We had been getting these exceptions every now and again intermittently but then the next build would be fine.

Now we are experiencing them much more frequently. Here is what is seen as the final output to the log file:

18:40:19 [xxxREPO] $ git log --raw --first-parent --format="zzREPOzz%H%n%an<%ae>%aD%n%cn<%ce>%cD%n%s%n%n%byyREPOyy" 66da983ea1516b76f1cc6a078940abd2509862f1..27ec061e06fa872f8d01dad5322534df2559d156
18:40:19 FATAL: String index out of range: -114
18:40:19 java.lang.StringIndexOutOfBoundsException: String index out of range: -114
18:40:19 at java.lang.String.substring(String.java:1949)
18:40:19 at hudson.plugins.repo.ChangeLog.generateChangeLog(ChangeLog.java:167)
18:40:19 at hudson.plugins.repo.ChangeLog.saveChangeLog(ChangeLog.java:239)
18:40:19 at hudson.plugins.repo.RepoScm.checkout(RepoScm.java:259)
18:40:19 at hudson.model.AbstractProject.checkout(AbstractProject.java:1256)
18:40:19 at hudson.model.AbstractBuild$AbstractBuildExecution.defaultCheckout(AbstractBuild.java:589)
18:40:19 at jenkins.scm.SCMCheckoutStrategy.checkout(SCMCheckoutStrategy.java:88)
18:40:19 at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:494)
18:40:19 at hudson.model.Run.execute(Run.java:1502)
18:40:19 at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
18:40:19 at hudson.model.ResourceController.execute(ResourceController.java:88)
18:40:19 at hudson.model.Executor.run(Executor.java:236)