Add documentation on workflow_run.workflows

Author: EnricoMi

content/actions/writing-workflows/workflow-syntax-for-github-actions.md

@@ -236,6 +236,10 @@ A boolean specifying whether the secret must be supplied.
 
 {% data reusables.actions.workflows.section-specifying-branches %}
 
+## `on.workflow_run.workflows`
+
+{% data reusables.actions.workflow-run.section-specifying.workflows %}
+
 ## `on.workflow_dispatch`
 
 {% data reusables.actions.workflow-dispatch %}
@@ -1182,7 +1186,7 @@ Allowed expression contexts: `github`, `needs`, and `secrets`.
 
 ## Filter pattern cheat sheet
 
-You can use special characters in path, branch, and tag filters.
+You can use special characters in path, branch, tag, and workflow name filters.
 
 * `*`: Matches zero or more characters, but does not match the `/` character. For example, `Octo*` matches `Octocat`.
 * `**`: Matches zero or more of any character.

data/reusables/actions/workflow-run/section-specifying.workflows.md

@@ -0,0 +1,31 @@
+
+When using the `workflow_run` event, you can specify which workflows can trigger your workflow.
+
+The `workflows` filters accept glob patterns that use characters like `*`, `**`, `+`, `?`, `!` and others to match more than one workflow name. If a name contains any of these characters and you want a literal match, you need to _escape_ each of these special characters with `\`. For more information about glob patterns, see the [AUTOTITLE](/actions/writing-workflows/workflow-syntax-for-github-actions#filter-pattern-cheat-sheet).
+
+For example, a workflow with the following trigger will only run when the workflow named `Build` runs:
+
+```yaml
+on:
+  workflow_run:
+    workflows: ["Build"]
+    types: [requested]
+```
+
+A workflow with the following trigger will only run when a workflow whose name starts with `Build` completed:
+
+```yaml
+on:
+  workflow_run:
+    workflows: ["Build*"]
+    types: [completed]
+```
+
+A workflow with the following trigger will only run when the workflow named `Build C++` completed:
+
+```yaml
+on:
+  workflow_run:
+    workflows: ["Build C\+\+"]
+    types: [completed]
+```