I've attached a patch which adds the desired functionality. The patch is also available here:
https://code.launchpad.net/~sam-lidder/apt/debian-experimental (revision 2250) Notes: - uses the existing --installed flag used by (r)depends - the output for 'Installed Provides' only shows which virtual packages are provided in order to be consistent with the output of 'Provides' in 'apt-cache showpkg <pkg>' - another solution I drafted up was to change the format of 'Installed Provides' to be like that of 'Reverse Depends', so that when '--installed' is passed, the virtual package name is shown along with the installed packages which provide it. This behaviour would be similar to running 'apt-cache showpkg --installed <pkg>' for every package listed under Provides and looking at the 'Installed Reverse Provides' output
155195.patch
Description: Binary data
