Add opam pin remove --all

[kit-ty-kate]

I often find the need to clean all pins from the current switch i am working on, be it because the pin packages have all been released or other reasons, and listing all the packages or repos one by one can be extremely tedious.

[avsm]

Yes please! I also have the case that it's difficult to undo an opam install's pins

opam install .
# proceeds to pin all the local packages
# how do i undo the previous command? opam remove doesn't unpin them.

[kit-ty-kate]

Could you open a new issue to track that problem?

[kit-ty-kate]

All done

[dra27]

Tiny tweak to the message.

More importantly, -a has a lot of different meanings across opam already, so this doesn't technically make things that much worse, however opam remove -a removes automatically-installed packages but opam pin remove -a would now mean remove all pins. Might it be worth either using a different letter (opam admin already has -A for a --all option) or just not having a short form at all for this one?

[avsm]

I'm not convinced we need this PR because:

1. opam pin remove -a has a different meaning from opam remove -a (as @dra27 notes)
2. opam pin remove $(opam pin -s) accomplishes what this PR does -- we could document this.
3. opam pin install and opam pin remove are not currently symmetric, and there's no easy way to do this.

I'd recommend not adding more CLI options to opam when there are existing unix-style solutions that work, and focussing on fixing the really rough edges like 3) above which is hard to do (as you cannot easily probe the set of locally pinned packages without some wildcard magic)

[rjbou]

Should we add a word about this command being a no-op on other pin commands ?

[kit-ty-kate]

I chose to make the use of --all outside of remove without any parameter an error instead. Does that work for you?

[rjbou]

good for me!