Allow src dir in run dir

[hjoliver]

This is a (very) small change with no associated issue - it just removes a check on source dir location.

Currently cylc install refuses to install a source directory that is located under ~/cylc-run, but I don't think there's a good technical reason for that, is there?? We probably just thought it indicated user CLI error or messy housekeeping practices.

Note there's an additional check that a source dir does not contain _cylc_install and log dirs etc., which should be sufficient for catching the primary CLI error we're presumably trying to catch (i.e. referring to run directory as a source directory).

Unfortunately the location check prevents a sub-worfklow source dir installed as part of a main workflow, from being used as the cylc install source for sub-workflow instances at run time.

Sub-workflow instances can of course be manually installed by simply copying the source from the main workflow run directory each time, but then we don't get the benefits of cylc install and cylc reinstall.

With this check disabled, I have everything I need to get (non-nested) sub-workflows working rather nicely, e.g. with the ability to fix and continue a broken sub-workflow or run a new instance of it by re-triggering the main-workflow task - but I'll demo that next week.

Requirements check-list

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg and conda-environment.yml.
• Does not need tests
• Appropriate change log entry included.
• No documentation update required.

[MetRonnie]

I think a test that you can install from a source dir that is inside ~/cylc-run would be useful.

And perhaps a test that you can't do that if the source dir was itself cylc installed

[hjoliver]

I think a test that you can install from a source dir that is inside ~/cylc-run would be useful.

And perhaps a test that you can't do that if the source dir was itself cylc installed

👍 done

[hjoliver]

@MetRonnie - I'll merge this, as the last item on the rc3 milestone. Perhaps you can do a quick post-merge sanity check on the two unit tests added in response to your comment though.

[MetRonnie]

✔️

[MetRonnie]

[hjoliver]

Hehe, I hope so 🤣

[hjoliver]

[UPDATE] For the record, this superseded the aborted "support for sub-workflows" PRs #4811 #4821. Allowing source dirs under cylc-run allows proper installation of sub-workflows that belong to a parent workflow; beyond that we're leaving it to external scripts to manage sub-workflow names and run directories.