The odb_source API has been refactored to make alternates an
implementation detail of the files backend instead of managing them
at the core object database layer.
* ps/odb-files-alternates:
odb/source: drop `read_alternates` callback
odb/source-files: move alternates into the backend
odb/source-files: extract reading alternates
odb/source: make `will_destroy` an implementation detail
tmp-objdir: replace primary source at creation time
tmp-objdir: manage quarantine as an object directory
tmp-objdir: absorb logic to set and restore primary sources
odb/source-files: add the ability to have multiple object dirs
odb: refactor `odb_find_source()` to yield dirs
odb: refactor `odb_for_each_alternate()` to yield dirs
odb/source-files: introduce `struct odb_files_dir`
commit-graph: stop depending on `struct odb_source`
commit-graph: require resolved packfile paths for `stdin_packs`
Junio C Hamano
1c691e7860