in TeamCity.GitHubIssues-server/src/main/java/jetbrains/buildServer/issueTracker/github/GitHubIssueFetcher.java [68:75]
private String getIssueId(@NotNull final String idString) {
final Matcher matcher = myPattern.matcher(idString);
if (matcher.find() && matcher.groupCount() > 0) {
return matcher.group(1);
} else {
return idString;
}
}