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