transaction: use 'location' instead of 'vfs' in the addbackup method This unlock the backup of file outside of store (eg: bookmarks).

addbackup: handle file in subdirectory The current naming scheme ('journal.backups.<file>') resulted is bad directory name when 'file' was in a subdirectory. We now extract the directory name and create the backupfile within it. We plan to use file in a subdirectory for cachefile.

addbackup: use the vfs for the backup destination too The backup file location was always computed using the opener, bypassing the 'location' setting. (And making the feature broken.)

transaction: set backupentries version to proper value Now that all mechanisms are in place, we can advertise it with a proper new version.

transaction: support cache file in backupentries We do not want to abort if anything wrong happen while handling a cache file. Cache file have way to be invalidated and if old/bad version stay no misbehavior will happen. Proper value will eventually be computed and the wrong will be righten. This changeset use the transaction reporter (usually writing on stderr) to write details about failed cache handling. This will only apply to write operation using a transaction. The usual update during read only operation will stay a debug message. I was on the way to bring these message back to debug level when I realised it could be a feature. People with write access to the repository are likely to have the power to fix error related to cache (and it is valuable to fix them). So let the things as is for now.

transaction: use the location value when doing backup We finally use the 'location' value coupled with the 'vfsmap' to restore backup for the right file.