Resolving conflicts (in version control)

When Git (or another VCS) attempts to apply a patch that doesn't apply cleanly, it will defer to you, the user, to figure out the right thing to do. Usually you get, dumped in your lap, a file that has all these funny conflict markers in it, showing alternative versions of the content:

    <action name="Execute"><execute>google-chrome</execute></action>
  </keybind>
  <keybind key="W-s-b">
<<<<<<< HEAD
    <action name="Execute"><execute>firefox-3.6</execute></action>
=======
    <action name="Execute"><execute>firefox-3.7</execute></action>
>>>>>>> f50523b...
  </keybind>
  <keybind key="W-a">
    <action name="Execute"><execute>rhythmbox</execute></action>

You can edit that file by hand to get the state you want, but Emacs has a specialized mode for resolving conflicts. Type M‑x vc‑resolve‑conflicts and you get a three-paned frame like the following:

• Press n and p to move between diff hunks.
• For each hunk you can press a or b to transfer the version from the left or right side, respectively, to the output. You can leave the conflicted versions if there's something you really need to fix up by hand.
• Press q when you're done. Emacs returns you to your fixed-up file. Save it.