[ccache] Cache directory tagging proposal

[Bryan Ford]

Dear ccache folks,

I'm not familiar with ccache (though it looks great!) - but I was pointed to 
it as one application that creates and manages an on-disk cache typically 
located in the user's home directory.  I'd like to inquire if you'd be 
willing to support a trivial convention I'm proposing by which cache-managing 
applications can tag their caches in a standard and recognizable way, so that 
backup and archival software can easily be configured to exclude uselessly 
backing up such regenerable data.  (This would be especially useful with 
ccache, since I understand that ccache caches can be pretty big. :))  All 
that ccache would have to do is write into its cache directory a file named 
".IsCacheDirectory", containing a specific fixed header - probably a 5- or 
10-line change to ccache.  The full (but short) proposal is at:

http://www.brynosaurus.com/cachedir

...and the main discussion of the proposal is occurring on the xdg-list on 
freedesktop.org. The Mozilla folks are already on board and receptive to the 
idea, which is obviously critical since Mozilla caches probably represent the 
bulk of uselessly backed-up cached content on free desktop systems - but I'd 
of course like to get the support of a wider variety of applications. 
Comments and discussion (privately or on the xdg-list) are of course welcome.

Thanks very much!
Bryan