Modify size of context shown

[cweiske]

Sometimes it is helpful to show more than one or two lines of context around a diff.

There should be an option to set the context size in number of lines.

[relaxnow]

+1

[sun]

I agree. Normally, the default diff context is 3 lines.

Briefly looked into this already, but apparently, the number of diff context lines is not a static value, but determined automagically based on the "longest lines in common", involving some highly complex math.