I had to flag some revisions to not undergo check-commit scrutiny
today to get the tests to pass, because they renamed files that had
existing failures which we're not cleaning up. Let's prevent that in
the future by using the extended git diff format to elide moved code.
Allow bypassing test-check-commit runs by specifying '# no-check-commit'
in the description. This should be avoided but is useful for upstream
imports such as pywatchman which will cause check-code to fail otherwise.
We had them on 'test-check-code-hg.t' to avoid collision with the test checking
'check-code' itself. Now that this one have been rename, we can safely remove
this suffix for all of them. This get them in line with 'check-pyflakes.t'.
