Seems that zif doesn't clean its repo cache when downloading new cache

[elad661]

/var/cache/zif takes around 3.7GB on my system, only 165MB of which are packages.

total 1.1G
1.5M 01cb6b538470f76967c796070101a9af1548cd02ab997f4d4ccc8f40f9e66847-comps-f18.xml
352K 01cb6b538470f76967c796070101a9af1548cd02ab997f4d4ccc8f40f9e66847-comps-f18.xml.gz
137M 05deb912d4538189bae41d0f32e955106c3a3aa62bd9e2161e6b4b97d3f2c483-filelists.sqlite
 24M 05deb912d4538189bae41d0f32e955106c3a3aa62bd9e2161e6b4b97d3f2c483-filelists.sqlite.bz2
137M 0bf20471516ceb2c3af8860e5f504b452e33a6d6bba13e60861bf47a4e389703-filelists.sqlite
 24M 0bf20471516ceb2c3af8860e5f504b452e33a6d6bba13e60861bf47a4e389703-filelists.sqlite.bz2
1.6M 3025ae1f2baea987d71350f9c90e314fa306127790748ffe694e43baa515dac6-comps-f18.xml
396K 3025ae1f2baea987d71350f9c90e314fa306127790748ffe694e43baa515dac6-comps-f18.xml.gz
 73M 3a17beaaf30b845d3131942076c428d9d001f963800db59630a3ee46e360c73e-primary.sqlite
 16M 3a17beaaf30b845d3131942076c428d9d001f963800db59630a3ee46e360c73e-primary.sqlite.bz2
3.8M 3eb22c76fa1fcea6adf8af9e33b028d4b13c11de47c5671654edce880fb9a240-prestodelta.xml
820K 3eb22c76fa1fcea6adf8af9e33b028d4b13c11de47c5671654edce880fb9a240-prestodelta.xml.gz
1.5M 4514c2a04e69240f519666988d7ba3654c209f2ad40e5e80665d4e1482a2a6d8-comps-f18.xml
352K 4514c2a04e69240f519666988d7ba3654c209f2ad40e5e80665d4e1482a2a6d8-comps-f18.xml.gz
 71M 4c212d15ee8ddbfc710e143c6480833f389eee981b37765b50f40e5a916badc0-primary.sqlite
 15M 4c212d15ee8ddbfc710e143c6480833f389eee981b37765b50f40e5a916badc0-primary.sqlite.bz2
748K 548fb9e2cb691fc81e07d292b12d2a85eb55c7537ceb3db0a63b9c340fb72eef-prestodelta.xml
156K 548fb9e2cb691fc81e07d292b12d2a85eb55c7537ceb3db0a63b9c340fb72eef-prestodelta.xml.gz
 72M 54c5ef265733c0278d3ec7fd9da3e81737412672c99b2ba82ca5f22251946ad3-primary.sqlite
 15M 54c5ef265733c0278d3ec7fd9da3e81737412672c99b2ba82ca5f22251946ad3-primary.sqlite.bz2
 73M 5c72fafe9b138d5b1312e85016abd86e1dd13549dfa2baccbd2ec460a64ecd56-primary.sqlite
 45M 5d5177228e4d343e817d05d1a4af830c9082168599e48002d2b04c97337fbfc2-other.sqlite
8.1M 5d5177228e4d343e817d05d1a4af830c9082168599e48002d2b04c97337fbfc2-other.sqlite.bz2
 71M 770d0fe7a4da8ed57c603d00312770b6f9e0da2b926b723daea1112bf4ff8d25-primary.sqlite
 15M 770d0fe7a4da8ed57c603d00312770b6f9e0da2b926b723daea1112bf4ff8d25-primary.sqlite.bz2
 47M a674eb26a5adb742f9f5b95b621bfbf4491e33bf5c2dbcff9e84f456a04ea24f-other.sqlite
8.3M a674eb26a5adb742f9f5b95b621bfbf4491e33bf5c2dbcff9e84f456a04ea24f-other.sqlite.bz2
131M d1a3be041cdc21cfa235d760e221910f9f34014855b84eb2464d0ed1edb6bbeb-filelists.sqlite
 23M d1a3be041cdc21cfa235d760e221910f9f34014855b84eb2464d0ed1edb6bbeb-filelists.sqlite.bz2
3.7M de02d8a9de0c6b7fd74595f35fecc9348652bbb08d662542b31104e1d1e0f8b7-prestodelta.xml
808K de02d8a9de0c6b7fd74595f35fecc9348652bbb08d662542b31104e1d1e0f8b7-prestodelta.xml.gz
 47M e5d2000d57ae2a16d42be4d8cd66a0ab447da31c15e797c93bd07b37aadbbcc5-other.sqlite
8.3M e5d2000d57ae2a16d42be4d8cd66a0ab447da31c15e797c93bd07b37aadbbcc5-other.sqlite.bz2
 16K metalink.xml
4.0K packages
8.0K repomd.xml

After manually running zif clean, /var/cache/zif takes 1.5GB. Still a bit too much. Why do we keep both compressed and decompressed metadata?