Improve poetry adjustments in CI workflows

[tonyandrewmeyer]

Our workflows that test against charms currently patches in the appropriate version of ops:

      - name: Update 'ops' dependency in test charm to latest
        run: |
          if [ -e "requirements.txt" ]; then
            sed -i -e "/^ops[ ><=]/d" -e "/canonical\/operator/d" -e "/#egg=ops/d" requirements.txt
            echo -e "\ngit+$GITHUB_SERVER_URL/$GITHUB_REPOSITORY@$GITHUB_SHA#egg=ops" >> requirements.txt
          else
            sed -i -e "s/^ops[ ><=].*/ops = {path = \"myops\"}/" pyproject.toml
            poetry lock
          fi

With poetry, this has a side effect that the poetry lock will regenerate the entire lockfile, which could bump dependencies other than ops, which is not the intention for this workflow (but is probably a good idea for the charm itself).

@dimaqq suggested that if we do poetry remove ops and poetry add x that should only make the ops change, which would better match what we want. If that doesn't work, perhaps we can adjust the workflow in some other way to avoid this side effect.

[carlcsaposs-canonical]

I'd suggest using poetry lock --no-update and I think you'll get the behavior you're looking for

(will update lock file for changes in pyproject.toml, but not other changes)

[carlcsaposs-canonical]

you can also use poetry add to update pyproject.toml (no need to run poetry remove)

e.g. poetry add git+https://github.com/canonical/operator/ --lock

[tonyandrewmeyer]

Thanks @carlcsaposs-canonical !