Improve our filter documentation

Closes #278

See merge request !1112

This patch also uncovered the fact that our test_filter_deps_ok() test
has been inaccurate. Thus the element built in this test
(deps-permitted.bst) has been modified so that it build depends on the
input.bst element, as it should.

tests/filter.py: Ensure deps_ok test passes

Fail when we explictly try to include/exclude non-existent domains in a filter element

See merge request !1117

Providing a remote will limit build's pull/push remote actions to
the given remote specifically, ignoring those defined via user or
project configuration.

Add --remote, -r option to bst build, inline with pull & push

See merge request !1119

In order to support use of roaring bitmaps in the loader, we need to
depend on it here.

Signed-off-by: Daniel Silverstone <daniel.silverstone@codethink.co.uk>

The dependency cache in LoadElement causes the peak RAM consumption of
the loader to be exceedingly large, upwards of 25GB for a test of a
Debian stack.  By switching from the old dict cache to a roaring bitmap
based cache, we reduce the cost of the loader cache in RAM terms to
around 5.5GB for the same stack, which makes it plausible for the short
term.

Signed-off-by: Daniel Silverstone <daniel.silverstone@codethink.co.uk>

Switch to roaring bitmaps for the loader dependency caches

See merge request !1128

The unix specification for unix sockets only allocates ~100 characters
for the length of the path. This may be longer than the path for a CI
runner, or the path to a user's buildstream directory.

Add pre-merge tests that use a WSL runner

Closes #852

See merge request !1108

Daniel Silverstone authored Feb 06, 2019 and Benjamin Schubert committed Feb 06, 2019

The licence for roaringbitmap was not compatible.  pyroaring is
a similar project which is MIT licensed and is slightly better on
memory too.

Signed-off-by: Daniel Silverstone <daniel.silverstone@codethink.co.uk>

loadelement.py: Switch from roaringbitmap to pyroaring

Closes #899

See merge request !1133

The 'wallclock-us' is a option that we thought we already had.

Add more log formatting options

See merge request !1125

This commit removes the method ArtifactCache.get_artifact_fullname()
and replaces it with Element.get_artifact_name()

Given a key, we are now able to construct the full name of any of an
element's artifacts.

This object should be used when we want to handle artifact refs directly
from the command line.
An ArtifactElementError has also been added to _exceptions.py

* There is no need for this method to use a cas object.
* Search for artifact globs in the project's element path
* An artifact key is always 64 chars long

A CasBasedDirectory object of an artifacts logs can be obtained
with ArtifactCache.get_artifacts_log(). This ultimately calls
CASCache.get_top_level_dir() to obtain a CasBasedDirectory
of an artifact's subdirectory (or subdirectories).

The loading of elements and the handling of artifacts does not belong
in this module. Such logic should be invoked using the Stream API

This method has been moved to Stream, where is it used there exclusively.

This commit ensures that CASCache.list_refs(), and
ArtifactCache.list_artifacts(), can both handle glob expressions.

_classify_artifacts() no longer filters glob expressions by first
obtaining a list of ALL refs locally cached. We now only obtain refs
specified by the glob expression.

Furthermore, the Project.element_path is used to start searching for
globbed elements as opposed to the Project.directory.

If the artifact ref cannot be split by exactly two forward slashes,
and if the length of the key is not as expected, we should raise
an ArtifactError.