Add missing gittaggers.py to produce timestamped version numbers.

Author: Peter Amstutz

gittaggers.py

@@ -0,0 +1,23 @@
+from setuptools.command.egg_info import egg_info
+import subprocess
+import time
+
+class EggInfoFromGit(egg_info):
+    """Tag the build with git commit timestamp.
+
+    If a build tag has already been set (e.g., "egg_info -b", building
+    from source package), leave it alone.
+    """
+    def git_timestamp_tag(self):
+        gitinfo = subprocess.check_output(
+            ['git', 'log', '--first-parent', '--max-count=1',
+             '--format=format:%ct', '.']).strip()
+        return time.strftime('.%Y%m%d%H%M%S', time.gmtime(int(gitinfo)))
+
+    def tags(self):
+        if self.tag_build is None:
+            try:
+                self.tag_build = self.git_timestamp_tag()
+            except subprocess.CalledProcessError:
+                pass
+        return egg_info.tags(self)