store git commit hash to build.source

Git HEAD commit hash is now stored in build.info field. this field is
currently used by content generators, but not by other builds. Also
original checked out url is stored in build.extra.url field.

Fixes: https://pagure.io/koji/issue/550

koji/daemon.py

@@ -32,6 +32,7 @@ import urlparse
 from fnmatch import fnmatch
 import base64
 import time
+import subprocess
 import sys
 import traceback
 import errno
@@ -501,9 +502,28 @@ class SCM(object):
                 rel_path = '../' * len(path_comps.split('/'))
                 os.symlink(rel_path + 'common', '%s/../common' % sourcedir)
 
+        self.sourcedir = sourcedir
         return sourcedir
 
 ## END kojikamid dup
+    def get_source(self):
+        r = {
+            'url': self.url,
+            'source': '',
+        }
+        if self.scmtype.startswith('GIT'):
+            cmd = ['git', 'rev-parse', 'HEAD']
+            fragment = subprocess.check_output(cmd, cwd=self.sourcedir).strip()
+            scheme = self.scheme[:-3]
+            if self.user:
+                netloc = '%s@%s' % (self.user, self.host)
+            else:
+                netloc = self.host
+            path = self.repository
+            query = self.module
+            r['source'] = urlparse.urlunsplit([scheme, netloc, path, query, fragment])
+        return r
+
 
 
 class TaskManager(object):