1. add a message "Polling ignores commits with certain messages"

   .*\[maven-release-plugin\].*

1. commit with this message - polling doesn't ignore the message
2. Reason: the commit message string contains a final line break (commits I created locally, commits that are created on Jenkins host with CentOS)
3. Analysis: I added some lines with listener.getLogger().println("[ABC] ...") to src/main/java/hudson/plugins/git/extensions/impl/MessageExclusion.java
4. Polling Log showed me that the message contains a line break that doesn't match with pattern - empty line in polling log:

     [ABC] Checking commit 4b22f7aacbf22359c46adbdf20b04c09cf8b890e: Found message [maven-release-plugin]
   
     [ABC]  >> excludedMessage: [.*\[maven-release-plugin\].*]
     [ABC]  >>>> Pattern IS set: .*\[maven-release-plugin\].*
     [ABC]  >> acceptedMessage: [[maven-release-plugin]
   ]

1. Fix: I changed the following line in src/main/java/hudson/plugins/git/extensions/impl/MessageExclusion.java:

     // old line that doesnt ignore the message
     excludedPattern = Pattern.compile(excludedMessage);
     // new line that works with the final line break
     excludedPattern = Pattern.compile(excludedMessage, Pattern.DOTALL);
     

As I'm not a software developer, I'm not sure about side effects when adding Pattern.DOTALL to the code line I mentioned - but it works for me with simple patterns like .[maven-release-plugin].