Code clean-up and a fix for "git fetch" by an explicit object name
(as opposed to fetching refs by name).
* jk/fetch-reachability-error-fix:
fetch: do not consider peeled tags as advertised tips
remote.c: make singular free_ref() public
fetch: use free_refs()
pkt-line: prepare buffer before handling ERR packets
upload-pack: send ERR packet for non-tip objects
t5530: check protocol response for "not our ref"
t5516: drop ok=sigpipe from unreachable-want tests