foreach-dataset: move posarg cmd into --cmd?

[yarikoptic]

I would like to continue prior discussion in https://github.com/datalad/datalad/pull/5517#issuecomment-966651403 to get a final decision before we cut a release with new foreach-dataset command.

That would open the possibility to add path as the positional argument, since it

• would be more consistent with the majority of the API where path is used to limit the scope of an operation
• would avoid using the REMAINER ref

cons'ish like

• git submodule foreach takes it as a positional argument
• https://github.com/datalad/datalad/pull/5517#issuecomment-985574268: "with placing command into --cmd (instead of a posarg like run has it) we would bring some "dichotomy" between run and this interfaces." But we agreed that foreach-dataset is not run, so most likely it is ok to have them a bit different

an "alternative" was voiced in https://github.com/datalad/datalad/pull/5517#issuecomment-966651403 -- to add --path kwarg in case we do decide to add path-based limiting. But it still sounds to me suboptimal that would make it inconsistent with the rest of the interfaces.

WDYT?

[adswa]

Given that @yarikoptic said he

would like to continue prior discussion in #5517 (comment) to get a final decision before we cut a release with new foreach-dataset command

I wanted to comment to get this needed discussion going. I don't have any strong opinions, though. I can see some advantages in a dedicated --cmd parameter, if only for making the command call more verbose/readable.

[yarikoptic]

I have no strong opinion given pros cons stated in the description. May be leaning more toward "just let it be positional" due to the pros, and the main motivation for making it --cmd (consistency on having path as the first (or all) positional(s)) being a bit superficial since nobody raised even desire in having path restriction so far.