Describe never-ending job execution problem in 2.3.6-SNAPSHOT

Problem is visible in:

https://github.com/MarkEWaite/git-plugin/tree/master-alexpasca-master

That includes the git plugin commits through

jenkinsci/git-plugin@06415b9

It also includes the fix for JENKINS-28506 as represented in

jenkinsci/git-plugin#324

It also includes a minor fix from Alex Pasca:

jenkinsci/git-plugin#325

README.md

@@ -1 +1,7 @@
 [JENKINS-26197](https://issues.jenkins-ci.org/browse/JENKINS-26197) - confirm JGit prunes stale remote tracking branches correctly
+
+Shows a problem in the development version of git plugin 2.3.6.  If
+the development version polls this repository, the polling job will
+never stop building new copies of itself.
+
+The 2.3.5 plugin does not have that problem (at least in my testing).