Merge branch 'bc/commit-complete-lines-given-via-m-option' into maint

Merge branch 'bc/commit-complete-lines-given-via-m-option' into maint

'git commit -m "$msg"' used to add an extra newline even when
$msg already ended with one.

* bc/commit-complete-lines-given-via-m-option:
  Documentation/git-commit.txt: rework the --cleanup section
  git-commit: only append a newline to -m mesg if necessary
  t7502: demonstrate breakage with a commit message with trailing newlines
  t/t7502: compare entire commit message with what was expected