Auto-exclude of cache directories for tar, cpio

[Bryan Ford]

Dear GNU folks,

This message mainly pertains to GNU tar and cpio.  I've written up posted on 
the web a very short proposal, for a convention by which applications that 
create and maintain on-disk caches of any kind with automatically regenerable 
contents would tag those directories in a standard, recognizable fashion.  
These tags could then be used to allow those directories to be automatically 
excluded from backups and the like.  The proposal is here:

        http://www.brynosaurus.com/cachedir/

Although no special improvements are necessarily required to tools like tar 
and cpio to take advantage of such a convention (e.g., the proposal already 
includes one line of shell magic that builds an --exclude-from file 
automatically), but I wanted to contact you anyway in case you have feedback 
on the proposal.  The main venue for public discussion of the proposal is the 
xdg-list on freedesktop.org.

I'd also like to get a sense of whether you might be willing, once the 
proposal solidifies and is supported by more applications, to add a simpler, 
user-friendly option to tar and/or cpio such as "--exclude-caches", which 
would automatically look for cache tags and Do The Right Thing.

Thanks!
Bryan