Update repos if they exist when populating

bin/populate-repos

@@ -15,6 +15,20 @@ def _clone_repo(target, source):
      ]
     return subprocess.check_output(command)
 
+def _update_repo(target):
+    os.chdir(target)
+    command = ['git', 'checkout', 'master']
+    try:
+        subprocess.check_output(command)
+    except subprocess.CalledProcessError as e:
+        raise Exception("Failed to checkout master for repository at {}: {}".format(target, e))
+
+    command = ['git', 'pull']
+    try:
+        return subprocess.check_output(command)
+    except subprocess.CalledProcessError as e:
+        raise Exception("Failed to update repository at {}: {}".format(target, e))
+
 def _create_virtualenv(target):
     if os.path.exists(os.path.join(target, 've')):
         print("Skipping virtualenv for {}".format(target))
@@ -36,12 +50,15 @@ def main():
     for repo in teamanalysis.repos.REPOSITORIES:
         target = os.path.join(target_root, repo)
         source = 'git@bitbucket.org:Authentise/{}.git'.format(repo)
-        output = _clone_repo(target, source)
-        _create_virtualenv(target)
-        try:
-            _install_dependencies(target)
-        except subprocess.CalledProcessError as e:
-            print("Failed to install dependencies for {}: {}".format(target, e))
+        if not os.path.exists(target):
+            output = _clone_repo(target, source)
+            _create_virtualenv(target)
+            try:
+                _install_dependencies(target)
+            except subprocess.CalledProcessError as e:
+                print("Failed to install dependencies for {}: {}".format(target, e))
+        else:
+            output = _update_repo(target)
 
 if __name__ == '__main__':
     main()