Re: [PATCH v4 0/7] add symref-* commands to 'git-update-ref --stdin'

> From: Karthik Nayak <karthik.188@gmail.com>
>
> The 'git-update-ref(1)' command allows transactional reference updates.
> But currently only supports regular reference updates. Meaning, if one
> wants to update HEAD (symbolic ref) in a transaction, there is no tool
> to do so.
>
> One option to obtain transactional updates for the HEAD ref is to
> manually create the HEAD.lock file and commit. This is intrusive, where
> the user needs to mimic internal git behavior. Also, this only works
> when using the files backend.
>
> At GitLab, we've been using the manual process till date, to allow users
> to set and change their default branch. But with the introduction of
> reftables as a reference backend, this becomes a necessity to be solved
> within git.
>
> This patch series goes about introducing a set of commands
> symref-{create,verify,delete,update} to work with symrefs complimenting
> the existing commands for the regular refs in the '--stdin' mode of
> 'git-update-ref'.
>
> The 'symref-verify' command can be used to verify if a symref exists and
> its existing value.
>
> The 'symref-create' command can be used to create a new symref.
>
> The 'symref-delete' command can be used to delete an existing symref while
> optionally checking its existing value.
>
> The 'symref-update' command can be used to update a symref, create a symref,
> delete a symref or even convert an existing regular ref to a symref. Wherein
> like the regular 'update' command, the zero OID can be used to create/delete
> a symref.
>
> While this series adds the commands and the required ground work, it only
> is accessile within the '--stdin' mode of 'git-update-ref'. However, it makes
> it easy to extend it further to the command line too, which will be present
> in a follow up series.
>