doc: trim deprecation level definition text · nodejs/node@6f7de0b

Node.js uses three Deprecation levels:

* *Documentation-Only Deprecation* refers to elements of the Public API that

should be avoided by developers and that might be staged for a runtime

deprecation in a future Node.js major release. An explicit notice indicating

the deprecation status is added to the API documentation but no functional

changes are implemented in the code. By default there will be no deprecation

warnings emitted for such deprecations at runtime. Documentation-only

deprecations may trigger a runtime warning when Node.js is started with the

[`--pending-deprecation`][] flag or the `NODE_PENDING_DEPRECATION=1`

environment variable is set.

* *Runtime Deprecation* refers to the use of process warnings emitted at

runtime the first time that a deprecated API is used. A command-line

switch can be used to escalate such warnings into runtime errors that will

cause the Node.js process to exit. As with Documentation-Only Deprecation,

the documentation for the API must be updated to clearly indicate the

deprecated status.

* *End-of-life* refers to APIs that have gone through Runtime Deprecation and

are no longer subject to the semantic versioning rules used by the project.

* *Documentation-Only Deprecation*: A deprecation notice is added to the API

documentation but no functional changes are implemented in the code. By

default, there will be no warnings emitted for such deprecations at

runtime. Documentation-only deprecations may trigger a runtime warning when

Node.js is started with the [`--pending-deprecation`][] flag or the

`NODE_PENDING_DEPRECATION=1` environment variable is set.

* *Runtime Deprecation*: A warning is emitted at runtime the first time that a

deprecated API is used. The [`--throw-deprecation`][] flag can be used to

escalate such warnings into runtime errors that will cause the Node.js process

to exit. As with Documentation-Only Deprecation, the documentation for the API

must be updated to clearly indicate the deprecated status.

* *End-of-life*: The API is no longer subject to the semantic versioning rules.

Backward-incompatible changes including complete removal of such APIs may

occur at any time.

[TSC]: https://github.com/nodejs/TSC

[_Deprecation_]: https://en.wikipedia.org/wiki/Deprecation

[`--pending-deprecation`]: doc/api/cli.md#--pending-deprecation

[`--throw-deprecation`]: doc/api/cli.md#--throw-deprecation

[`node-core-utils`]: https://github.com/nodejs/node-core-utils

[backporting guide]: doc/guides/backporting-to-release-lines.md

[contributing]: ./doc/guides/contributing/pull-requests.md#commit-message-guidelines