[sysadmin-bin] Fix git push --mirror invocation

[Bartłomiej Piotrowski <bpiotrowski src gnome org>]

commit 0dc4ca2ecb17883ef90666011ed8274bfc2d5a89
Author: Bartłomiej Piotrowski <bpiotrowski gnome org>
Date:   Mon Oct 28 15:49:08 2019 +0100

    Fix git push --mirror invocation

 git/post-receive-mirror-github | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/git/post-receive-mirror-github b/git/post-receive-mirror-github
index e66a23d..97c50f1 100755
--- a/git/post-receive-mirror-github
+++ b/git/post-receive-mirror-github
@@ -232,7 +232,7 @@ STDERR: {}
         for organization in [gh.organization] + ADDITIONAL_ORGANIZATIONS.get(repo_name, []):
             if refs:
                 try:
-                    command = 'git push --mirror git github com:{}/{} {}:mainline {}'.format(organization, 
github_name)
+                    command = 'git push --mirror git github com:{}/{}'.format(organization, github_name)
                     out = tempfile.NamedTemporaryFile(prefix="github",suffix="std")
                     err = tempfile.NamedTemporaryFile(prefix="github",suffix="err")
                     subprocess.check_call(shlex.split(command), stderr=err, stdout=out)