Releasing 2.0.0-alpha.4 (#5279)

* Version bump

* Split generate_changelog.sh into separate script

Can be run in the format `generate_changelog.sh $previous_version $version`.

* remove early exit from publish_draft_release.sh

* adding changelog

* ci: change last_github_release to also find pre-releases

Co-authored-by: Martin Pugh <pugh@s3kr.it>

substrate/.maintain/gitlab/generate_changelog.sh

@@ -0,0 +1,73 @@
+#!/usr/bin/env bash
+
+# shellcheck source=lib.sh
+source "$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )/lib.sh"
+
+version="$2"
+last_version="$1"
+
+all_changes="$(sanitised_git_logs "$last_version" "$version")"
+runtime_changes=""
+api_changes=""
+client_changes=""
+changes=""
+
+while IFS= read -r line; do
+  pr_id=$(echo "$line" | sed -E 's/.*#([0-9]+)\)$/\1/')
+
+  # Skip if the PR has the silent label - this allows us to skip a few requests
+  if has_label 'paritytech/substrate' "$pr_id" 'B0-silent'; then
+    continue
+  fi
+  if has_label 'paritytech/substrate' "$pr_id" 'B1-runtimenoteworthy'; then
+    runtime_changes="$runtime_changes
+$line"
+  fi
+  if has_label 'paritytech/substrate' "$pr_id" 'B1-clientnoteworthy'; then
+    client_changes="$client_changes
+$line"
+  fi
+   if has_label 'paritytech/substrate' "$pr_id" 'B1-apinoteworthy' ; then
+    api_changes="$api_changes
+$line"
+    continue
+  fi
+done <<< "$all_changes"
+
+# Make the substrate section if there are any substrate changes
+if [ -n "$runtime_changes" ] ||
+   [ -n "$api_changes" ] ||
+   [ -n "$client_changes" ]; then
+  changes=$(cat << EOF
+Substrate changes
+-----------------
+
+EOF
+)
+  if [ -n "$runtime_changes" ]; then
+    changes="$changes
+
+Runtime
+-------
+$runtime_changes"
+  fi
+  if [ -n "$client_changes" ]; then
+    changes="$changes
+
+Client
+------
+$client_changes"
+  fi
+  if [ -n "$api_changes" ]; then
+    changes="$changes
+
+API
+---
+$api_changes"
+  fi
+  release_text="$release_text
+
+$changes"
+fi
+
+echo "$changes"