cylc install

[oliver-sanders]

New command for installing and registering workflows from arbitrary locations into the cylc-run directory.

As per the rose suite-run migration proposal.

Overview Of The New Command

• Check for the existence of a flow.cylc file else fail.
• Configure the run directory as per symlink configuration in globalrc installing the workflow into
  ~/cylc-run/<flow_name>/<run_name> where run_name defaults to run_<n + 1>.
• rsync the directory (applying some pre-defined exclusions) into the run directory.
• Register the workflow.

Out Of Scope

Inexhaustive list of related topics which aren't expected to be resolved as part of this issue:

• Support for recording any cylc play command line arguments for use with future commands.
• Combined actions (e.g. install-play).
• cylc run -> cylc play and related CLI changes.
• Re-installation (cylc reinstall #3890).
• Recording of version control information (install: record version control information #3849).
• Inference of run number by cylc commands when partial registration is provided.
• Support for running other commands against the workflow source (e.g. cylc get-config).

Registration

Registration (or at least much of its functionality) isn't actually going anywhere but we will retire it as a user-facing concept.

Registration (defined in cylc.flow.suite_files.register) currently does the following:

1. Validates workflow name.
2. Validates run directory structure (Disallow nested run directories #3835).
3. Installs workflow definition from specified source.
4. Symlinks flow.cylc -> suite.rc.
5. Creates the .service directory.
6. Creates the .service/source symlink.
7. Allows updating the source with --redirect.

As part of this work the following changes should be made:

• Remove (3) - registration from arbitrary locations no longer supported, use cylc install.
• Remove (6) - source location now specified by cylc install.
• Remove (7) - users can manually update the new _cylc-install/source symlink for now.
• Remove the cylc register command - use cylc install or cylc play for in-place workflows.

Note that that cylc play should still register if not already done as it should still be possible to write a workflow directly in the run directory and run it without using cylc install.