Feature request: support backup_exec scripts with context

[roaima]

I've been using backup_exec entries for a while on systems here to drive an rsync script that understands how to copy only files that been modified in the last 3 years.

Unfortunately for my use case, backup_exec scripts are run in $HOME rather than in the snapshot_root, which means I have to pass a load of extra parameters to my script that replicate information already provided to rsnapshot.

I would like to offer a small patch that exports all the simple configuration variables as environment variables ready for such a script to reference. (I considered patching the change directory requirement so that it was specific to the preexec and postexec commands but decided against that because that might break existing scripts.)

Amongst others, the following environment variables are declared for scripts

RSNAPSHOT_cmd_rsync='/usr/bin/rsync'
RSNAPSHOT_cmd_ssh='/usr/bin/ssh'
RSNAPSHOT_rsync_long_args='--delete --delete-excluded --numeric-ids --fake-super --fuzzy --fuzzy --delete-after'
RSNAPSHOT_rsync_short_args='-avzSi'
RSNAPSHOT_snapshot_root='/backup/Rsync/Romania'

rsnapshot.diff.txt

[StefanMoch]

@roaima The patch looks reasonable. Would you mind sending it as pull request or with git format-patch, so that the authorship information is retained?

For integration I would rather see this being configurable to prevent inadvertently leaking information: either on/off switch for the feature or ignore/unignore patterns for the options. I'll have a look into that.

[roaima]

Sure. I'll see if I can work out how to do that.