See issue #2471

This fixes get_remote_head() to be smarter about how to check remote
head.  It checks if it is a remote branch or tag and then checks for the
remote object id associated with it.  If it is sha1, get_remote_head()
returns it as-is since there doesn't appear to be a way to check a
remote repository for a specific object/sha1.  is_remote_tag() is added
to help out the new functionalit in get_remote_head().

In main(), if check_mode is true and version is a sha1, the module now
checks to see if the object is present.

Related to issue #2114.  This hooks in check_mode to git module.  This
will exit with changed=True at the following places:

* If the repo has not been cloned
* If the destination has local modifications, this will exit with
  changed=True.  This is because reset() will exit anyways if there are
  local mods and force is False.
* If the remote HEAD commit id is not the same as that of the local HEAD.
  This is determined by get_remote_head() that runs 'git ls-remote' to
  determine remote HEAD.

Lastly, if this is run with check_mode enabled, this will exit with
changed=False before fetch() is invoked so that no local mods are made.

Both modules seboolean and zfs have not been adapted since they defer from the default (either by having a 'null' or special state, or prefering "on"/"off" for state indication.

If a relative path is passed as an argument, this change first
converts it to an absolute path.

This fixes a bug where the git module would attempt to chdir into an
invalid directory because of multiple chdir calls against a relative
path.

* Rename fail_on_rc_non_zero to check_rc, much more succinct.
* Simplify method defintion
* Fix command module and drop shell=shell option; whether to use
  shell is determined by if args is a list.

This updates apt, apt_repository, command, cron, easy_install, facter,
fireball, git, group, mount, ohai, pip, service, setup, subversion,
supervisorctl, svr4pkg, user, and yum to take advantage of run_command
in module_common.py.

Without read permission to the current working directory, git-clone will
fail:
root@host:~$ sudo -u git -H git clone \
  git://github.com/ansible/ansible.git /home/git/ansible
fatal: Could not change back to '/root': Permission denied

This commit ensures that the working directory is changed to the
parent-folder of the destination before doing the clone.

Move operations that are dependant on a remote branch under a if
is_remote_branch() conditional.  While at it, remove assignment to cmd
string in same block that wasn't used when calling _run().

The git module would not pull in updates to a branch when
version=<branch>.  This updates that block to checkout the branch
and then do a git reset --hard <remote>/<branch>.  This
should now track updates to a branch.

Rewrote switch_version() to read .git/HEAD to find branch associated
with HEAD.  If in a detached HEAD state, will read
.git/refs/remotes/<remote>/HEAD.

Rename pull() to fetch().  It does a git fetch and then a
git fetch --tags.
Add _run() method to handle all subprocess.Popen calls.  Change
all previous calls to subprocess.Popen to use _run().

 - added terse syntax to modules.rst
 - added description of special variables to template module

Detect when on a 'no branch' branch.  If so, checkout the HEAD branch
as reported by 'git remote show <remote>'.  That should put the repo
back on a branch such that git can then merge changes as necessary.
In addition, removed hard-coded references to origin and replaced
with remote var.

Check rc instead of parsing for errors.  This now catches the case where the remote branch has been deleted and you're still trying to pull against it.

added force option to git - made both subversion and git default to force=true for backward compatibility with git's previous behavior

git module used to check stderr for the string 'error' after calling
switch_version().  This changes that to just look at the return code to
determine whether the command failed.  If the rc is not zero, the git
module will call fail_json().

The problem is that git checkout will summarize the commit message,
such as:

    HEAD is now at ea38409... removing artificial error

When the string 'error' is the commit message, this check will
erroneously think the command failed.

This also removes the method switchLocalBranch() since it is no longer
used.

whitespace + remove deprecated YAML parser (migration script lives in examples/scripts and warning was added
in 0.6 release)

Add encoding lines to python modules such that they can take unicode options if they are fed them, since the
AnsibleModule stuff no longer base64 encodes for simplicity and speed reasons.

* module.fail_json *must* have msg argument
Using http://github.com/ rather than git://github.com/ as it gets through more
firewalls

Port the file module over to the new common code infrastructure + cleanup some redundant imports since the module code already imports those things.

Convert git module to module magic.
Drop cruft no longer needed.
Standardize indent to 4 spaces in methods switchLocalBranch, reset,
clone, and get_version.
Update is_local_branch to also handle '* branch' format.
Add is_current branch method()
Update pull() method to use is_current_branch()