Print git hash in version output and add -version

[Timmmm]

Hi, I've been recompiling a Sail a bit and finding Opam very confusing. It would be really helpful if sail had a sail -version option that printed the version and git hash so I know if Opam has actually built the version I want. Also add -version as an alias to -v because I only just realised that there even was a version option.

(Also make sure it doesn't require the source code to be a git repo - I've seen projects do that before and it's quite annoying because then you can't build from source tarballs.)

[Alasdair]

Currently sail -v includes the git commit number when not built using opam, i.e. when using make install (which just uses dune). If you are recompiling a lot, you can have opam only manage dependencies using opam install . --deps-only then build manually.

[Timmmm]

Ah ok, sounds like I just need to read how to use opam!

[Timmmm]

FWIW I don't think the git hash in the output is quite right - you can make install sail, then checkout a different commit, make install again and it will still show the old commit. make clean; make install updates it to the new one, so something is missing in the dependency graph.

Also I'm going to reopen this because I keep trying to run sail --version and getting shouted at! :-)

[Alasdair]

I hadn't noticed this before, but it seems dune doesn't pick up that things have changed after a git checkout. Maybe we could add dune clean as a post-commit hook, but not sure how well that would work.

[Alasdair]

Or it might be that the rule that generates the file containing the commit needs to run every build

[Alasdair]

Yes, the problem is that after git checkout the manifest.ml from the previous checkout still exists, so the build rule:

(rule
  (target manifest.ml)
  (mode fallback)
  (action
    (with-outputs-to %{target}
      (chdir %{workspace_root}
        (run sail_manifest -gen_manifest)))))

doesn't fire

I think everything else should be fine, just the version info will be incorrect until a dune clean is run.