CI: Automatically generate the release changelog (#123)

.github/workflows/build.yml

@@ -598,6 +598,18 @@ jobs:
     if: github.event_name == 'push' && startsWith(github.event.ref, 'refs/tags')
 
     steps:
+      - name: Clone the anvill repository
+        uses: actions/checkout@v2
+        with:
+          path: anvill
+          fetch-depth: 0
+
+      - name: Generate the changelog
+        shell: bash
+        working-directory: anvill
+        run: |
+          ./scripts/generate_changelog.sh changelog.md
+
       - name: Download all artifacts
         uses: actions/download-artifact@v2
 
@@ -611,6 +623,7 @@ jobs:
         with:
           tag_name: ${{ github.ref }}
           release_name: Version ${{ github.ref }}
+          body_path: anvill/changelog.md
           draft: true
           prerelease: true
 

scripts/generate_changelog.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+
+PROJECT_NAME="anvill"
+
+main() {
+  if [[ $# != 1 ]] ; then
+    printf "Usage:\n\tgenerate_changelog.sh <path/to/changelog/file.md>\n"
+    return 1
+  fi
+
+  local output_path="${1}"
+  local current_version="$(git describe --tags --always)"
+  local previous_version="$(git describe --tags --always --abbrev=0 ${current_version}^)"
+
+  echo "Current version: ${current_version}"
+  echo "Previous version: ${previous_version}"
+  echo "Output file: ${output_path}"
+
+  printf "# Changelog\n\n" > "${output_path}"
+  printf "The following are the changes that happened between versions ${previous_version} and ${current_version}\n\n" >> "${output_path}"
+
+  git log ${previous_version}...${current_version} \
+    --pretty=format:" * [%h](http://github.com/lifting-bits/${PROJECT_NAME}/commit/%H) - %s" \
+    --reverse | grep -v 'Merge branch' >> "${output_path}"
+
+  return 0
+}
+
+main $@
+exit $?