pre-commit-hooks

Fix "while scanning a plain scalar found unexpected ':'"

Add test case for valid yaml

Merge pull request #619 from m-khvoinitsky/master

forbid-new-submodules: fix triggering failure when only a submodule is committed (without any other file); support --from-ref and --to-ref; fixes #609

Merge pull request #639 from pre-commit/pre-commit-ci-update-config