Minor fix for revert: No need to make a backup when forgetting added files. echo foo > foo && hg add foo && hg revert foo creates foo.orig, though foo is not changed or deleted.

adding foo
adding bomb
adding a.c
adding dir/a.o
adding dir/b.o
! a.c
! dir/a.o
! dir/b.o
? .hgignore
a.c: unsupported file type (type is fifo)
! a.c