Add new option --pattern to astCommand to be used by transforms
Add new option --pattern to astCommand to be used by transforms

Summary:
This diff adds a new flag to be used to print the AST structurally. This representation is useful when working with transformations and codemods, to be used in pattern matching.

This new flag is used instead of `--debug` to avoid printing the Locs, as they're just polymorphic in codemods.

Differential Revision: D14113527

fbshipit-source-id: 12f84d2d43de4298a13b3c5973d483f7425fb274

facebook/flow,mroch/flow,samwgoldman/flow,facebook/flow,mroch/flow,gabelevi/flow,facebook/flow,popham/flow,samwgoldman/flow,gabelevi/flow,facebook/flow,facebook/flow,facebook/flow,popham/flow,mroch/flow,samwgoldman/flow,gabelevi/flow,popham/flow,popham/flow,popham/flow,popham/flow,samwgoldman/flow,facebook/flow,gabelevi/flow,popham/flow,gabelevi/flow,samwgoldman/flow,samwgoldman/flow,mroch/flow,samwgoldman/flow,mroch/flow,gabelevi/flow,gabelevi/flow,mroch/flow,mroch/flow