#384: Add | teragrep exec foreachbatch command that sets processing to batch mode

[eemhu]

Adds | teragrep exec foreachbatch command, which turns off batch collect and sets processing to batch mode via step properties.

See issue

• add backing support for | teragrep exec foreachBatch #384

[51-code]

I guess this has to be tested in QA mostly as the unit tests don't support batches of data?

[eemhu]

I guess this has to be tested in QA mostly as the unit tests don't support batches of data?

Yes, with the current testing setup it's not really possible. As-is the test only really tests that the command produces expected results data-wise, and with only one batch.

[51-code]

LGTM now, I don't believe testing batches is possible in unit tests. There's an open issue #134 about that.