Merge branch 'jk/trace-sifter'

* jk/trace-sifter:
trace: give repo_setup trace its own key
add packet tracing debug code
trace: add trace_strbuf
trace: factor out "do we want to trace" logic
trace: refactor to support multiple env variables
trace: add trace_vprintf

diff --cc builtin/clone.c
Simple merge

diff --cc builtin/fetch.c
Simple merge

diff --cc builtin/push.c
Simple merge

diff --cc builtin/receive-pack.c
Simple merge

diff --cc cache.h
Simple merge