runGit fails when git is not on path

[dbaynard]

This is from stack:

Exception when trying to run compile-time code:
        git: readCreateProcessWithExitCode: runInteractiveProcess: exec: does not exist (No such file or directory)
      Code: tGitInfoCwdTry

githash/src/GitHash.hs

Lines 184 to 189 in c3d3859

	runGit root args = do
	let cp = (proc "git" args) { cwd = Just root }
	(ec, out, err) <- readCreateProcessWithExitCode cp ""
	case ec of
	ExitSuccess -> return $ Right out
	ExitFailure _ -> return $ Left $ GHEGitRunFailed root args ec out err

It looks like readCreateProcessWithExitCode is throwing an exception when it can't find git. It would help to say that explicitly — perhaps by catching and rethrowing with a better error message?

Edit: This needs to be handled so tGitInfoCwdTry doesn't throw an exception.

Related: commercialhaskell/stack#4364

[snoyberg]

This should be addressed by 48f0c95, I'll drop a comment on the Stack issue. Thanks for clarifying 👍

[snoyberg]

I've made a release with the new fixes, closing.