meld-with-3-windows:
launch the meld merge tool with 3 windows

• window 1: diff from BASE to LOCAL
• window 2: diff from BASE to REMOTE
• window 3: three-pane view

Meld is a visual diff and merge tool targeted at developers.

Meld helps you compare files, directories, and projects.

Setup

To use this script, first add this to your gitconfig:

[merge]
  tool = meld-with-3-windows
[mergetool "meld-with-3-windows"]
  cmd = $HOME/bin/gitmerge $BASE $LOCAL $REMOTE $MERGED

See http://blog.wuwon.id.au/2010/09/painless-merge-conflict-resolution-in.html