Merge branch 'bp/diff-no-index-strbuf-fix' into maint

The directory path used in "git diff --no-index", when it recurses
down, was broken with a recent update after v1.7.10.1 release.

By Bobby Powers
* bp/diff-no-index-strbuf-fix:
  diff --no-index: don't leak buffers in queue_diff
  diff --no-index: reset temporary buffer lengths on directory iteration