patch: buffer lines for a same hunk Instead of yielding tokens directly, buffer them if they belong to a same hunk. This makes it easier for the upcoming new worddiff algorithm to only focus on the diff hunk, instead of having to worry about other contents. This breaks how the existing experimental worddiff algorithm works, so the algorithm was removed, and related tests are disabled for now. The next patch will add a new worddiff algorithm. Differential Revision: https://phab.mercurial-scm.org/D3211