diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 01ec3260..3d692c03 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -9,14 +9,15 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 The format of this change log follows the advice given at [Keep a CHANGELOG](http://keepachangelog.com).
 
 ## [Unreleased]
-
 ### Changed
 - Updated all uses of `actions/checkout` from `v3` (using node 16) to `v4` (using node 20), because [actions using node 16 are deprecated](https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/) and will stop working in the future.
-* ACTION SUGGESTED: In order to avoid the node 16 deprecation warnings, update your workflows to use `actions/checkout@v4`.
+- ACTION SUGGESTED: In order to avoid the node 16 deprecation warnings, update your workflows to use `actions/checkout@v4`.
 
 ### Deprecated
 - The `phpcpd` command (that uses the [PHP Copy/Paste Detector](https://github.com/sebastianbergmann/phpcpd), now abandoned) has been deprecated in this `moodle-plugin-ci` release (4.4.0) and will be removed in 5.0.0. No replacement is planned.
 - ACTION SUGGESTED: In order to avoid deprecation warnings or annotations, proceed to remove this command from your workflows. Note that any use will throw an error in the next major release (5.0.0).
+- The `master` branch of Moodle upstream repositories has been moved to `main` and will stop working soon (see [MDLSITE-7418](https://tracker.moodle.org/browse/MDLSITE-7418) for details). GitHub workflows will start emitting warnings/annotations when uses of the `master` branch are detected.
+- ACTION SUGGESTED: In order to avoid deprecation warnings or annotations, proceed to replace `master` by `main` in your workflows. Note that any use of the former (to be removed) will throw an error in the future.
 
 ## [4.3.2] - 2024-01-26
 ### Changed
diff --git a/src/Command/CopyPasteDetectorCommand.php b/src/Command/CopyPasteDetectorCommand.php
index 634d08fb..3c0efcb9 100644
--- a/src/Command/CopyPasteDetectorCommand.php
+++ b/src/Command/CopyPasteDetectorCommand.php
@@ -38,6 +38,7 @@ protected function configure(): void
 
     protected function execute(InputInterface $input, OutputInterface $output): int
     {
+        // @codeCoverageIgnoreStart
         if (!defined('PHPUNIT_TEST')) { // Only show deprecation warnings in non-test environments.
             trigger_deprecation(
                 'moodle-plugin-ci',
@@ -51,6 +52,7 @@ protected function execute(InputInterface $input, OutputInterface $output): int
                     'is deprecated and will be removed in 5.0.0. No replacement is planned.' . PHP_EOL;
             }
         }
+        // @codeCoverageIgnoreEnd
 
         $timer = new Timer();
         $timer->start();
diff --git a/src/Command/InstallCommand.php b/src/Command/InstallCommand.php
index d086e16e..69c40de2 100644
--- a/src/Command/InstallCommand.php
+++ b/src/Command/InstallCommand.php
@@ -62,6 +62,17 @@ protected function configure(): void
         $extra  = getenv('EXTRA_PLUGINS_DIR') !== false ? getenv('EXTRA_PLUGINS_DIR') : null;
         $node   = getenv('NODE_VERSION') !== false ? getenv('NODE_VERSION') : null;
 
+        // Emit a warning/annotation under GHA if the branch is master (recommending to move to main).
+        // @codeCoverageIgnoreStart
+        if (getenv('GITHUB_ACTIONS')) { // Only show annotations in GitHub Actions.
+            if ($branch === 'master') { // And only if the branch being used is master.
+                echo '::warning title=`master` branch use detected::The `master` branch of Moodle has been ' .
+                    'moved to `main` and will stop working soon. Please consider moving to `main` in your ' .
+                    'workflows. Ref.: MDLSITE-7418' . PHP_EOL;
+            }
+        }
+        // @codeCoverageIgnoreEnd
+
         // As there is not only Travis CI, it can also be passed a generic environment variable.
         if (null === $plugin) {
             $plugin = getenv('CI_BUILD_DIR') !== false ? getenv('CI_BUILD_DIR') : null;