o `bst workspace` commands and `bst track` will substitute their
source elements when performing those operations, e.g. performing
`bst track` on a filter element will track the sources on the
element that it depends on (if it has sources).
o Added new simple `make` element
o Switch to Remote Execution CAS-based artifact cache on all platforms.
Artifact servers need to be migrated.
o BuildStream now requires python version >= 3.5
o BuildStream will now automatically clean up old artifacts when it
runs out of space. The exact behavior is configurable in the user's
buildstream.conf.
