Skip already migrated rows early (performance improvement)

I checked the reason for the failed test.

Spell-checking found 2 issues:
SourcePluginBase.php:416:36 - Unknown word (sourceid)
SourcePluginBase.php:418:25 - Unknown word (Highwater)

in this part of the code:

      if (!empty($row->getIdMap()['sourceid1'])
        && !$row->needsUpdate()
        && !$this->aboveHighwater($row)
        && !$this->trackChanges) {
        continue;
      }

I have no idea how to fix it. Issues found are not words. One is the array key and the second is the method name.
Do you have any hint of what I can do @cilefen?

I am saving the current patch for reference.

Thanks for reporting.

Issue summary appears to be missing several sections, recommended to use the standard issue template. Will probably need statistics to show the performance improvement

New feature will require test coverage.

All will most likely need a submaintainer approval.

Thanks.

The spelling errors can be skipped by adding the words to core/misc/cspell/dictionary.txt or by using a cspell:ignore line much like core/modules/filter/src/Plugin/migrate/process/FilterID.php does, for example. I am not familiar with current best practices in which one is preferred, but a) core/modules/migrate/tests/src/Kernel/HighWaterTest.php already has a Highwater ignore line b) repeated ignores seemingly are not a problem because there are multiple sourceid ignores in migrate. So: I think you should specifically ignore them instead of editing the dictionary.

Added cspell:ignore, as suggested.

Status remains at NW because patch still needs tests etc