This commit introduces some changes to how the revng pipeline handles
serializing to disk. Specificaly:
* Pipeline globals (specifically model.yml) are better handled if they
are in a subdirectory. They are now saved in the "context"
subdirectory.
* In python:revng.api the pipeline is serialized whenever there is a
non-reproducible change to the state (e.g. binary upload or model
change).
In the case of analyses this is done conservatively by checking that
the diff produced is not empty.
* The logic for computing a step's subdirectory has been moved to the
pipeline runner, consequently if a step is asked to serialize it
will not create any subdirectories.
* Functionality for saving a single step/context has been exposed in
Pipeline C.
* Finally, all path concatenations are now handled by
llvm::sys::path::append, for extra os-agnosticism.
`revng.api` now autodetects files (libraries, pipeline yamls) for
initialization via the same mechanism used by `revng.cli`. This removes
the need to pass them via environment variables from `revng daemon`
and allows easy interaction with python's C API.
Since PipelineC is not thread-safe, add a lock to all function calls to
it to avoid any thread safety-related issues.
At the same time, use a thread pool to run "expensive" PipelineC
functions in GraphQL (specifically `produce_target` and `run_analysis`)
to avoid problems due to the cooperative nature of Python coroutines.
This commit adds the newly implemented functionality in PipelineC both
in revng.api and the graphql api, allowing:
* retrieval of global variable names
* unwrapping of a single target
* execution of analyses
Giacomo Vercesi