Howto use match (infra) (#1532)

* Howto use match

* Include it in the howto in the index

Minor: emph lines with changes

* Misspelled word

* Typos and suggestions

Co-authored-by: Pierre Equoy <pierre.equoy@canonical.com>

* Re-ordered sections

---------

Co-authored-by: Pierre Equoy <pierre.equoy@canonical.com>

docs/how-to/index.rst

@@ -13,4 +13,5 @@ These how-to guides cover key operations and processes in Checkbox.
    side-loading
    agent-service
    freeze-checkbox-version
-   launcher/*
+   launcher/*
+   using-match

docs/how-to/using-match.rst

@@ -0,0 +1,52 @@
+Using ``match``
+^^^^^^^^^^^^^^^
+
+When a subset of a test plan run fails, it can be expensive to re-run it all.
+To help with this, the ``match`` keyword was introduced. It allows you to
+re-run only a subset of a test plan.
+
+Key features of ``match``:
+
+* All tests in the bootstrap section will always be included
+* Test Selection screen is still shown and functional, but only matching tests are shown
+* Matched tests pull their dependencies automatically
+* ``exclude`` has the priority over ``match``
+
+To only re-run the ``wireless`` portion of the ``sru`` test plan, use the
+following launcher:
+
+.. code-block:: ini
+
+  [test plan]
+  unit = com.canonical.certification::sru
+  forced = yes
+
+  [test selection]
+  match = .*wireless.*
+
+To only re-run the WiFi ``bg_np`` and ``ac_np`` tests for ``wlan0``:
+
+.. code-block:: ini
+  :emphasize-lines: 7-8
+
+  [test plan]
+  unit = com.canonical.certification::sru
+  forced = yes
+
+  [test selection]
+  match =
+    com.canonical.certification::wireless/wireless_connection_open_ac_np_wlan0
+    com.canonical.certification::wireless/wireless_connection_open_bg_np_wlan0
+
+To re-run all wireless tests but ``bg_np``:
+
+.. code-block:: ini
+  :emphasize-lines: 6-7
+
+  [test plan]
+  unit = com.canonical.certification::sru
+  forced = yes
+
+  [test selection]
+  exclude = .*wireless.*bg_np.*
+  match = .*wireless.*