feat: add Flathub mirror support

README.md

@@ -256,6 +256,7 @@ Using the pre-deployed instance **`xget.xi-xu.me`** or your own deployed instanc
 | openSUSE | `opensuse` | `https://download.opensuse.org/...` | `https://xget.xi-xu.me/opensuse/...` |
 | Arch Linux | `arch` | `https://geo.mirror.pkgbuild.com/...` | `https://xget.xi-xu.me/arch/...` |
 | arXiv | `arxiv` | `https://arxiv.org/...` | `https://xget.xi-xu.me/arxiv/...` |
+| Flathub | `flathub` | `https://dl.flathub.org/...` | `https://xget.xi-xu.me/flathub/...` |
 | F-Droid | `fdroid` | `https://f-droid.org/...` | `https://xget.xi-xu.me/fdroid/...` |
 | Jenkins Plugins | `jenkins` | `https://updates.jenkins.io/...` | `https://xget.xi-xu.me/jenkins/...` |
 | Container Registries | `cr` | See [Container Registries](#container-registries) | See [Container Registries](#container-registries) |
@@ -707,6 +708,22 @@ https://f-droid.org/api/v1/packages/org.fdroid.fdroid
 https://xget.xi-xu.me/fdroid/api/v1/packages/org.fdroid.fdroid
 ```
 
+#### Flathub
+
+```url
+# Flathub repository original URL
+https://dl.flathub.org/repo/summary
+
+# Converted (add flathub prefix)
+https://xget.xi-xu.me/flathub/repo/summary
+
+# Flathub app reference original URL
+https://dl.flathub.org/repo/appstream/org.gnome.gedit.flatpakref
+
+# Converted (add flathub prefix)
+https://xget.xi-xu.me/flathub/repo/appstream/org.gnome.gedit.flatpakref
+```
+
 #### Jenkins Plugins
 
 ```url
@@ -1866,6 +1883,55 @@ task checkFDroidAvailability {
 }
 ```
 
+### Flathub Repository Mirror
+
+#### Configure Flatpak / Flathub to Use Xget Mirror
+
+```bash
+# Add the Flathub remote via the rewritten .flatpakrepo descriptor
+flatpak remote-add --if-not-exists flathub \
+  https://xget.xi-xu.me/flathub/repo/flathub.flatpakrepo
+
+# Or add the OSTree repository directly
+flatpak remote-add --if-not-exists flathub \
+  https://xget.xi-xu.me/flathub/repo/
+```
+
+#### Supported Flathub Services
+
+```url
+# OSTree repository metadata
+https://xget.xi-xu.me/flathub/repo/summary
+https://xget.xi-xu.me/flathub/repo/summary.sig
+
+# Flatpak remote descriptor
+https://xget.xi-xu.me/flathub/repo/flathub.flatpakrepo
+
+# App reference descriptor
+https://xget.xi-xu.me/flathub/repo/appstream/[app-id].flatpakref
+
+# Repository objects and static deltas
+https://xget.xi-xu.me/flathub/repo/objects/...
+https://xget.xi-xu.me/flathub/repo/deltas/...
+```
+
+#### Usage Examples
+
+```bash
+# Inspect remote contents
+flatpak remote-ls flathub
+
+# Install an app from the Xget-backed Flathub mirror
+flatpak install flathub org.gnome.gedit
+
+# Install directly from a rewritten .flatpakref
+flatpak install --from \
+  https://xget.xi-xu.me/flathub/repo/appstream/org.gnome.gedit.flatpakref
+
+# Update installed apps and runtimes
+flatpak update
+```
+
 ### Jenkins Plugin Download
 
 #### Use Xget to Accelerate Jenkins Plugin Download and Update