Module function git.commit threw an exception when there is nothing to commit

Description of Issue/Question

If there is nothing to commit in the path to the git checkout, I get the following exception error when applying the state.

----------
          ID: git-commit
    Function: module.run
        Name: git.commit
      Result: False
     Comment: Module function git.commit threw an exception. Exception: Command 'git commit -m commited by SaltStack' failed
     Started: 10:24:52.712617
    Duration: 10.998 ms
     Changes:
----------

whereas if I run the "git commit -m message" command directly on the minion in the path to the git checkout, it would not fail and just returns:

On branch master
nothing to commit, working directory clean

Setup

contents of SLS file:

init-git:
  module.run:
    - name: git.init
    - cwd: /path/to/repo/
    - unless: ls /path/to/repo/.git

git-set-url:
  module.run:
    - name: git.remote_set
    - cwd: /path/to/repo/
    - remote: origin
    - url: #url to the git repository
    - https_user: username
    - https_pass: {{ pillar['password'] }}
    - onchanges:
      - module: init-git

git-fetch:
  module.run:
    - name: git.fetch
    - cwd: /path/to/repo/
    - remote: origin

git-pull:
  module.run:
    - name: git.pull
    - cwd: /path/to/repo/
    - opts: 'origin master'

git-add:
  module.run:
    - name: git.add
    - cwd: /path/to/repo/
    - filename: /path/to/repo/
    - remote: origin
    - opts: '-A'

git-commit:
  module.run:
    - name: git.commit
    - cwd: /path/to/repo/
    - message: "committed by SaltStack"
    - ignore_retcode: True

git-push:
  module.run:
    - name: git.push
    - cwd: /path/to/repo/
    - remote: origin
    - ref: master
    - branch: master

Steps to Reproduce Issue

1. have a repository to commit to it
2. run the SLS against a minion

Versions Report

Salt Version:
           Salt: 2016.3.2

Dependency Versions:
           cffi: Not Installed
       cherrypy: Not Installed
       dateutil: 1.5
          gitdb: Not Installed
      gitpython: Not Installed
          ioflo: Not Installed
         Jinja2: 2.7.2
        libgit2: Not Installed
        libnacl: Not Installed
       M2Crypto: Not Installed
           Mako: 0.9.1
   msgpack-pure: Not Installed
 msgpack-python: 0.4.6
   mysql-python: 1.2.3
      pycparser: Not Installed
       pycrypto: 2.6.1
         pygit2: Not Installed
         Python: 2.7.6 (default, Oct 26 2016, 20:30:19)
   python-gnupg: Not Installed
         PyYAML: 3.10
          PyZMQ: 14.0.1
           RAET: Not Installed
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.2.1
            ZMQ: 4.0.5

System Versions:
           dist: Ubuntu 14.04 trusty
        machine: x86_64
        release: 3.13.0-105-generic
         system: Linux
        version: Ubuntu 14.04 trusty

Start at the Salt git.commit module entry point and reproduce the SLS case in a repository with no changes. Compare its handling of Git's clean-working-tree result with the direct command; done means applying the state no longer reports an exception when there is nothing to commit.