Add detailed info (description, source and target branch, assignee) to message.
Change subject to 'repo_name / PR #id title'.
Modify some test fixtures for better coverage.
Rename:
PUSH_COMMITS_LIMIT to COMMITS_LIMIT
PUSH_COMMIT_ROW_TEMPLATE to COMMIT_ROW_TEMPLATE
PUSH_COMMITS_MORE_THAN_LIMIT_TEMPLATE to COMMITS_MORE_THAN_LIMIT_TEMPLATE