From DesigningPatterns

Background

meld is graphical diff and merge tool. It has the following advantages over xxdiff:

• Syntax highlighting

It has the following disadvantages compared with xxdiff:

• No documentation.
• No built-in support for integrating the tool with subversion or git. While it does include plugins for a variety of version control systems, these plugins only allow it to be run in stand-alone mode, not to be invoked by the version control systems themselves. Its interface is not well suited to integrating with subversion.
• There is no merge pane when merging files; instead, you merge changes into one of the three inputs (ancestor, your version, or the imported version). This is a big disadvantage.
• It does not seem to merge white-space correctly (white-space seemed to get lost when resolving a difference).

I have found xxdiff to be much closer to a commercial diff and merge tool (say the one shipped with ClearCase) than meld.

Installation

yum install meld

Ensure that the version offered by yum is at least version 1.2, since this was the first version to have any git support.

In order to integrate meld with subversion, customize wrapper scripts as described here. I found it necessary to cat $MINE in the diff3 wrapper, with the assumption that merges were done to "my version" (since there is no proper merge pane).