Re: [PATCH v2 7/7] odb/transaction: add transaction interface to write packfiles

> Justin Tobler <jltobler@gmail.com> writes:
> 
> > In git-receive-pack(1), the incoming packfile is written to the ODB via
> > `unpack()`, which spawns git-index-pack(1) or git-unpack-objects(1)
> > directly. With pluggable object databases, an alternative backend may
> > need to handle writing packfile data differently though.
> >
> > Introduce `odb_transaction_write_pack()` as a generic interface to
> > handle writing a packfile to a transaction and use the logic from
> > `unpack()` as the "files" backend implementation. Note that a packfile
> > written via git-index-pack(1) is kept in place by a ".keep" lockfile
> > that must be retained until references are updated. To faciliate this in
> > an ODB backend agnostic manner, the "files" transaction backend takes
> > ownership of these lockfiles and removes them post-commit through its
> > release callback.
> > ...
> > +static int odb_transaction_files_write_pack(struct odb_transaction *base,
> > +					    int pack_fd, struct strbuf *err_msg,
> > +					    const struct odb_transaction_write_pack_opts *opts)
> > +{
> > + ...
> > +		odb_source_prepare(repo->objects->sources,
> > +				   ODB_PREPARE_FLUSH_CACHES);
> > +	}
> 
> This assumes that we are working with the first entry in the
> 'repo->objects->sources' linked list.  Should we not use the source
> actually associated with the current transaction (I am guessing that
> it is 'base->source' but I may be wrong)?