Add line counting to DiffCommits

Review Request #6934 — Created Feb. 11, 2015 and submitted — Latest diff uploaded

Information

Review Board
dvcs
a1fa795...

Reviewers

The line counting functionality in the DiffSet model has been
refactored into a mixin. This helper function is now used to calculate
the line counts in the DiffCommit model as well.

Ran unit tests.