In the same spirit as Bug#33084 , the documentation of vc-revert is
1) C-h r
2) m VC Undo
Read this sentence:
Note that ‘C-x v u’ cannot be reversed with the usual undo commands
(see Undo), so use it with care.
To check it is outdated:
1) emacs -Q
2) C-x C-f FILE-UNDER-VERSION-CONTROL
3) Make some changes and then C-x C-s
4) Revert: C-x v u
5) Confirm: yes RET
6) After reverting is done, type C-/
7) Observe that you got your changes back.