Git SSH/GPG signing flags and config

[Fabian Stelzer <fs@gigacodes.de>]

Hi everyone,
the `signing git objects with ssh` series was released with 2.34 and i'd 
like to thank everyone for your support and the good reviews!
I think it would be beneficial now to adjust some of the wording in flags 
and the config. Currently everything is configured via gpg.* and all the 
`please sign this` flags are named --(no-?)gpg-sign.
I would be in favor of a more generic flag independent of the signing 
mechanism. Adding something like `--ssh-sign` would suggest that you'd be 
able to switch signing format with it which i think would not be terribly 
useful. If you need to use multiple signing mechanism those would usually be 
configured per repository and can easily be done with an `includeif gitdir:` 
in your config.
Therefore i would suggest just adding a generic `--(no-?)sign` to all the 
commands that support gpg-sign right now. The only problem i see is a 
conflict with `--signoff` so i'm open to other naming ideas. The same goes 
for the config. `sign.` as an alias to `gpg.` would work well with the 
current settings.
Let me know what you think and i could prepare a first patch for one command 
to see what the alias / config / docs change could look like.

Best regards,
Fabian