Is this possible in any way? I have tried git config --global alias.diff 'diff -b -w' but unfortunately that was not the solution.
Note: Now (after Sept 2014) update gitk config_variables and add ignorespace
https://github.com/git/git/commit/9fabefb1f3f658e77eb18afa3f95efe1a0ee8d0d
All these are flushed to .gitk file.