Can't build from subdirectory when using Dockerfile.dazel

[drigz]

If you put a Dockerfile.dazel at the root of your workspace, you can build from the workspace root and everything works nicely. If, however, you cd into a subdirectory and invoke dazel build, dazel will try to pull the default dazel/dazel image instead of using the Dockerfile.dazel.

This appears to be because the workspace path is not joined to the dockerfile variable (source).

It can be worked around by adding the following to .dazelrc at the workspace root:

import dazel
DAZEL_DOCKERFILE = os.path.join(
    dazel.DockerInstance._find_workspace_directory(),
    "Dockerfile.dazel")

But this is obviously fragile.

dazel also appears to create a .dazel_run file in the subdirectory in this case, but this just results in an unnecessary file and and a one-time unnecessary container restart.