Re: [RFC v3 3/4] submodule: Teach 'add' about a configurable local-branch

>
> @@ -339,7 +339,19 @@ module_clone()
>         echo "gitdir: $rel/$a" >"$sm_path/.git"
>
>         rel=$(echo $a | sed -e 's|[^/][^/]*|..|g')
> -       (clear_local_git_env; cd "$sm_path" && GIT_WORK_TREE=. git config core.worktree "$rel/$b")
> +       superproject_branch=$(get_current_branch)
> +       default_local_branch=$(get_submodule_config "$sm_name" local-branch)
> +       (
> +               clear_local_git_env
> +               cd "$sm_path" &&
> +               GIT_WORK_TREE=. git config core.worktree "$rel/$b" &&
> +               local_branch=$(get_local_branch "${superproject_branch}" "${default_local_branch}") &&
> +               # ash fails to wordsplit ${branch:+-b "$branch"...}
> +               case "$branch" in
> +               '') git checkout -f -q -B "$local_branch" ;;
> +               ?*) git checkout -f -q -B "$local_branch" "origin/$branch" ;;
> +               esac
> +       ) || die "$(eval_gettext "Unable to checkout submodule '\$sm_path'")"
>  }
>

>  To elaborate the idea I sketched out here [2], say
> you want:
>
>   Superproject branch  Submodule branch  Upstream branch
>   ===================  ================  ===============
>   master               master            master
>   super-feature        master            master
>   my-feature           my-feature        master
>   other-feature        other-feature     other-feature
>
> That's only going to work with per-superproject-branch configs for
> both the local and remote branches.  Using the same name for both
> local and remote branches does not work.
>
> Let me motivate each of the combinations in the above table:
>
> * master, master, master: The stable trunk.
> * super-feature, master, master: A superproject feature that works
>   with the stock submodule.
> * my-feature, my-feature, master: A superproject feature that needs an
>   improved submodule, but wants to integrate upstream master changes
>   during development.
> * other-feature, other-feature, other-feature: A superproject feature
>   that needs an improved submodule, and wants to integrate
>   other-feature changes that are also being developed upstream