Pull in some pre-PR testing changes

Need to test these regex changes pretty heavily before merging, so might
as well start even before opening a PR.

Also reverted back to the 0.2.0a7 state of the commit-link handler
pluralization code, since the extra parentheses weren't actually needed.

sopel_modules/github/github.py

@@ -44,11 +44,18 @@
 
 '''
 
-issueURL = (r'https?://(?:www\.)?github.com/([A-z0-9\-_]+/[A-z0-9\-_]+)/(?:issues|pull)/([\d]+)(?:#issuecomment-([\d]+))?')
-commitURL = (r'https?://(?:www\.)?github.com/([A-z0-9\-_]+/[A-z0-9\-_]+)/(?:commit)/([A-z0-9\-]+)')
+# GitHub enforces alphanumeric usernames, and allows only one punctuation character: hyphen ('-')
+# Regex copied and slightly modified to meet our needs from CC0 source:
+# https://github.com/shinnn/github-username-regex/blob/0794566cc10e8c5a0e562823f8f8e99fa044e5f4/module.js#L1
+githubUsername = r'[a-z\d](?:[a-z\d]|-(?=[a-z\d])){0,38}'
+# not from anywhere, but handy to simply reuse
+githubRepoSlug = r'[A-Za-z0-9\.\-]+'
+# lots of regex and other globals to make this stuff work
+issueURL = (r'https?://(?:www\.)?github.com/({username}/{repo})/(?:issues|pull)/([\d]+)(?:#issuecomment-([\d]+))?'.format(username=githubUsername, repo=githubRepoSlug))
+commitURL = (r'https?://(?:www\.)?github.com/({username}/{repo})/(?:commit)/([A-z0-9\-]+)'.format(username=githubUsername, repo=githubRepoSlug))
 regex = re.compile(issueURL)
 commitRegex = re.compile(commitURL)
-repoRegex = re.compile('github\.com/([^ /]+?)/([^ /]+)/?(?!\S)')
+repoRegex = re.compile(r'github\.com/({username})/({repo})/?(?!\S)'.format(username=githubUsername, repo=githubRepoSlug))
 sopel_instance = None
 
 
@@ -188,7 +195,7 @@ def commit_info(bot, trigger, match=None):
         str(data['stats']['total']),
         ' changes in ',
         str(file_count),
-        (' file' if file_count == 1 else ' files')
+        ' file' if file_count == 1 else ' files'
     ]
     bot.say(''.join(response))