Merge branch 'jk/delta-base-cache'

The delta-base-cache mechanism has been a key to the performance in a repository with a tightly packed packfile, but it did not scale well even with a larger value of core.deltaBaseCacheLimit. * jk/delta-base-cache: t/perf: add basic perf tests for delta base cache delta_base_cache: use hashmap.h delta_base_cache: drop special treatment of blobs delta_base_cache: use list.h for LRU release_delta_base_cache: reuse existing detach function clear_delta_base_cache_entry: use a more descriptive name cache_or_unpack_entry: drop keep_cache parameter