Issue 3433: Duplicate push accepted by Gerrit
Status:  New
Owner: ----
Reported by org...@gmail.com, Jun 15, 2015
Affected Version: 2.11

What steps will reproduce the problem?
1. Create a commit
2. Create and execute a script that contains:
  git push origin HEAD:refs/for/master &
  git push origin HEAD:refs/for/master &

What is the expected output? What do you see instead?
Only one change should be created. Instead 2 are.