tree 95f7e68a6d1c1a43a49f1994dee4855c18d05ba9
parent 2875cb45efa98055a859e0b6088150cb1650964a
author Shawn Pearce <spearce@spearce.org> 1502408486 -0700
committer Shawn Pearce <spearce@spearce.org> 1503017255 -0700

dfs: write reftable from DfsGarbageCollector

If a ReftableConfig has been supplied by the caller, write out a
reftable as a sibling of the the GC pack, alongside the heads.

To bootstrap from a non-reftable system, the refs are read from the
DfsRefDatabase if no GC reftables are present.  Its assumed the
references are fully current, and do not need to be merged with any
other reftables.  Any non-GC reftables will be pruned at the end of
the GC cycle, just like any packs that were replaced.

If a GC reftable is present, all existing reftables are compacted, and
references from DfsRefDatabase are only used to seed the packer.  Its
assumed these are consistent with each other.

Change-Id: Ie397eb58aaaefb6865c816d9b39de3ac12998019