Sandbox errors (like missing host tools) are dependent on the host
system and rarely on what is actually done.

It is therefore better to not cache them as they are subject to
change between two runs.

Also add test to ensure sandbox failure are not cached

Reverse the way we were handling caching by only caching
when we know it's a problem with the build or the build is a
success in order not to cache transient errors.

Don't cache sandbox failures

Closes #727

See merge request !895

`bst source-checkout` command was recently added in
!820. Add a
NEWS entry for the new command.

NEWS: Add entry for the new source-checkout command

See merge request !960

richardmaw-codethink authored Nov 14, 2018 and Jürg Billeter committed Nov 19, 2018

The Context was only used to obtain a reference to the CASCache
and set the unused cas_directory field.

The fake context did not set the cache quota, triggering an error. With
CASCache now separate from ArtifactCache, we can instantiate a CASCache
without context.

The default values are in userconfig.yaml, together with the
documentation. The default values should not be duplicated in
_context.py.

_context.py: Drop duplicated default values for user configuration

See merge request !953

Enable this option of 'terminate', which is mentioned in userconfig.yaml
and handled in _frontend/app.py:_handle_failure(). It appears to have
been left out of the valid_actions as an oversight.

Originally introduced in
2622d5da

Use a new helper function to simplify working with nodes that can only
accept certain strings. This will be used when adding the prompt.*
config options.

In later work we can see if this function would be useful elsewhere, and
could be added to '_yaml.py'.

Provide an option in buildstream.conf to disable the 'Would you like to
...' prompt when we cannot resolve a project.

Some users prefer not to be interrupted by such prompts, so pave the way
to creating options to disable all those that might get in the way.

Follow the example of the advice.* options 'git-config', and create a
namespace for these UI options grouped by behaviour, rather than an
over-reaching 'ui.*' namespace. In later work perhaps we'll also add
'advice.*' options.

Add a NEWS item for this.

Provide options in project.conf to disable the 'Are you sure ...'
prompts when making destructive changes:

- Add prompt.really-workspace-close-remove-dir
- Add prompt.really-workspace-reset-hard

Add a NEWS item for these.

Add 'prompt.*' config options to buildstream.conf

See merge request !887

_sandboxremote.py: Add sigterm handler that sends CancelOperation

Closes #725

See merge request !900

This is to be coherent with the rest of the codebase