guix: make it possible to override gpg binary

[prusnak]

For example on Qubes OS one might want to use qubes-gpg-client-wrapper instead

Fixes #24346

[JeremyRand]

Concept ACK. Regarding the lint failure about not quoting the new variable, I am unsure whether this lint failure is actually a problem. It seems to me that some users may wish to pass extra arguments to whatever executable is used in place of gpg; quoting the variable would prevent this use case. Thoughts?

[prusnak]

It seems to me that some users may wish to pass extra arguments to whatever executable is used in place of gpg; quoting the variable would prevent this use case.

If we want to enable passing the extra arguments, we'd need to do the following change, so the check_tools correctly extracts the binary name and checks against that.

- check_tools ${GPG}
+ GPG_ARRAY=($GPG)
+ check_tools "${GPG_ARRAY[0]}"

If we want to disable passing the extra arguments, it's enough to just quote the variable usage, right.

I will wait for resolution which way we want to go and then I'll update the PR.

[JeremyRand]

I have a weak preference for allowing extra arguments, but I do not have any immediate need for it myself, so will defer if anyone else has a good reason not to.

[prusnak]

I have a weak preference for allowing extra arguments

Applied the improvement from #24552 (comment) in e368c03e6eee2d25f4db6af606108a9dc1ca4963

If there is a consensus we do not want $GPG to contain extra arguments, I will gladly rework the PR

[theStack]

Concept ACK

[laanwj]

Concept and code review ACK af74e06

I think passing extra arguments to gpg is a valid usecase. Though, as of course always with shell nonsense, this interferes with using spaces in filenames. But that's probably not too common (sigh)…