opam pin add <archive url> does not do anything

[kit-ty-kate]

Using opam master:

$ opam pin add https://gitlab.inria.fr/fpottier/menhir/-/archive/20211223/archive.tar.gz

No package build needed.
Nothing to do.

does not do anything. Whereas:

$ opam pin add menhir https://gitlab.inria.fr/fpottier/menhir/-/archive/20211223/archive.tar.gz

The following actions will be performed:
  ↻ recompile menhir 20211128*
Do you want to continue? [Y/n] n

does something.

[dra27]

The error message is definitely a bug (or at least it's not terribly helpful!) Ideally what's wanted is a feature that adding an archive should behave the same way as adding a git URL - scan the archive for opam files and pin them all.

[kit-ty-kate]

@rjbou reproducable with:

FROM ocaml/opam:debian-11-ocaml-4.12@sha256:40813dc1391636b4a428afbf0e678d2c81b80d9eade8a5214d8ee271fae155f3
RUN sudo ln -f /usr/bin/opam-dev /usr/bin/opam
RUN opam pin add https://gitlab.inria.fr/fpottier/menhir/-/archive/20211230/archive.tar.gz