* specials: comment all parser cases
* specials: scan_graph: early-return if args is null
* specials: fix logic in scan_graph
* tests: add scan_graph parsing test
* specials: separate command parsing from graph parsing
this simplifies the implementation of graph parsing and makes it less ambiguous to parse graphs in contexts where commands are not expected
* specials: tweak comments in scan_graph
* tests: update for scan_command separation
---------
Co-authored-by: bi4k8 <bi4k8@github>
Nested exec expressions like ${execp echo '${execp echo hi}'} are not
evaluated correctly because parsing expressions like these generates and
registers new callbacks but we never wait for these callbacks to
complete before returning the result of the evaluation.
Fix this by re-evaluating expressions after running all pending
callbacks.
- use sccache for build caching
- add coverage reports as build artifacts
- add lcov-summary for coverage summary
- clean up/refactor CI yaml
This resolves the FreeBSD part of #754.
