Git Repository should work with command 'git log'.

from BSP-4755

Steps to reproduce:
1) set up a Git plan, for example pointing at "git://github.com/atlassian/homebrew.git"
1.1) set up branch != "master", i.e. "atlassian-sdk"
1.2) create script task containing "git log"
2) tick "clean working directory after each build" (or "Force Clean Build" - doesn't really matter for this issue)
3) run plan (you might need to run it twice to observe the problem)
4a) build will fail with "fatal: bad default revision 'HEAD'"
4b) where expected behavior is to see git changesets in the logs of the successful build