There's no reason to have main directly construct
the URL. A different VCS (such as GitLab) could
have a different URL construction. Further, in the
case of LocalClient, there is no URL.
Add a new method, get_issue_url(), which returns
the VCS-specific web URL for viewing an issue.
This results in moving GitHub-specific code from
main into GitHubClient, but with no change in behavior.
This is just a safe fallback for local testing.
If environment variables which activate the
creation of the GitHub client aren't set, then
the Local client is created. It acts on the most
recent commit of the repo in the working directory.
Minor edit to GitHubClient so that it raises an
EnvironmentError exception if INPUT_GITHUB_URL
environment variable is not defined. This allows
main to detect the error and fall back to trying
to use the Local client
Split main.py into modules to (mostly) isolate the
GitHub-specific code from the general TODO
detection and program logic.
This is both for readability/maintainability and
to prepare for potentially supporting other
version control systems (e.g. GitLab, BitBucket).
