Delete sample changelog at end of test - check for open file leak

JENKINS-20585 reports that changelog.xml cannot be deleted on Windows
because it is held busy by a process.  This test assumes that process
is Jenkins itself, and that the GitChangeLogParser.parse() method is
the most likely culprit.
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Update git-client dependency now that 1.6.0 has been released
Merge pull request #184 from MarkEWaite/master-pom-update-jgit-client-1.6.1-SNAPSHOT

Update jgit-client version in pom to git-client 1.6.1-SNAPSHOT
[JENKINS-19994] Close files opened by computeChangeLog, use new abort() method

All calls to a changelog instance must conclude with either a call to
execute() or a call to abort().  Files will be left open if one of
those two methods is not called before the changelog instance goes out
of scope.
Merge pull request #185 from MarkEWaite/JENKINS-19994-close-changelog-opened-files

[JENKINS-19994] Close files opened by computeChangeLog, use abort()
[maven-release-plugin] prepare release git-2.0.1
[maven-release-plugin] prepare for next development iteration
Merge branch 'release'

Conflicts:
	pom.xml
[FIXED JENKINS-14026] git plugin doesn't support branch name contains
slash ("/")

The main issue is to determine whether an input containing a slash is a
qualified branch (remote followed by branch name) or a branch name on
which the remote name needs to be prepended.

When there is only one remote involved, that can be solved by prepending
the remote name to the branch name if the branch name doesn't already
start with the remote name.

Note : This commit doesn't cover cases where the given branch name is a
pattern
Merge pull request #187 from jenkinsci/JENKINS-14026

[FIXED JENKINS-14026] git plugin doesn't support branch name contains
Make checkout lock failure retryable.