Git polling depends on ‘last built’ revision. If the Jenkins job is triggered manually on different branch (detached head), the polling may result in No changes.

WE have a Job which polls for changes every 5 mins. The branch is mentioned using a Parametrized plugin. Like,

String parameter:
name: GIT_COMMIT_TAG
default: master

The polling works fine. But when I run the job manually and set GIT_COMMIT_TAG to different value (which is detached head) the subsequent polling says "No changes" to build. The polling log says,

Started on Feb 25, 2014 12:00:20 AM
Using strategy: Default
[poll] Last Built Revision: Revision 48c7cfd0bfd024abcf4e93142a78a019db0279aa (detached)
Fetching changes from the remote Git repositories
Fetching upstream changes from origin
Polling for changes in
Done. Took 1.9 sec
No changes

Git polling in this case will only start working after manual trigger of target branch 'master'