Add pin expiration system (--dev-until-next-release)

[kit-ty-kate]

Idea by @AltGr

It would be nice to add some kind of flag to a pinned package that tells opam to remove it in case a new release has been found while updating.

This feature could take the form of an option given to opam add: --dev-until-next-release.
Maybe it would be good to also add a set-expiration subcommand, as follow:

$ opam pin add pkg some-dir
$ opam pin set-expiration pkg until-next-release
$ opam pin set-expiration pkg never

[dbuenzli]

Which default would you expect ? (I would balance on until-next-release)

[kit-ty-kate]

I would say: never, to keep the backward compatibility.

[dbuenzli]

I'd argue that most people pin with the intent of until-next-release.

[dbuenzli]

Another thing to consider is that if we find a way to properly solve #2932 that would automatically happen by virtue of version comparison.

[dbuenzli]

(In the sense that you would not pin but opam install --dev)

[Drup]

I'd argue that most people pin with the intent of until-next-release.

I don't know about most people, but I know that would annoy me greatly, and would probably cause me a great deal of frustration because something that was pin is now unpinned without any instruction from me and I forgot about that feature.

So, I vote for the non-clever thing by default, and only enable the clever thing with a flag.

[dbuenzli]

@Drup I kind of agree with you, pin should be pin. I think the natural thing to do here is to eschew the concept of "pin expirations" and introduce the notion of --dev installs.

[AltGr]

A "dev" pin could actually be different in two ways:

• pin to a specific source version (e.g. a git-hash) ; or simply skip updating the pin unless explicit. Because currently pin --dev would pin to git and then update to master on every opam update, and it's not what the user would wish in this case.
• unpin as soon as a new version of the package appears, in any repository.