A trivial script that responds to pushes that match the condition with a message. You could use it to warn about upcoming server maintenance, as users will often not open the Bitbucket user interface until they need to create a pull request:

On commit a user will see:


Counting objects: 5, done.
Writing objects: 100% (3/3), 264 bytes | 0 bytes/s, done.
Total 3 (delta 0), reused 0 (delta 0)
remote:
remote: =====================================================================
remote: Server maintenance this weekend 6AM-9AM EST!
remote:
remote: Bitbucket will be unavailable during this time,
remote: please commit locally and push when available.
remote:
remote: Sorry!
remote: =====================================================================
remote:

Another example is to remind users to do some administrative task after creating a release tag for example:

On tag:


> git tag 1.1
>
> git push --tags
Total 0 (delta 0), reused 0 (delta 0)
remote:
remote: =====================================================================
remote: You've created a tag, please be sure to to
remote: update the JIRA version.
remote: =====================================================================
remote:
To http://acme.com/bitbucket/scm/test/test.git
 * [new tag]         1.1 -> 1.1