[PATCH] gitk: Add checkbutton to ignore space changes

Ignoring space changes can be helpful. For example, a commit claims to only reformat source code and you quickly want to verify if this claim is true. Or a commit accidentally changes code formatting and you want to focus on the real changes. In such cases a button to toggle of whitespace changes would be quite handy. You could quickly toggle between seeing and ignoring whitespace changes. This commit adds such a checkbutton right above the diff view. However, in general it is a good thing to see whitespace changes and therefore the state of the checkbutton is not saved. For example, space changes might happen unintentionally. But they are real changes yielding different sha1s for the blobs involved. Signed-off-by: Steffen Prohaska <prohaska@zib.de> Signed-off-by: Paul Mackerras <paulus@samba.org>