Publicize behavior of log-view-diff at beginning/end of active region

* lisp/vc/log-view.el (log-view-diff, log-view-diff-changeset):
* doc/emacs/maintaining.texi (VC Change Log): Document behavior of
log-view-diff at the beginning and the end of the log buffer
when the region is active.  (Bug#35624)

* lisp/vc/vc-git.el (vc-git-print-log): Insert newline at the
beginning to enable the feature of diffing with the working revision.
1 job for master in 61 minutes and 41 seconds (queued for 3 seconds)
Status Job ID Name Coverage
failed #1844


Name Stage Failure
test-all Test
Makefile:318: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:293: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:957: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1