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)
#header#
# HG changeset patch
# User #author#
# Date #date|date#
# Node ID #node#
#parent%changesetparent#
#desc#
#diff#