Add messages for config changes (#3803)

* Automatically label Wasmtime `Config` object changes

* Add the "Label Messager" github action

This allows us to have custom messages left in comments on issues and pull
requests when they get labeled with a specific label.

* Add a message for `wasmtime:config`-labeled pull requests

* CI: Consolidate issue/PR triage workflows

.github/label-messager.json

@@ -0,0 +1,3 @@
+{
+  "wasmtime:config": ".github/label-messager/wasmtime-config.md"
+}

.github/label-messager/wasmtime-config.md

@@ -0,0 +1,51 @@
+It looks like you are changing Wasmtime's configuration options. Make sure to
+complete this check list:
+
+* [ ] If you added a new `Config` method, you wrote extensive documentation for
+      it.
+
+  <details>
+
+  Our documentation should be of the following form:
+
+  ```text
+  Short, simple summary sentence.
+
+  More details. These details can be multiple paragraphs. There should be
+  information about not just the method, but its parameters and results as
+  well.
+
+  Is this method fallible? If so, when can it return an error?
+
+  Can this method panic? If so, when does it panic?
+
+  # Example
+
+  Optional example here.
+  ```
+
+  </details>
+
+* [ ] If you added a new `Config` method, or modified an existing one, you
+  ensured that this configuration is exercised by the fuzz targets.
+
+  <details>
+
+  For example, if you expose a new strategy for allocating the next instance
+  slot inside the pooling allocator, you should ensure that at least one of our
+  fuzz targets exercises that new strategy.
+
+  Often, all that is required of you is to ensure that there is a knob for this
+  configuration option in [`wasmtime_fuzzing::Config`][fuzzing-config] (or one
+  of its nested `struct`s).
+
+  Rarely, this may require authoring a new fuzz target to specifically test this
+  configuration. See [our docs on fuzzing][fuzzing-docs] for more details.
+
+  </details>
+
+* [ ] If you are enabling a configuration option by default, make sure that it
+  has been fuzzed for at least two weeks before turning it on by default.
+
+[fuzzing-config]: https://github.com/bytecodealliance/wasmtime/blob/ca0e8d0a1d8cefc0496dba2f77a670571d8fdcab/crates/fuzzing/src/generators.rs#L182-L194
+[fuzzing-docs]: https://docs.wasmtime.dev/contributing-fuzzing.html

.github/labeler.yml

@@ -66,6 +66,10 @@
 "wasmtime:c-api":
   - "crates/c-api/**"
 
+"wasmtime:config":
+  - "crates/wasmtime/src/config.rs"
+  - "crates/wasmtime/src/config/**"
+
 "wasmtime:docs":
   - "*.md"
   - "docs/**"

.github/workflows/labeler.yml

@@ -1,13 +0,0 @@
-name: "Pull Request Labeler"
-on:
-  schedule:
-    # Run every 5 minutes.
-    - cron: '*/5 * * * *'
-
-jobs:
-  triage:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: bytecodealliance/labeler@schedule-fork
-      with:
-        repo-token: "${{ secrets.GITHUB_TOKEN }}"

.github/workflows/subscribe-to-label.yml

@@ -1,17 +0,0 @@
-name: "Subscribe to Label"
-on:
-  issues:
-    types: ["labeled"]
-  schedule:
-    # Run pull request triage every 5 minutes. Ideally, this would be on
-    # "labeled" types of pull request events, but that doesn't work if the pull
-    # request is from another fork. For example, see
-    # https://github.com/actions/labeler/issues/12
-    - cron: '*/5 * * * *'
-jobs:
-  triage:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: bytecodealliance/subscribe-to-label-action@v1
-      with:
-        repo-token: "${{ secrets.GITHUB_TOKEN }}"

.github/workflows/triage.yml

@@ -0,0 +1,34 @@
+name: "Issue / PR Triage"
+
+on:
+  issues:
+    types: ["labeled"]
+  schedule:
+    # Run pull request triage every 5 minutes. Ideally, this would be on
+    # "labeled" types of pull request events, but that doesn't work if the pull
+    # request is from another fork. For example, see
+    # https://github.com/actions/labeler/issues/12
+    - cron: '*/5 * * * *'
+
+jobs:
+  triage:
+    runs-on: ubuntu-latest
+    steps:
+
+    # Automatically label PRs that touch certain directories with certain
+    # labels.
+    - uses: bytecodealliance/labeler@schedule-fork
+      with:
+        repo-token: "${{ secrets.GITHUB_TOKEN }}"
+      if: ${{ github.event_name == "schedule" }}
+
+    # @-mention people who are subscribed to a label when an issue/PR is given
+    # that label.
+    - uses: bytecodealliance/subscribe-to-label-action@v1
+      with:
+        repo-token: "${{ secrets.GITHUB_TOKEN }}"
+
+    # Leave pre-determined comments on issues/PRs that are given a certain label.
+    - uses: bytecodealliance/label-messager-action@v1
+      with:
+        repo-token: "${{ secrets.GITHUB_TOKEN }}"