[git] convert & fix GitMergeTest
[git] rename test to what it actually tests
[git] remove some obsolete test
[git] Fixing GitRebaserReorderCommitsTest
[vcs tests] remove code duplication: move some methods to VcsTestUtil
[vcs tests] move some static utility methods to VcsTestUtil
remove unused
[git] convert & fix GitChangeProviderTests
[git] remove some obsolete tests
[git] simplify tests dir structure
[git] various tests fixes
[git] cleanup
[git] fix change provider tests: operate on io.Files for setup + more
[git] GitSingleRepoTest for tests that operate with 1 and only 1 repo
[git] fix GitBranchWorkerTest: less groovy
[git] Fix GitCrlfProblemsDetectorTest: less mocky
[git] Fix retrial if index.lock error happens.

Introduce special king of exception which allows to retrieve the output.
[git] temporary disable several tests

to be fixed later.
[git] fix reference to executable
IDEA-123011 Rebase strategy fixed in case updating without local commits