chore(cfnspec): prepare cfnspec update for autobump (#6557)

* chore(cfnspec): prepare cfnspec update for autobump

`update-cfnspec.sh` is a single script that does the whole bump process
from a fresh repo.

`cfn.version` holds the current version of the CloudFormation version
which changes with the bump process. This is required by delivlib's bump
API here - https://github.com/awslabs/aws-delivlib/blob/0342978b78c5dd2c7bff2279d3b9a43c9e1f359c/lib/bump/bump.ts#L23-L27

* rename to bump

* tweaked per PR feedback

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

packages/@aws-cdk/cfnspec/README.md

@@ -1,8 +1,15 @@
 # AWS CDK CloudFormation Tools
 
-To update the CloudFormation spec to the latest version, run:
+To update the CloudFormation spec, you can run `bump-cfnspec.sh` from a clean repo, as so -
 
-    npm run update
+```
+./scripts/bump-cfnspec.sh
+```
+
+If you wish to only update the CFN spec, make sure to install all dependencies and build the `cfnspec` module,
+and then you can just run:
+
+```
+yarn update
+```
 
-Any JSON hashes are alpha-sorted to make sure that only actual changes appear in
-diffs.

packages/@aws-cdk/cfnspec/build-tools/update.sh

@@ -49,6 +49,10 @@ update-spec \
     spec-source/000_CloudFormationResourceSpecification.json \
     true
 
+echo >&2 "Recording new version..."
+rm -f cfn.version
+node -p "require('${scriptdir}/../spec-source/000_CloudFormationResourceSpecification.json').ResourceSpecificationVersion" > cfn.version
+
 update-spec \
     "Serverless Application Model (SAM) Resource Specification" \
     "https://raw.githubusercontent.com/awslabs/goformation/master/generate/sam-2016-10-31.json" \
@@ -70,7 +74,8 @@ node ${scriptdir}/create-missing-libraries.js || {
 (cd ${scriptdir}/../../../monocdk-experiment && node ./deps.js || true)
 
 # append old changelog after new and replace as the last step because otherwise we will not be idempotent
-cat CHANGELOG.md >> CHANGELOG.md.new
-cp CHANGELOG.md.new CHANGELOG.md
-
-
+_changelog_contents=$(cat CHANGELOG.md.new)
+if [ -n "${_changelog_contents}" ]; then
+    cat CHANGELOG.md >> CHANGELOG.md.new
+    cp CHANGELOG.md.new CHANGELOG.md
+fi

packages/@aws-cdk/cfnspec/cfn.version

@@ -0,0 +1 @@
+11.1.0

scripts/bump-cfnspec.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+set -euo pipefail
+
+if [ ! -f "lerna.json" ]; then
+  echo "This script should be run from the root of the CDK repository"
+  exit 1
+fi
+
+./install.sh
+cd packages/@aws-cdk/cfnspec
+../../../scripts/buildup
+yarn update
+git commit -a -m "feat: cloudformation spec v$(cat cfn.version)" || true # don't fail if there are no updates