KDiff3

KDiff3 is a program that

• compares or merges two or three text input files or directories,
• shows the differences line by line and character by character (!),
• provides an automatic merge-facility and
• an integrated editor for comfortable solving of merge-conflicts,
• supports Unicode, UTF-8 and other codecs, autodetection via byte-order-mark "BOM"
• supports KIO on KDE (allows accessing ftp, sftp, fish, smb etc.),
• Printing of differences,
• Manual alignment of lines,
• Automatic merging of version control history ($Log$),
• and has an intuitive graphical user interface.
• Windows-Explorer integration Diff-Ext-for-KDiff3 - shell extension included in installer (originally by Sergey Zorin: see alsoDiff Ext)
• KDE-Konqueror service menu plugin
• Simplified integration with IBM-Rational-Clearcase for Windows (Details).
• Read what else is special in a short abstract (PDF).

kdiff3官网：http://kdiff3.sourceforge.net/