title: How to determine last merged branch in git?
body: <p>I need to determine which was the last branch merged into master.</p>
  
  <p>I have been searching around the git docs but I am still a bit lost. So far I have found the command (assuming master is my current branch)</p>
  
  <pre><code>git log --oneline --graph --decorate
  </code></pre>
  
  <p>Which provides me an output like this</p>
  
  <pre><code>git log --oneline --graph --decorate
  *   12cfc6d (HEAD, origin/master, origin/HEAD, master) Merge branch 'release/VCS_6.12.0-20150826' to master
  |\  
  | *   bef8908 (origin/release/VCS_6.12.0-20150826) Merge remote-tracking branch 'origin/release/VCS_6.12.0-20150826' into release/VCS_6.12.0-20150826
  | |\  
  | | *   c61f97b Merge pull request #12 in COM/vcs from feature/SWAT-47-Loader-JMS to release/VCS_6.12.0-20150826
  | | |\  
  | | | *   33aefe6 (origin/feature/SWAT-47-Loader-JMS) [SWAT-47] Merge from release/VCS_6.12.0-20150826 branch
  | | | |\  
  | | | |/  
  | | |/|   
  | | * | 8f452b0 Revert pom.xml and fix formatting.
  | | * | 128b347 Modified pom.xml by git hook. Command was mvn ci-versions:reset -DforceVersion=feature/VCS-4590_Migrate_translation_util_features
  | | * | eaa9065 VCS-4590 - Migrate dev.vcs translation util to VCS production
  | | | * 6fe1adc [SWAT-47] Move jmsProductUpdateListener bean to publishState-common-meta and properties config to appconfig.
  | | | * ec8311f [SWAT-47] Revert the change of skipping role check for local testing
  | | | * e545332 [SWAT-47] Fix checkstyle issues
  | | | *   0df27b4 Merge remote-tracking branch 'origin/feature/SWAT-47-Loader-JMS' into feature/SWAT-47-Loader-JMS
  | | | |\  
  | | | | * cb87d1b Play with JMS
  | | | * | 5f55b97 [SWAT-47] Added jmsProductUpdateListener to publish JMS message to jmsProductUpdate topic instead of jmsCacheReset topic.
  | | | * | 09f1bc9 [SWAT-47] Play with JMS
  | | | |/  
  </code></pre>
  
  <p>There you can see that the last branch merged was "origin/release/VCS_6.12.0-20150826". </p>
  
  <p>Is there a simpler way to determine this with one (or several) bash commands?</p>