Re: [PATCH] gpg-interface: allow selecting key id with env variable

[Junio C Hamano <gitster@pobox.com>]

Marco Beck <mbeck@eaddrinuse.net> writes:

> This allows selecting the gpg(1) key id to use for signing by setting the
> environment variable GIT_GPG_SIGNINGKEY.

Can you explain why we want to add another way to specify the key?
It appears to me that user.signingkey is an adequate "set it once,
forget it, and keep using it" way to do so.  "I cannot write to the
config file" is unlikely, as the user must be capable of writing
into the repository to sign in the first place.

Is the driving motivation "I want to sign under a different identity
from the one the repository specifies in its local configuration"?
Wouldn't that be covered with a single-shot configuration syntax:

    $ git -c user.signingkey=mbeck@eaddrinuse.net tag -s ...

Unless there is a good reason to (and these days there aren't that
many), we prefer not to add new environment variables like this.

Thanks.