Change watches

spec.change.watches lets a component opt in to being marked changed when a section of intent.yaml changes, such as environments or groups. Without watches, a change to a global intent section does not re-plan the component.

Watches, their valid values, the --intent-impact flag, and how intent changes combine with file changes and dependencies are documented in change detection.

Note one correction to what this page used to say: a component that merely depends on a changed component is in the change's blast radius, but it is not planned unless the edge is a build input (input: true) or the dependency is include: always. See selection and blast radius.