Merge branch 'ps/odb-in-memory' into ps/odb-source-loose

* ps/odb-in-memory: (24 commits)
  t/unit-tests: add tests for the in-memory object source
  odb: generic in-memory source
  odb/source-inmemory: stub out remaining functions
  odb/source-inmemory: implement `freshen_object()` callback
  odb/source-inmemory: implement `count_objects()` callback
  odb/source-inmemory: implement `find_abbrev_len()` callback
  odb/source-inmemory: implement `for_each_object()` callback
  odb/source-inmemory: convert to use oidtree
  oidtree: add ability to store data
  cbtree: allow using arbitrary wrapper structures for nodes
  odb/source-inmemory: implement `write_object_stream()` callback
  odb/source-inmemory: implement `write_object()` callback
  odb/source-inmemory: implement `read_object_stream()` callback
  odb/source-inmemory: implement `read_object_info()` callback
  odb: fix unnecessary call to `find_cached_object()`
  odb/source-inmemory: implement `free()` callback
  odb: introduce "in-memory" source
  odb/transaction: make `write_object_stream()` pluggable
  object-file: generalize packfile writes to use odb_write_stream
  object-file: avoid fd seekback by checking object size upfront
  ...

diff --cc Makefile
Simple merge

diff --cc builtin/unpack-objects.c
Simple merge

diff --cc cache-tree.c
Simple merge

diff --cc meson.build
Simple merge

diff --cc object-file.c
Simple merge

diff --cc odb/streaming.c
Simple merge

diff --cc odb/streaming.h
Simple merge

diff --cc t/meson.build
Simple merge