import_all: Run all imports (not just the main datasources' import) with $import_source turned off, so that the Source tables will not be imported a second time when the datasource's main tables are imported. Note that it's not necessary to wait for asynchronous commands after the jobs for the main import are started (so that $import_source is not unset until after they are started), because with_all does not return until all jobs are started and have noted the $import_source setting in effect in the shell environment.