Add option to retrieve credentials without git sync

[meissa331]

Summary

We use gopass in direnv to inject credentials. An option to ommit git sync in order to speed up the direnv script would be great :-)

Steps To Reproduce

See https://repo.prod.meissa.de/meissa/build#try-out for an example.

[dominikschulz]

Autosync should generally only run if gopass is running in a terminal: https://github.com/gopasspw/gopass/blob/master/internal/action/sync.go#L52

But if that doesn't work for some reason you could either try calling gopass config core.autosync false first or set the (deprecated) enviornment variable GOPASS_NO_AUTOSYNC to true.

[jerger]

I assume execution in direnv counts as interactive & terminal as this is executed in bashrc context.

I will try out the config and hope to observe a speedup in execution - thx for the hint :-)