Improve documentation and UI of 'C-x v L'

* lisp/vc/vc.el (vc-print-root-log): Improve the wording of
the doc string and of the prompt for the root directory.

* etc/NEWS: Improve and expand the wording of the changes in
'C-x v L'.

* doc/emacs/maintaining.texi (VC Change Log): Improve and
clarify wording of the 'C-x v L' description.
1 job for master in 90 minutes and 1 second (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #4379
test-all

01:30:01

 
Name Stage Failure
failed
test-all Test The script exceeded the maximum execution time set for the job
  GEN      lisp/eshell/eshell-tests.log
ELC lisp/faces-tests.elc
GEN lisp/faces-tests.log
ELC lisp/ffap-tests.elc
GEN lisp/ffap-tests.log
ELC lisp/filenotify-tests.elc
GEN lisp/filenotify-tests.log
Pulling docker image gitlab/gitlab-runner-helper:x86_64-d0b76032 ...
ERROR: Job failed: execution took longer than 1h30m0s seconds