Setting up and using Meld as your git difftool and mergetool on a Mac

Download the latest .dmg package for Mac from here: Meld for OSX

Set meld as your git difftool/mergetool by editing your ~/.gitconfig and adding the following lines, as mentioned in the above link:

[diff]
  tool = meld
[difftool]
  prompt = false
[difftool "meld"]
  trustExitCode = true
  cmd = open -W -a Meld --args \"$LOCAL\" \"$PWD/$REMOTE\"
[merge]
  tool = meld
[mergetool]
  prompt = false
[mergetool "meld"]
  trustExitCode = true
  cmd = open -W -a Meld --args --auto-merge \"$PWD/$LOCAL\" \"$PWD/$BASE\" \"$PWD/$REMOTE\" --output=\"$PWD/$MERGED\"

Use the git difftool command in your repo to compare and edit files between revisions.