title: git rebase already merged branch?
body: <p>I created a feature branch from master branch. After that there is a commit [F1] from feature branch. </p>
  
  <pre><code>        [F1]            -- Feature Branch
         /
  [M1]-[M2]               -- Master Branch
  </code></pre>
  
  <p>After that, feature branch is merged in master branch, and there are two more commits [M3] and [M4] in master branch.    </p>
  
  <pre><code>        [F1]                   -- Feature Branch
         /    \
  [M1]-[M2]-[F1]-[M3]-[M4]       -- Master Branch
  </code></pre>
  
  <p>Now I added two more commits to feature branch.</p>
  
  <pre><code>        [F1]-[F2]-[F3]         -- Feature Branch
         /   \
  [M1]-[M2]-[F1]-[M3]-[M4]       -- Master Branch
  </code></pre>
  
  <p>At this time, should I first rebase the feature branch to master branch, so that feature branch has change of [M3] and [M4] commits, or should I do the git merge directly.</p>
  
  <p>Also, if I do git rebase first, won't the [F1] commit be in both the branches:</p>
  
  <pre><code>                       [F1]-[F2]-[F3]       -- Feature Branch
                         /
  [M1]-[M2]-[F1]-[M3]-[M4]                    -- Master Branch
  </code></pre>