record Git revision in devel builds

[geekosaur]

cabal --version in such builds will include the Git commit and branch (if not master).

I've already been informed that this is not appropriate, but maybe someone will find something worth salvaging in it. It is also incomplete insofar as it needs a changelog entry and such (but probably not a test).

Consider this my last submission.

Template Α: This PR modifies behaviour or interface

Include the following checklist in your PR:

• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog.
  • Is the change significant? If so, remember to add significance: significant in the changelog file.
• The documentation has been updated, if necessary.
• Manual QA notes have been included.
• Tests have been added. (Ask for help if you don’t know how to write them! Ask for an exemption if tests are too complex for too little coverage!)

[geekosaur]

hilfy «cabal:git-revs@39b5fae1a$» Z$ $(cabal list-bin cabal) --version
cabal-install version 3.15.0.0 (commit 39b5fae on git-revs, Sun Nov 10 03:13:17 2024 -0500)
compiled using version 3.15.0.0 of the Cabal library (in-tree)

I did come up with a reasonable situation where Cabal could have different git information than cabal-install, so I added that back in. (Building a pre-release cabal-install package with a pre-release ghc, not in-tree, such that ghc's libraries/cabal is used.) I did simplify the output if it's the same, as shown above.