fix some backward compatibility bugs in `GIT_REV`

[geekosaur]

It was incorrectly displaying (in-tree) when there was no git information. Also, the spacing was slightly incompatible with older versions.

This should restore 100% compatibility with older versions of cabal-install, for scripts that parse cabal --version output.

---

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[geekosaur]

QA notes:

Build cabal for release (cabal --project-file=cabal.release.project build cabal). Run the following: (assumes you have cabal-3.14.2.0 and cabal-3.16.0.0 installed via e.g. ghcup)

hilfy Z$ cabal-3.14.2.0 --version | sed 's/$/~/'
cabal-install version 3.14.2.0~
compiled using version 3.14.2.0 of the Cabal library ~
hilfy Z$ cabal-3.16.0.0 --version | sed 's/$/~/'
cabal-install version 3.16.0.0 ~
compiled using version 3.16.0.0 of the Cabal library (in-tree)~
hilfy Z$ $(cabal list-bin cabal) --version | sed 's/$/~/' 
cabal-install version 3.17.0.0~
compiled using version 3.17.0.0 of the Cabal library ~

3.14.2.0 is the original output. (I assume the extra space crept in when the Cabal library version was added.) 3.16.0.0 is the buggy output. The final one is the fixed output; it should match 3.14.2.0 aside from the reported versions, in particular in the final spaces. Note that 3.16.0.0 has both (in-tree) and an extra space at the end of the first line.

[mergify[bot]]

Merge Queue Status

✅ The pull request has been merged at 519432fcab8c0892f80efa46160114129c49eadd

This pull request spent 2 hours 16 minutes 30 seconds in the queue, including 2 hours 5 minutes 58 seconds running CI. The checks were run on draft #11359.

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[geekosaur]

A bit belatedly, this is WRT https://github.com/haskell/cabal/issues/11340#issuecomment-3647017147.