TortoiseSVN

Information on configuring an external diff/merge tool can be found in

http://tortoisesvn.net/docs/release/TortoiseSVN_en/tsvn-dug-settings.html#tsvn-dug-settings-progs

The arguments for comparing two files or two versions of a file should be:

/t1=%bname /t2=%yname %base %mine

With this command line, “original version (%bname)” will be in the left panel and the “modified version (%mine)” will be in the right panel. .  If you want to limit yourself to strictly viewing, rather than editing, the changes, add /ro2 to the beginning of the above command line.

The arugments for merging two versions of a file from a common ancestor should be:

/m /r=%merged /t1=%yname /t2=%bname /t3=%tname /c=%mname %mine %base %theirs

With this command line, “your changes (%mine)” will be in the left panel, the “common ancestor (%base)” will be in the center panel, and “their changes (%theirs)” will be in the right panel.  When you save your merge changes, they will be written to the “merge result (%merged)” file.