The JDK project expects bug IDs to be exactly 7 digits with no prefix. This is enforced by `hg jcheck` today. The regex pattern used by the Skara tooling to determine what is a valid Bug ID is more relaxed in that it allows an optional prefix (e.g., JDK- or FOO123-), followed by 1 or more digits. This pattern is in a global variable, and is not configurable:

vcs/src/main/java/org/openjdk/skara/vcs/openjdk/CommitMessageSyntax.java:
    public static final Pattern ISSUE_PATTERN = Pattern.compile("((?:[A-Z][A-Z0-9]+-)?[0-9]+): (\\S.*)$");

The JDK project would likely prefer to use a pattern more like this:
    "([124-8][0-9]{6}): (\\S.*)$"

Otherwise we will lose the check for too-few vs too-many digits that is there now (it would be too easy to miss the fact that there are 6 or 8 digits by visual inspection).

If this were configurable, then each project could define their own rules (with jdk and jfx using the more restrictive rules).