feat(ci): release notes are generated: the base version, Steamify's changelog section and the commits since the previous release; the mirror's release uses the same text

.github/workflows/iso-1-github-tag.yml

@@ -38,6 +38,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
 
       - name: Tag and release
         env:
@@ -65,17 +67,34 @@ jobs:
           # The ISO's file on the mirror is named after the tag (iso-2-gitea-build.yml, profiledef.sh), so its
           # download link is known now.
           file="steamify-cachyos-${tag#v}-x86_64.iso" dl="$GITEA_URL/$GITEA_REPO/releases/download/$tag"
-          # The Steamify section of CHANGELOG.md ("## CachyOS with Steamify Live ISO"), without its heading.
-          section="$(awk '/^## CachyOS with Steamify Live ISO/ {found = 1; next} found && /^#/ {exit} found' CHANGELOG.md)"
+          # The notes are generated, nothing is written by hand:
+          #  - the CachyOS base version (first line of CHANGELOG.md, the fork's upstream changelog),
+          #  - the Steamify version's own changelog section (steamify-cachyos CHANGELOG.md at the ref or tag it is built from),
+          #  - this repository's commits since the previous release of the same kind.
+          base="$(head -n 1 CHANGELOG.md | sed 's/^# *//')"
+          steamify_notes="$(gh api "repos/theupriser/steamify-cachyos/contents/CHANGELOG.md?ref=${sref:-v$steamify}" -q .content 2> /dev/null | base64 -d 2> /dev/null |
+              awk -v v="$steamify" 'index($0, "## " v " ") == 1 {f = 1; next} f && /^## / {exit} f')"
+          [ "$kind" = release ] && want_pre=false || want_pre=true
+          prev="$(gh release list -L 50 --json tagName,isPrerelease,createdAt -q "[.[] | select(.isPrerelease == $want_pre and .tagName != \"$tag\")] | sort_by(.createdAt) | reverse | .[0].tagName // empty")"
+          if [ -n "$prev" ] && git rev-parse -q --verify "refs/tags/$prev" > /dev/null; then
+            changes="$(git log --no-merges --format='- %s' "$prev..HEAD" | head -n 40)"; since="since $prev"
+          else
+            changes="$(git log --no-merges --format='- %s' -n 15)"; since="(the latest commits: no earlier $kind release)"
+          fi
+          [ -n "$changes" ] || changes="- no changes since $prev"
           notes="![ISO build](https://img.shields.io/badge/ISO_build-running-yellow)
 
-          The ISO is built from \`$(git rev-parse --short HEAD)\` (${{ github.ref_name }}) with Steamify $steamify${sref:+ (branch $sref)} and published on the mirror (GitHub releases take at most 2 GB per file), about half an hour after this release (the mirror's sync, then the build):
+          CachyOS $base with Steamify $steamify${sref:+ (branch $sref)} built in: install CachyOS and turn the PC into a Steam Machine in one go. Built from \`$(git rev-parse --short HEAD)\` (${{ github.ref_name }}) and published on the mirror (GitHub releases take at most 2 GB per file), about 20 minutes after this release:
 
           **Download: [$file]($dl/$file)** ([SHA-256]($dl/$file.sha256), [release page]($GITEA_URL/$GITEA_REPO/releases/tag/$tag))
 
-          Sources: [Steamify](https://github.com/theupriser/steamify-cachyos/tree/${sref:-v$steamify}), this repository at this tag, and the packages' sources at [CachyOS](https://github.com/CachyOS) and [Arch Linux](https://archlinux.org/packages/).
+          ### Steamify $steamify
+          ${steamify_notes:-No changelog section for this version.}
 
-          $section"
+          ### Changes in this ISO $since
+          $changes
+
+          Sources: [Steamify](https://github.com/theupriser/steamify-cachyos/tree/${sref:-v$steamify}), this repository at this tag, and the packages' sources at [CachyOS](https://github.com/CachyOS) and [Arch Linux](https://archlinux.org/packages/)."
           # One ISO per day and kind: the newest build of a day replaces the earlier one (space), here and on the mirror.
           if git ls-remote --exit-code --tags origin "refs/tags/$tag" > /dev/null 2>&1 || gh release view "$tag" > /dev/null 2>&1; then
             echo "$tag exists: replacing it"

.github/workflows/iso-2-gitea-build.yml

@@ -173,15 +173,17 @@ jobs:
           { echo "publish=true"; echo "name=$name"; } >> "$GITHUB_OUTPUT"
           section="$(awk '/^## CachyOS with Steamify Live ISO/ {found = 1; next} found && /^#/ {exit} found' CHANGELOG.md)"
           src="${{ inputs.steamify_ref }}"; src="${src:-v$STEAMIFY_VERSION}"
+          # The same notes as the GitHub release (one source: iso-1 generated them), without its badge line; the
+          # checksum line is added here. Fallback: a short text.
+          if curl -fsS "https://api.github.com/repos/theupriser/steamify-cachyos-live-iso/releases/tags/$tag" -o /tmp/ghrel.json; then
+            jq -r '.body // ""' /tmp/ghrel.json | sed '/ISO build\]/d' > release-notes.md
+          else
+            echo "Built from \`$(git rev-parse --short HEAD)\` ($tag) with Steamify $STEAMIFY_VERSION." > release-notes.md
+          fi
           {
-            echo "Built from \`$(git rev-parse --short HEAD)\` ($tag) with Steamify $STEAMIFY_VERSION."
             echo
             echo "SHA-256: \`$(cut -d' ' -f1 "$iso.sha256")\`, label \`STEAMIFY_${STEAMIFY_VERSION//./_}_$b\`"
-            echo
-            echo "Sources: [Steamify](https://github.com/theupriser/steamify-cachyos/tree/$src), this repository at this tag, and the packages' sources at [CachyOS](https://github.com/CachyOS) and [Arch Linux](https://archlinux.org/packages/)."
-            echo
-            echo "$section"
-          } > release-notes.md
+          } >> release-notes.md
           cat release-notes.md
 
       - name: Publish ${{ github.ref_name }}