Check single file integrity by adding support for cshatag

[jaromil]

This software uses user_xattr to save hashes of files and their mtime, to detect changes.
https://github.com/oriansj/cshatag

It may be used to check both on tomb contents and on tomb files?

[Narrat]

As an optional dep propably not a bad idea. At least for the contents of the tomb itself.
Not sure what to think of it, to check the tomb file itself. If .last could be made bulletproof it would achieve the same? And is a file from the tomb itself

[jaromil]

I think you are right: best save integrity info inside a .integrity file than modify contents of tomb. This can be created and verified running a command on open tombs.