Merge branch 'group-begin-message' of https://github.com/janslow/task into janslow-group-begin-message

docs/usage.md

@@ -973,6 +973,33 @@ tasks:
  finishes, so you won't have live feedback for commands that take a long time
  to run.
 
+When using the `group` output, you can optionally provide a templated message
+to print at the start of the group. This can be useful for instructing CI
+systems to group all of the output for a given task, such as with [GitHub
+Actions' `::group::` command](https://docs.github.com/en/actions/learn-github-actions/workflow-commands-for-github-actions#grouping-log-lines).
+
+```yaml
+version: '3'
+
+output:
+  group:
+    begin: '::begin::{{.TASK}}'
+    end: '::endgroup::'
+
+tasks:
+  default:
+    cmds:
+      - echo 'Hello, World!'
+    silent: true
+```
+
+```bash
+$ task default
+::begin::default
+Hello, World!
+::endgroup::
+```
+
  The `prefix` output will prefix every line printed by a command with
  `[task-name] ` as the prefix, but you can customize the prefix for a command
  with the `prefix:` attribute: