Merge branch '31-diff-collapsing-changed-in-10-6-9' into 'master'

Revert to previous diff pruning behavior

Before 10.6.9, if a rugged diff met the conditions for being too-large
(which obiously meant it was also collapsable), too-large would take
precedence. This reverts the behavior back to that, since gitlab-ce
depends on this

Closes #31

See merge request !132