Some limitations for default simulation environment:
* Verilator's force doesn't update when the RHS changes,
  as documented, so in tests re-force as needed or otherwise
  workaround this limitation.
* Verilator rejects designs that attempt to force an input port,
  with ASSIGNIN.  Force other signals instead.
* `forceInitial` does not appear to work (Verilator?),
  the generated Verilog works in VCS.  Workaround.
  (Chisel `forceInitial` -> `initial force the.lhs.target = rhs_value;`)

* withClock, withReset, and withClockAndReset now have forms that take
  Option[Clock] and Option[Reset]
* Module.clockOption and Module.resetOption return Option[Clock] and
  Option[Reset]

Change the printing of the CIRCT version to show up in the
GITHUB_STEP_SUMMARY.  This makes it easier to know what version CIRCT ran
with, particularly for a nightly run.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Classes can only be elaborated with Definition. Instantiation via D/I is
not yet supported--current instantiation is via an unsafe "by name" API.

This includes the API, Chisel IR, Converter, FIRRTL IR, and Serializer
support for Seqs of Properties (and Property of Seq). This includes
support for values are Seqs of Properties which themselves may or may
not be literals.

This includes support for Property[String] and literals.

This includes the API, Chisel IR, Converter, FIRRTL IR, and Serializer
support for Property literals.

* [dependencies] Fix incorrect Trace test
* [cd] Bump CIRCT from firtool-1.48.0 to firtool-1.50.0

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

This includes the API, Chisel IR, Converter, FIRRTL IR, and Serializer
support for Property connections.

It also includes moving requireVisible from Data to BaseType, which is
required but was omitted from #3442.

Add a CD (continuous delivery) GitHub action that will automatically
create PRs that bump CIRCT to the latest version.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

update ChiselPlugin to name tuples

Remove caching of the `firtool` binary.  Caching empirically provides no
measurable benefit over downloading the binary from a GitHub Release every
time.

This has the effect of avoiding a bug where the "default" old version
would incorrectly hit when the `firtool` version is updated via a change
to the `./etc/circt.json` file.

Additionally, fix another bug where the environment is not populated for
composite actions---the `./etc/circt.json` filename needs to be inlined to
work.  This was previously working because the cache was always hitting.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Change the way that the current CIRCT version is specified.  Previously,
this was code inside a GitHub Action.  Now this is data inside a JSON
file.  This is done to enable other GitHub actions to update the JSON
without having to have permissions to update workflows.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Fix two bugs in nightly CIRCT CI that were causing nightly CI to not
properly run on the correct branch.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

* add aggregate tapping unit tests

* add element accesses of probes to tests

* cleanup dontcares

- Add ability to specify CI branch
- Add CIRCT nightly CI

Add nightly testing using the latest binary of firtool.  This includes
checks that will run for PRs that target the nighlty staging branch,
ci/ci-circt-nightly.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Add the ability to run tests with a specific commit as opposed to always
using the default branch.  This is done to support nightly testing with
CIRCT.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Add a skeleton of a CD GitHub action so that I can play with using
workflow_dispatch to test the real action.  GitHub actions can only be
triggered by workflow_dispatch once the action has been pushed to the
default branch.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Make it such that using "Install CIRCT" does not require specifying a
CIRCT version, instead using the string 'default' as a way to pick the
"default version". The "default version" is the version that Chisel is
tested and released against.

This fixes "Generate Scala CLI Template" which does not care to specify
a CIRCT version.

Change how the CIRCT version is specified for non-nightly flows to a
single environment variable in the ci.yml script.  This makes things
easier for either: (1) a human to update this or (2) a machine to update
this in a CD flow.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Whoopsie...

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Add a skeleton of a CI job for running with CIRCT nightly.  It is
necessary to have an action merged onto the default branch in order to do
manual triggers (workflow_dispatch).  This skeleton is added to facilitate
this.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Change the monolithic test.yml Continuous Integration GitHub Action into a
reusable workflow that is called by a new "ci.yml" workflow.  The
check-tests/all_tests_passed are moved into "ci.yml" as are publishing and
deploy jobs.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

* [ci] Scala-CLI Template Action -> Workflow, NFC

Change the existing Scala-CLI composite action to a workflow.  Update
other workflows which now need to work a little differently.  The main
change is that a reusable workflow can only communicate through
uploads/downloads.  Hence, change the job that publishes the Scala-CLI
template to download this from the new, reusable workflow.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

* [ci] Display Scala-CLI Template in Summary, NFC

Show the resulting Scala-CLI template as a "GITHUB_STEP_SUMMARY" in the
GitHub action for publishing it.  This is likely more useful than making
it available as a download artifact.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

* [ci] Whitespace cleanup, NFC

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

---------

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Add support for grabbing the latest nightly version of `firtool` to the
install-circt action.  This requires passing the "github.token" so that
the GitHub API can be used.  Note that the token is marked as "required",
however, it is only actually needed when using a nightly build.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Firtool improvements have optimized many examples to the point where
they do not show anything. Using registers and assigning the same value
to multiple outputs helps make the examples show interesting naming
behavior.

This option will dump the .fir before invoking firtool.

Additional changes:
* Use os.lib for invoking firtool
* Use lazy serialization to avoid holding the entire FIRRTL in
  memory.
* Mix NoStackTrace into FirtoolNotFound
* Fix detection of no firtool

Also make notice about the older sections bold and thus more noticable.