongit_ok)
 				*nongit_ok = 1;
 				return NULL;
 			}
-			die("Not a git repository");
+			die("Not a git repository (or any of the parent directories): %s", DEFAULT_GIT_DIR_ENVIRONMENT);
 		}
 		if (chdir(".."))
 			die("Cannot change to %s/..: %s", cwd, strerror(errno));