From e97b840ee3a3dd708ce4a51751688e7f3ded295d Mon Sep 17 00:00:00 2001
From: Leandro Rodrigues <leandromqrs@hotmail.com>
Date: Fri, 16 Oct 2026 20:23:43 -0300
Subject: [PATCH] feat(appimage): publish zsync files for delta updates

AppImages had no update information, so AppImageUpdate could not
update them and every update meant downloading the whole bundle.

Embed a gh-releases-zsync update string in the AppImage and have the
build fail when the matching .zsync file is missing. The release
workflows now carry the .zsync files as artifacts, require them for
both architectures, list them in checksums.txt and attach them to the
GitHub release.

The update string matches the versioned AppImage names, so it keeps
working across releases. Releases made before this change cannot be
updated this way.
---
 .github/workflows/release-appimage.yml |  8 ++++++--
 .github/workflows/release.yml          |  4 +++-
 PACKAGING.md                           | 10 ++++++++++
 README.md                              |  4 ++++
 packaging/appimage/build.sh            |  6 +++++-
 5 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/release-appimage.yml b/.github/workflows/release-appimage.yml
index 11c13d5..19aa06d 100644
--- a/.github/workflows/release-appimage.yml
+++ b/.github/workflows/release-appimage.yml
@@ -44,7 +44,9 @@ jobs:
       - uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7
         with:
           name: appimage-x86_64
-          path: dist/*.AppImage
+          path: |
+            dist/*.AppImage
+            dist/*.AppImage.zsync
           if-no-files-found: error
 
   # Fedora container because Arch has no official ARM64 image and Arch Linux ARM lacks
@@ -77,5 +79,7 @@ jobs:
       - uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7
         with:
           name: appimage-aarch64
-          path: dist/*.AppImage
+          path: |
+            dist/*.AppImage
+            dist/*.AppImage.zsync
           if-no-files-found: error
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index be020bf..e83277b 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -173,16 +173,18 @@ jobs:
           for arch in x86_64 aarch64; do
             test -s "dist/zaptide-${GITHUB_REF_NAME}-${arch}.flatpak"
             test -s "dist/zaptide-${GITHUB_REF_NAME}-${arch}.AppImage"
+            test -s "dist/zaptide-${GITHUB_REF_NAME}-${arch}.AppImage.zsync"
             test -s "dist/zaptide-${GITHUB_REF_NAME}-${arch}-linux-gnu.tar.gz"
           done
       - name: Checksums
         working-directory: dist
-        run: sha256sum *.flatpak *.AppImage *.tar.gz > checksums.txt
+        run: sha256sum *.flatpak *.AppImage *.AppImage.zsync *.tar.gz > checksums.txt
       - uses: softprops/action-gh-release@efb35369e0ad2afab669f228072c1b0d510eae64 # v3.0.3
         with:
           files: |
             dist/*.flatpak
             dist/*.AppImage
+            dist/*.AppImage.zsync
             dist/*.tar.gz
             dist/checksums.txt
           fail_on_unmatched_files: true
diff --git a/PACKAGING.md b/PACKAGING.md
index 43ac356..88ee7ae 100644
--- a/PACKAGING.md
+++ b/PACKAGING.md
@@ -68,6 +68,16 @@ and Arch Linux ARM ships libadwaita 1.9. `build.sh` picks the `dnf` path when
 podman run --rm -v "$PWD":/src -w /src -e VERSION=dev registry.fedoraproject.org/fedora:45 ./packaging/appimage/build.sh
 ```
 
+Each AppImage embeds the update information
+`gh-releases-zsync|luminusOS|zaptide|latest|zaptide-*-<arch>.AppImage.zsync`, and
+the build writes the matching `.zsync` file next to it. The release publishes both,
+so [AppImageUpdate](https://github.com/AppImageCommunity/AppImageUpdate) and
+`appimageupdatetool` download only the changed blocks:
+
+```sh
+appimageupdatetool zaptide.AppImage
+```
+
 ## Build dependencies
 
 | Dependency | Fedora | Notes |
diff --git a/README.md b/README.md
index ee05f51..91f9825 100644
--- a/README.md
+++ b/README.md
@@ -80,6 +80,10 @@ chmod +x ./zaptide.AppImage
 ./zaptide.AppImage
 ```
 
+Update an AppImage in place with
+[AppImageUpdate](https://github.com/AppImageCommunity/AppImageUpdate); it
+downloads only what changed.
+
 On first launch, use WhatsApp's **Linked devices** menu to scan the QR code or
 link with your phone number. Recent history may take a few minutes to arrive.
 
diff --git a/packaging/appimage/build.sh b/packaging/appimage/build.sh
index 46f875f..0f02963 100755
--- a/packaging/appimage/build.sh
+++ b/packaging/appimage/build.sh
@@ -2,7 +2,7 @@
 # Builds the ZapTide AppImage with quick-sharun. Run it as root inside an Arch
 # Linux container (Arch ships libadwaita 1.10 and has no 32-bit libs in /usr/lib):
 #   podman run --rm -v "$PWD":/src -w /src archlinux ./packaging/appimage/build.sh
-# The result is dist/zaptide-$ARCH.AppImage.
+# The result is dist/zaptide-$VERSION-$ARCH.AppImage and its .zsync file.
 set -eux
 
 ARCH="$(uname -m)"
@@ -42,6 +42,10 @@ export ICON=data/icons/zaptide.svg
 export DESKTOP=data/dev.luminusos.ZapTide.desktop
 export STARTUPWMCLASS=dev.luminusos.ZapTide
 export GTK_CLASS_FIX=1
+# Delta updates: AppImageUpdate reads this from the AppImage and fetches the
+# .zsync published next to it in the latest GitHub release.
+export UPINFO="gh-releases-zsync|luminusOS|zaptide|latest|zaptide-*-$ARCH.AppImage.zsync"
 
 ./quick-sharun /usr/bin/zaptide
 ./quick-sharun --make-appimage
+test -s "$OUTPATH/$OUTNAME.zsync"