but supports file handlers.
* vc.el (vc-do-command): Use it, instead of call-process.
* net/tramp-vc.el (vc-do-command): Do not advise it if
process-file is fboundp.
* net/tramp.el (tramp-file-name-handler-alist): Add entry for
process-file.
(tramp-handle-process-file): New function.
(tramp-file-name-for-operation): Support process-file.