meta: add `update-yarn` script (#3278)

bin/update-yarn.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+set -o pipefail
+set -o errexit
+set -o nounset
+
+CURRENT_VERSION=$(corepack yarn --version)
+LAST_VERSION=$(curl \
+  -H "Accept: application/vnd.github.v3+json" \
+  https://api.github.com/repos/yarnpkg/berry/releases?per_page=1 | \
+  awk '{ if ($1 == "\"tag_name\":") print $2 }' | \
+  sed 's#^"@yarnpkg/cli/##;s#",$##')
+
+[ "$CURRENT_VERSION" = "$LAST_VERSION" ] && \
+	echo "Already using latest version." && \
+	exit 0
+
+echo "Upgrading to Yarn $LAST_VERSION (from Yarn $CURRENT_VERSION)..."
+
+PLUGINS=$(awk '{ if ($1 == "spec:") print $2 }' .yarnrc.yml)
+
+echo "$PLUGINS" | xargs -n1 -t corepack yarn plugin remove
+
+cp package.json .yarn/cache/tmp.package.json
+sed "s#yarn\": \"$CURRENT_VERSION\"#yarn\": \"$LAST_VERSION\"#;s#\"yarn@$CURRENT_VERSION\"#\"yarn@$LAST_VERSION\"#" .yarn/cache/tmp.package.json > package.json
+rm .yarn/cache/tmp.package.json
+
+echo "$PLUGINS" | xargs -n1 -t corepack yarn plugin import
+corepack yarn
+
+git add package.json yarn.lock
+git add .yarn/plugins