On Wed, Jul 06, 2022 at 09:22:28AM -0400, Josh Rickmar wrote:
> Yeah, seems reasonable.  It should also skip if built with OpenSSH
> version 8.7.  From https://lore.kernel.org/git/xmqq8rxpgwki.fsf@gitster.g/:
> 
>  * In addition to GnuPG, ssh public crypto can be used for object and
>    push-cert signing.  Note that this feature cannot be used with
>    ssh-keygen from OpenSSH 8.7, whose support for it is broken.  Avoid
>    using it unless you update to OpenSSH 8.8.
> 
> I'm not aware of a way to test for this support from Git itself.  I
> guess we'll have to parse the version strings? :(
> 
> 

Either check version strings (yes, it's ugly), or do a feature test:

Try to create an SSH-signed tag with Git, and if that fails assume
support for it is nonexistent or broken.
Git has its own test suite, we can assume that their releases don't
fail for unrelated reasons when we do this sort of check.