Merge branch 'jk/test-commit-bulk'

A test helper has been introduced to optimize preparation of test
repositories with many simple commits, and a handful of test
scripts have been updated to use it.

* jk/test-commit-bulk:
  t6200: use test_commit_bulk
  t5703: use test_commit_bulk
  t5702: use test_commit_bulk
  t3311: use test_commit_bulk
  t5310: increase the number of bitmapped commits
  test-lib: introduce test_commit_bulk

diff --cc t/test-lib-functions.sh
Simple merge