fix(mix/scm): handle GIT_TRACE=1

[jeffreylo]

When GIT_TRACE=1 is set in the env, mix deps.get fails with an unexpected FunctionClauseError due to git --version's output including trace output from git itself:

λ GIT_TRACE=1 mix deps.get
* Getting bar (git@github.com:foo/bar.git - main)
22:17:06.786357 git.c:476               trace: built-in: git init --quiet
22:17:06.798692 git.c:476               trace: built-in: git remote add origin git@github.com:foo/bar.git
22:17:06.804333 git.c:476               trace: built-in: git config remote.origin.url git@github.com:foo/bar.git
** (FunctionClauseError) no function clause matching in Mix.SCM.Git.parse_version/1

    The following arguments were given to Mix.SCM.Git.parse_version/1:

        # 1
        "22:17:06.809548 git.c:476               trace: built-in: git version\ngit version 2.50.1\n"

    Attempted function clauses (showing 1 out of 1):

        defp parse_version(<<"git version ", version::binary>>)

    (mix 1.18.4) lib/mix/scm/git.ex:426: Mix.SCM.Git.parse_version/1
    (mix 1.18.4) lib/mix/scm/git.ex:419: Mix.SCM.Git.git_version/0
    (mix 1.18.4) lib/mix/scm/git.ex:132: Mix.SCM.Git.checkout/2
    (elixir 1.18.4) lib/file.ex:1665: File.cd!/2
    (mix 1.18.4) lib/mix/dep/fetcher.ex:68: Mix.Dep.Fetcher.do_fetch/3
    (mix 1.18.4) lib/mix/dep/converger.ex:238: Mix.Dep.Converger.all/9
    (mix 1.18.4) lib/mix/dep/converger.ex:170: Mix.Dep.Converger.init_all/8
    (mix 1.18.4) lib/mix/dep/converger.ex:110: Mix.Dep.Converger.all/4

This patch updates git_version to handle trace noise by running parse on the final output line of git --version.

New deps.git_test added to exercise the GIT_TRACE condition.

[josevalim]

Instead of parsing it, perhaps we should force GIT_TRACE=0?

[tcoopman]

A bit off-topic, but I've had this same command fail for me, but for a different reason. The terminal printed something before the git version.

The main issue for me was that the error was very obscure and it took me a while to find why this was failing.

I've searched if there was a better way to find the git version, but apparently there isn't 🙁 so I just fixed my terminal output in the end.

[josevalim]

@tcoopman I see, so we should make this more robust in general. Sounds good.

[josevalim]

💚 💙 💜 💛 ❤️

[jeffreylo]

thank you, @josevalim