Added git information to version string

Running ansible --version now outputs git information when the
repo lives in .git in the root of the ansible source (coping with the case
where the git info is elsewhere is left as an exercise).

This uses gitpython where installed, otherwise it interrogates the files
in the .git directory to get the same information.

The gitpython path could be removed, but then people might ask 'why did
you do it like this when gitpython exists'

lib/ansible/utils.py

@@ -39,6 +39,12 @@ try:
 except ImportError:
     from md5 import md5 as _md5
 
+try:
+    import git
+    HAS_GIT = True
+except ImportError:
+    HAS_GIT = False
+
 ###############################################################
 # UTILITY FUNCTIONS FOR COMMAND LINE TOOLS
 ###############################################################
@@ -287,6 +293,32 @@ def default(value, function):
         return function()
     return value
 
+def _gitinfo():
+    ''' returns a string containing git branch and commit id 
+    using gitpython if installed and native file operations if not '''
+    result = None
+    repo_path = os.path.join(os.path.dirname(__file__), '..', '..', '.git')
+    if os.path.exists(repo_path):
+        if HAS_GIT:
+            repo = git.Repo(repo_path)
+            head = repo.head
+            branch = head.reference.name
+            commit = head.commit.hexsha[:10]
+        else:
+            with open(os.path.join(repo_path, "HEAD")) as f:
+                branch = f.readline().split('/')[-1].rstrip("\n")
+            with open(os.path.join(repo_path, "refs", "heads", branch)) as f:
+                commit = f.readline()[:10] 
+        result = "({0}) [{1}]".format(branch, commit)
+    return result
+
+def version(prog):
+    result = "{0} {1}".format(prog, __version__)
+    gitinfo = _gitinfo()
+    if gitinfo:
+        result = result + " {0}".format(gitinfo)
+    return result
+
 ####################################################################
 # option handling code for /usr/bin/ansible and ansible-playbook
 # below this line
@@ -301,7 +333,7 @@ class SortedOptParser(optparse.OptionParser):
 def base_parser(constants=C, usage="", output_opts=False, runas_opts=False, async_opts=False, connect_opts=False):
     ''' create an options parser for any ansible script '''
 
-    parser = SortedOptParser(usage, version="%prog " + __version__)
+    parser = SortedOptParser(usage, version=version("%prog"))
     parser.add_option('-v','--verbose', default=False, action="store_true",
         help='verbose mode')
     parser.add_option('-f','--forks', dest='forks', default=constants.DEFAULT_FORKS, type='int',