Re: [PATCH v3 4/6] worktree: new config file hierarchy

>> With this patch, since worktree v1, the repo config file (or worktree
>> config file in multi worktree context) is no longer shared. Main
>> worktree reads $C/config.  Linked worktrees read $C/worktrees/xxx/config
>> and a new file, $C/worktrees/config. Sharing is done via this new
>> file. The read hierarchy for a worktree becomes
>>
>> 1) system config
>> 2) XDG config
>> 3) user config
>> 4) $C/common/config
>> 5) $C/worktrees/xxx/config (or $C/config for main worktree)
>>
>> Compare to an alternative scheme where $C/config contains both shared
>> variables and main-worktree-only ones, this is a cleaner design.
>>
>> * We do not have to check every single variable name to see if it's
>>   shared or per-worktree when reading config files.
>>
>> * We do not enforce any particular variable split. If a variable
>>   is in $C/worktrees/config, it is shared. Putting core.worktree in
>>   $C/worktrees/config is punished the same way the variable is put in
>>   $HOME/.gitconfig, for example.
>>
>> * We will provide a new "git config --repo" to access this new config
>>   file. In single-worktree context, or worktree v0, --repo is an alias
>>   of --local.
>>
>> There is one problem though. We store worktree version in config file
>> and expect that all worktrees must share the same version (i.e. read
>> the same config file). But the share-ness of per-repo config files is
>> changed based on worktree version. Where do we put extensions.worktree
>> then?
>
> I cannot see why it cannot live in $C/common/config, which would be
> read as the fourth alternative in your earlier enumeration.  What I
> am missing?