Add script to help draft change log (#296)

* Add script to help draft change log

* updates

Author: trask

.github/scripts/draft-change-log-entries.sh

@@ -0,0 +1,22 @@
+#!/bin/bash -e
+
+version=$(grep -Eo "[0-9]+.[0-9]+.0" version.gradle.kts)
+
+if [[ $version =~ ([0-9]+).([0-9]+).0 ]]; then
+  major="${BASH_REMATCH[1]}"
+  minor="${BASH_REMATCH[2]}"
+else
+  echo "unexpected version: $version"
+  exit 1
+fi
+
+if [[ $minor == 0 ]]; then
+  prior_major=$((major - 1))
+  prior_minor=$(grep -Po "^## Version $prior_major.\K([0-9]+)" CHANGELOG.md | head -1)
+  prior_version="$prior_major.$prior_minor"
+else
+  prior_version="$major.$((minor - 1)).0"
+fi
+
+git log --reverse --pretty=format:"- %s" "v$prior_version"..HEAD \
+  | sed -r 's,\(#([0-9]+)\),\n  ([#\1](https://github.com/open-telemetry/opentelemetry-java-instrumentation/pull/\1)),'

RELEASING.md

@@ -16,6 +16,8 @@ as the last step, which publishes a snapshot build to
 * Merge a pull request to `main` updating the `CHANGELOG.md`.
   * The heading for the release should include the release version but not the release date, e.g.
   `## Version 1.9.0 (unreleased)`.
+  * Use `.github/scripts/draft-change-log-entries.sh` as a starting point for writing the change
+    log.
 * Run the [Prepare release branch workflow](.github/workflows/prepare-release-branch.yml).
 * Review and merge the two pull requests that it creates
   (one is targeted to the release branch and one is targeted to the `main` branch).