Instead of generic searching you can try a focused search using this forum with simply “crop.” The default search settings is ordered by relevancy, and we have prioritized the documentation above other posts. The fourth search result yields the current best solution:
It is not as simple as a dedicated cropping video tool or a single-clip orientated command line because a video editor is designed to handle multiple clips, possibly at different resolutions and aspect ratios. The notion of cropping an image or video changes its aspect ratio, which conflicts with the notion of a composition aspect ratio.