Re: [PATCH v2 1/2] ssh signing: support non ssh-* keytypes

>On Thu, Nov 18, 2021 at 12:14 PM Fabian Stelzer <fs@gigacodes.de> wrote:
>> The user.signingKey config for ssh signing supports either a path to a
>> file containing the key or for the sake of convenience a literal string
>> with the ssh public key. To differentiate between those two cases we
>> check if the first few characters contain "ssh-" which is unlikely to be
>> the start of a path. ssh supports other key types which are not prefixed
>> with "ssh-" and will currently be treated as a file path and therefore
>> fail to load. To remedy this we move the prefix check into its own
>> function and introduce the prefix `key::` for literal ssh keys. This way
>> we don't need to add new key types when they become available. The
>> existing `ssh-` prefix is retained for compatibility with current user
>> configs but removed from the official documentation to discourage its
>> use.
>
>I think we usually avoid removing documentation for something which is
>still supported (even if deprecated) for the very real reason that
>people will still encounter the old form in the wild, whether in
>configuration files, in blogs, or elsewhere, and may be perplexed to
>discover that the form is not documented (thus not understand how or
>why it seems to be working). Instead, we can discourage its use by
>mentioning clearly that it is deprecated and that `key::` should be
>used instead.
>

>> Signed-off-by: Fabian Stelzer <fs@gigacodes.de>
>> ---
>> diff --git a/Documentation/config/user.txt b/Documentation/config/user.txt
>> @@ -36,10 +36,10 @@ user.signingKey::
>>         This option is passed unchanged to gpg's --local-user parameter,
>>         so you may specify a key using any method that gpg supports.
>> -       If gpg.format is set to "ssh" this can contain the literal ssh public
>> -       key (e.g.: "ssh-rsa XXXXXX identifier") or a file which contains it and
>> -       corresponds to the private key used for signing. The private key
>> -       needs to be available via ssh-agent. Alternatively it can be set to
>> -       a file containing a private key directly. If not set git will call
>> -       gpg.ssh.defaultKeyCommand (e.g.: "ssh-add -L") and try to use the first
>> -       key available.
>> +       If gpg.format is set to `ssh` this can contain the path to either
>> +       your private ssh key or the public key when ssh-agent is used.
>> +       Alternatively it can contain a public key prefixed with `key::`
>> +       directly (e.g.: "key::ssh-rsa XXXXXX identifier"). The private key
>> +       needs to be available via ssh-agent. If not set git will call
>> +       gpg.ssh.defaultKeyCommand (e.g.: "ssh-add -L") and try to use the
>> +       first key available.
>
>Thus, perhaps this text could end with:
>
>    For backward compatibility, a raw key which begins with "ssh-",
>    such as "ssh-rsa XXXXXX identifier", is treated as "key::ssh-rsa
>    XXXXXX identifier", but this form is deprecated; use the `key::`
>    form instead.