Thank you for the clarification. No, I see no need to retain 1.6 compatibility.

It would probably help the users if the git-plugin page would mention the minimum required java version. It already mentions minimum requirements for dependencies and git runtime. Additionally, it would help developers if there would be some kind of check for minimum version. At least they wouldn't then ask the same question I did.

Git client plugin 1.17.0 released 25 Apr 2015 and includes this fix.

I've also compiled and run the git client plugin automated tests with JDK 6 and do not see any failure with JDK 6. Unfortunately, when I run the git plugin automated tests with JDK 6, it shows that there is a problem. The stack trace is:

testIsoDate(hudson.plugins.git.GitChangeSetTest)  Time elapsed: 2.798 sec  <<< ERROR!
java.lang.IllegalArgumentException: Illegal pattern character 'X'
	at java.text.SimpleDateFormat.compile(SimpleDateFormat.java:768)
	at java.text.SimpleDateFormat.initialize(SimpleDateFormat.java:575)
	at java.text.SimpleDateFormat.<init>(SimpleDateFormat.java:500)
	at java.text.SimpleDateFormat.<init>(SimpleDateFormat.java:475)
	at hudson.plugins.git.GitChangeSet.getTimestamp(GitChangeSet.java:209)
	at hudson.plugins.git.GitChangeSetTest.testIsoDate(GitChangeSetTest.java:154)

I'd prefer to not have to fix that problem, since the Jenkins project is saying goodbye to Java 6

Code changed in jenkins
User: Mark Waite
Path:
pom.xml
http://jenkins-ci.org/commit/git-client-plugin/3bd20ddf480daf6794ba2a8de54007a8894c65a1
Log:
Base 1.17.1 off 1.16.1: allow more study of git 2.3.6-SNAPSHOT issues

The release of git client plugin 1.17.0 delivered a fix for
[ISO date parsing](https://issues.jenkins-ci.org/browse/JENKINS-27097).
Unfortunately, that fix exposes a long-standing bug in git plugin versions
2.3.5 and earlier. The bug is fixed in git plugin 2.3.6-SNAPSHOT.
However, tests of git plugin 2.3.6-SNAPSHOT show that it is not yet
ready for production use.

Rather than rush to deliver git plugin 2.3.6, this change will restore the
git client plugin to the code base which was delivered with git client
plugin 1.16.1. That will hide the ISO date parsing bug that is in git
plugin 2.3.5 and earlier and allow more time to prepare 2.3.6 for release.

The 1.17.0 changes are not included in this build, including:

• Update minimum Jenkins version from 1.509 to 1.532.2
• Update JGit to 3.7.0
• [Allow prune with JGit JENKINS-26197](https://issues.jenkins-ci.org/browse/JENKINS-26197)
• [Use ISO-8601 date format in changelog JENKINS-27097](https://issues.jenkins-ci.org/browse/JENKINS-27097)
• [Improve checkout failure message JENKINS-26748](https://issues.jenkins-ci.org/browse/JENKINS-26748)
• Guard against null pointer exception in several API calls
• Update other dependencies

The git plugin and git client plugin are being tested in hopes of releasing new versions before the end of June. If you're willing to assist with the testing, please download and install a pre-release build of the git client plugin and the git plugin. Problems detected in the pre-release should be e-mailed to MarkEWaite and ndeloof.

I wrote some test ideas if you would like suggestions of areas that need testing. The git plugin supports many different use cases and its automated tests only evaluate a very few of those use cases.