Move dag's cli method out of DAG.

[potiuk]

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[mik-laj]

I wonder if it would be better to delete it. This was helpful when it was easy available, but that leads to a lot of problems. The basic thing is that we have to support running DAGs that have not been loaded by DagBag, so we have to do many things when import airflow e.g. add new path to sys.path, loading plugins, etc. If we do not prepare the environment while the airflow import is being done, loading the DAG File may fail.

[potiuk]

I wonder if it would be better to delete it. This was helpful when it was easy available, but that leads to a lot of problems. The basic thing is that we have to support running DAGs that have not been loaded by DagBag, so we have to do many things when import airflow e.g. add new path to sys.path, loading plugins, etc. If we do not prepare the environment while the airflow import is being done, loading the DAG File may fail.

Maybe as a next move. For now I want to focus on deps.

[potiuk]

But If you want to remove it - feel free :)

[mik-laj]

We may think about it later. This change now needs an entry in UPDATING.md anyway.

[stale]

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