git difftool to give directory compare?

Update June 2012 (2 and an half years later):

This (comparing directories instead of file-by-file) seems to be soon available:
See [ANNOUNCE] Git 1.7.11.rc1:

"git difftool" learned the "--dir-diff" option to spawn external diff tools that can compare two directory hierarchies at a time after populating two temporary directories, instead of running an instance of the external tool once per a file pair.

See "Patch difftool: teach difftool to handle directory diffs"

Original answer (January 2010)

One could pull a copy of the changed files from staging/checked in files into a temp folder, and then open that up. Is that the only option?

Basically yes:

You difftool script would:

• create 2 temp directories
• defines itself as a diff tool
• call git diff
  • which then call itself for file to diff
  • in that mode, the same script, for each files, only copy the two version to diff in the two temp directories
• then go on and call diff tools (like beyondCompare or WinMerge) on the two temp directories

You have one first example in this question.

I always use --dirstat=files:

rudie@devver:virenze$ git diff --dirstat=files
   4.1% modules/custom/virenze_conversations/
   7.0% modules/custom/virenze_crs/
   8.3% modules/custom/

which means I've removed dirs virenze_conversations and virenze_crs in custom. (I don't know what the percentages mean...)

You can probably use all the normal diff options: --cached, branch name etc.