Don't abort when backup files already exist. Don't allow alternative names.
Rationale:
- When the user wants to revert, he shouldn't be stopped from doing
this just because some old backups will be overwritten.
- To not clobber important files by accident, alternative names for backup
files were disabled. As the backup target now has a fixed name, the user
doesn't have to be informed about the backup copy (unless --verbose)
# should show copy
copy: foo -> bar
# shouldn't show copy
# should match
rev offset length base linkrev nodeid p1 p2
0 0 5 0 0 2ed2a3912a0b 000000000000 000000000000
renamed from foo:2ed2a3912a0b24502043eae84ee4b279c18b90dd
# should not be renamed
not renamed
# should show copy
copy: foo -> bar
# should show no parents for tip
rev offset length base linkrev nodeid p1 p2
0 0 69 0 1 6ca237634e1f 000000000000 000000000000
1 69 6 1 2 7a1ff8e75f5b 6ca237634e1f 000000000000
2 75 82 1 3 243dfe60f3d9 000000000000 000000000000
# should match
rev offset length base linkrev nodeid p1 p2
0 0 5 0 0 2ed2a3912a0b 000000000000 000000000000
1 5 7 1 2 dd12c926cf16 2ed2a3912a0b 000000000000
renamed from foo:dd12c926cf165e3eb4cf87b084955cb617221c17
# should show no copies