bin(git-fetch-branch): Handle running within working directory

bin/git-fetch-branch

@@ -4,6 +4,8 @@ export USAGE='<branch>
 or: <remote> <branch>
 '
 
+cd "$(git rev-parse --show-toplevel)"
+
 # This is the recommended pattern from `man git-sh-setup`.
 #
 # shellcheck disable=SC1090
@@ -23,7 +25,6 @@ case "$#" in
     *) usage ;;
 esac
 
-
 # I often change the fetch refmap to only watch my development branches and
 # permanent shared ones. Explicitly use a default-ish refmap to undo that and
 # make this create a named local branch.