Add isBareRepository tests

The assertions are intended to detect unintentional changes to a
deprecated API.  It is safe to assume that since the API is
deprecated, its behavior should not change with future plugin
releases.

The JGit implementation attempts to match the CliGit implementation
but doesn't quite match.  The prioritization of assertions in this file
attempts to show the most critical use cases for isBareRepository are
covered in JGit and CliGit with similar results.

The Javadoc for the CliGit implementation at one time stated that
its argument must be the ".git" directory.  If the caller passes
the .git directory (for a working directory) or the root directory
of the repository (for a bare repository), then the JGit and CliGit
implementations return consistent results.

Fix WorkingArea repo() method for bare repo
Change JGit.isBareRepository to be more consistent with CliGit

Only use .git directory in isBare if it actually exists

If GIT_DIR is not absolute, use workspace as repository
Pass submodule reset as a single argument to foreach
Merge pull request #118 from tgyurci/master

Pass submodule reset as a single argument to foreach
Remove unused imports
Update to latest apache httpcomponents - 4.3.3
Add a few assertions, use explicitly typed collection in test
Use explicitly typed list in JGitAPIImpl
Removed unused imports
ObjectID's should be same, not Ref's - Fix broken unit test assertion
Use Jenkins 1.509, match with git-plugin

1.509 is also needed for credentials tests
Remove maven source properties, either inherit from parent or accept default

JDK 1.5 is no longer supported by Oracle.
Additional tests of wildcards in call to getHeadRev()

Exploring change proposed for JENKINS-20767
Correct test internal behavior to match variable name

The variable name "wildOrigin" was chosen intentionally for the case
that was being tested, but then I made a mistake in later experiments
and changed the test without changing the variable name.
Merge pull request #119 from MarkEWaite/master-sync-jenkins-dependency-with-git-plugin

Sync jenkins dependency with git plugin
Added test for getHeadRev for branches with namespace
Fix for getHeadRev bug when using branch namespaces

JENKINS-20767
Apply PR feedback: Style, imports + missing fix for JGitAPIImpl
Switched back to "jenkinsci" to be on safe side

The tests will fail now until the required branches are
available in jenkinsci! For local tests you can switch
"jenkinsci" to "alexanderlink".

You have to decide how to handle tests!
Currently the productive repo is cloned for testing...
Changed test branches from "test/..." to "tests/..."

+ small refactoring