Some custom JIRA issue key patterns not linked in activity stream

As per the JIRA Fisheye integration guide, the following steps are required for a successful linking between JIRA issue keys and Fisheye changesets:

- JIRA requires FishEye to manually refresh repository cache when repository changes are made — When a repository is removed, or when there has been any change in FishEye repositories, JIRA does not update the FishEye repository list cache automatically. You must manually refresh the repository list cache. This is done in JIRA: 'Administration' > 'FishEye Configuration' > 'Refresh Cache' link (next to 'Repository List Cache')
- FishEye doesn't check for invalid JIRA issue keys – FishEye doesn't check for invalid issue keys, such as UTF-8. An error will result if FishEye tries to connect to an issue that doesn't exist.
- FishEye doesn't recognise custom JIRA issue key formats – FishEye assumes that JIRA issue keys are of the default format for JIRA 5.0 and later: that is, up to 10 letters, followed by a hyphen and the issue number (i.e. [a-zA-Z]{10}-[0-9]+), for example FishEye-123. 

But it also seems like custom JIRA issue key patterns are supported by Fisheye afterall, as the commits with these issue keys are being linked successfully to JIRA issue and displayed under the "Source" tab in JIRA.
There is however an issue with how these JIRA issue keys are linked/rendered in Fisheye in the activity stream:

• A JIRA project key such as "ABC_DE", for example: ABC_DE-1 is being rendered as a linked URL in Fisheye activity stream and when clicked takes the user to the related JIRA issue.
• A JIRA project key such as "ABCD100_EF", for example: ABCD100_EF-1 is not being rendered as a linked URL in Fisheye activity stream and hence cannot take the user to the linked JIRA issue.
• The linked commit for both keys however is successfully listed under the "Source" tab in JIRA.

JIRA has announced end of support for custom keys other than those with digit, underscore and numbers in the keys and the above examples belong to the "supported" format. If Fisheye does not supported custom JIRA issue keys, then none of the above two should be linked in JIRA or Fisheye. If they are however supported, then we need to revise the above document and have a consistent behaviour for all custom JIRA issue keys.