doc: drop minimum waiting time as hard guideline

As the [2020 Node.js Contributors Survey][] has shown, the waiting
time for pull requests is a non-trivial obstacle to meaningfully
contributing to Node.js.

To reduce that friction, this PR:

- Drops the 48-hour/7-day waiting times as strict rules.
- Drops the `fast-track` label, which is now the implied default.
- Adds a `wait-for-feedback` label that collaborators can add if they
  think that a pull request *should* remain open for at least 48 hours.
- Reduces the strict requirement for merging something to 1 approval,
  and keep 2 approvals as a strong suggestion.
- Allows immediate reverting of pull requests that have been
  fast-tracked, if deemed necessary.

[2020 Node.js Contributors Survey]: nodejs/TSC#882

Refs: nodejs/TSC#882
Fixes: nodejs#33627

doc/guides/collaborator-guide.md

@@ -11,6 +11,7 @@
   * [Code reviews](#code-reviews)
   * [Consensus seeking](#consensus-seeking)
   * [Waiting for approvals](#waiting-for-approvals)
+  * [Reverting PRs shortly after landing](#reverting-prs-shortly-after-landing)
   * [Testing and CI](#testing-and-ci)
     * [Useful CI jobs](#useful-ci-jobs)
     * [Starting a CI job](#starting-a-ci-job)
@@ -95,9 +96,8 @@ request must pass code review and CI before landing into the codebase.
 
 ### Code reviews
 
-At least two Collaborators must approve a pull request before the pull request
-lands. One Collaborator approval is enough if the pull request has been open
-for more than seven days.
+At least one Collaborator must approve a pull request before the pull request
+lands. Waiting for a second approval is recommended but not mandatory.
 
 Approving a pull request indicates that the Collaborator accepts responsibility
 for the change.
@@ -150,30 +150,28 @@ adding the `tsc-agenda` label to the issue.
 
 ### Waiting for approvals
 
-Before landing pull requests, allow 48 hours for input from other Collaborators.
-Certain types of pull requests can be fast-tracked and can land after a shorter
-delay. For example:
+Before landing pull requests, allow for input from other Collaborators.
+If you expect that a pull request might raise objections,
+wait longer before landing. You can also add the `wait-for-feedback` label
+to pull requests; in that case, it is expected that the pull request will not
+be merged until at least 48 hours after it has been opened, in order to allow
+for everybody to comment on it.
 
-* Focused changes that affect only documentation and/or the test suite:
-  * `code-and-learn` tasks often fall into this category.
-  * `good-first-issue` pull requests might also be suitable.
-* Changes that fix regressions:
-  * Regressions that break the workflow (red CI or broken compilation).
-  * Regressions that happen right before a release, or reported soon after.
+For pull requests that are lacking an approval from a member of the relevant
+team (e.g. @nodejs/http in the case of HTTP changes), it is recommended to keep
+them open for a longer period of time, e.g. several days.
 
-To propose fast-tracking a pull request, apply the `fast-track` label. Then add
-a comment that Collaborators can upvote.
+### Reverting PRs shortly after landing
 
-If someone disagrees with the fast-tracking request, remove the label. Do not
-fast-track the pull request in that case.
+If it has been less than 48 hours after a pull request has been opened and it
+has already been landed, and you object to it in a way that cannot be addressed
+through a new pull request which addresses your concerns, you can open a
+pull request containing a revert and merge it without waiting for approvals or
+CI runs.
 
-The pull request can be fast-tracked if two Collaborators approve the
-fast-tracking request. To land, the pull request itself still needs two
-Collaborator approvals and a passing CI.
-
-Collaborators can request fast-tracking of pull requests they did not author.
-In that case only, the request itself is also one fast-track approval. Upvote
-the comment anyway to avoid any doubt.
+If it has been more than 48 hours since the original pull request was opened,
+you can still open a revert pull request, but should follow the standard rules
+for merging them, i.e. wait for approvals, no objections, and a passing CI run.
 
 ### Testing and CI
 

doc/guides/onboarding-extras.md

@@ -19,6 +19,8 @@ More than one subsystem may be valid for any particular issue or pull request.
 * `discuss`: Things that need larger discussion
 * `feature request`: Any issue that requests a new feature
 * `good first issue`: Issues suitable for newcomers to fix
+* `wait-for-feedback` - Keep this pull request open at least 48 hours before
+  landing, to give others a chance to weigh in.
 * `meta`: Governance, policies, procedures, etc.
 * `tsc-agenda`: Open issues and pull requests with this label will be added to
   the Technical Steering Committee meeting agenda

onboarding.md

@@ -130,10 +130,15 @@ onboarding session.
   reviewers. If you are leaving comments about issues that could be identified
   by tools but are not, consider implementing the necessary tooling.
 * Minimum wait for comments time
-  * There is a minimum waiting time which we try to respect for non-trivial
-    changes so that people who may have important input in such a distributed
-    project are able to respond.
-  * For non-trivial changes, leave the pull request open for at least 48 hours.
+  * Node.js is a distributed project, and it is important that other people
+    have a chance to weigh in on changes that affect them. We do not enforce
+    a fixed waiting time, and pull requests that can generally be expected
+    not to be contentious can be merged as soon as they have approvals and a
+    passing CI run.
+  * If in doubt, leave the pull request open for at least 48 hours.
+  * If you object to a pull request that has already been merged, open a revert
+    PR. If it has been less then 48 hours since the original PR has been opened,
+    you can merge the revert PR immediately.
   * If a pull request is abandoned, check if they'd mind if you took it over
     (especially if it just has nits left).
 * Approving a change
@@ -205,8 +210,7 @@ needs to be pointed out separately during the onboarding.
     -1`
 * Collaborators are in alphabetical order by GitHub username.
 * Optionally, include your personal pronouns.
-* Label your pull request with the `doc`, `notable-change`, and `fast-track`
-  labels.
+* Label your pull request with the `doc`, `notable-change` labels.
 * Run CI on the PR. Use the `node-test-pull-request` CI task.
 * After two Collaborator approvals for the change and two Collaborator approvals
   for fast-tracking, land the PR.