Merge branch 'en/and-cascade-tests' into next

Merge branch 'en/and-cascade-tests' into next

* en/and-cascade-tests: (25 commits)
  t4124 (apply --whitespace): use test_might_fail
  t3404: do not use 'describe' to implement test_cmp_rev
  t3404 (rebase -i): introduce helper to check position of HEAD
  t3404 (rebase -i): move comment to description
  t3404 (rebase -i): unroll test_commit loops
  t3301 (notes): use test_expect_code for clarity
  t1400 (update-ref): use test_must_fail
  t1502 (rev-parse --parseopt): test exit code from "-h"
  t6022 (renaming merge): chain test commands with &&
  test-lib: introduce test_line_count to measure files
  tests: add missing &&, batch 2
  tests: add missing &&
  Introduce sane_unset and use it to ensure proper && chaining
  t7800 (difftool): add missing &&
  t7601 (merge-pull-config): add missing &&
  t7001 (mv): add missing &&
  t6016 (rev-list-graph-simplify-history): add missing &&
  t5602 (clone-remote-exec): add missing &&
  t4026 (color): remove unneeded and unchained command
  t4019 (diff-wserror): add lots of missing &&
  ...

Conflicts:
	t/t6020-merge-df.sh
	t/t6036-recursive-corner-cases.sh
	t/t7006-pager.sh