The treesum of a filesystem tree is the content hash of all its
files, its directory structure and file metadata.
By storing trees by their treesum we avoid storing duplicates of
identical trees, at the cost of computing the hashes for every
commit to the store.
This has limited benefit as the likelihood of two trees being
identical is slim, in particular when we already have the ability
to cache based on pipeline/stage ID (i.e., we can avoid rebuilding
trees if the pipelines that built them were the same).
Drop the concept of a treesum entirely, even though I very much
liked the idea in theory...
Signed-off-by: Tom Gundersen <teg@jklm.no>
e97f6ef34e