This avoids a hang approximately 1% of the time when running the test
suite on StatelessOpenPGP.
Since I've not seen git-annex hang when running git like that, I guess
git probably does something that avoids hanging similarly. Still, fixed
the same problem in Utility.Gpg too.
Sponsored-by: Kevin Mueller on Patreon
Test a specified Stateless OpenPGP command with eg:
git-annex test --test-git-config annex.shared-sop-command=sqop
Also documented that config and another one, but so far only the test suite
uses the configs, have not yet implemented using it for actual symmetric
encryption.
Sponsored-by: Joshua Antonishen on Patreon