Add the Linux apt/dnf repository to install docs and releases

Documents the signed apt and dnf repository alongside Homebrew and Scoop, and
fires a repository_dispatch on release so the Linux repo rebuilds with the new
packages. The step is skipped when the dispatch token is unset.

.github/workflows/release.yml

@@ -49,6 +49,8 @@ jobs:
       contents: write # create the GitHub release
       packages: write # push the image to ghcr.io
       id-token: write # keyless cosign signing
+    env:
+      LINUX_REPO_DISPATCH_TOKEN: ${{ secrets.LINUX_REPO_DISPATCH_TOKEN }}
     steps:
       - uses: actions/checkout@v7.0.0
         with:
@@ -85,3 +87,15 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           HOMEBREW_TAP_GITHUB_TOKEN: ${{ secrets.HOMEBREW_TAP_GITHUB_TOKEN }}
           SCOOP_BUCKET_GITHUB_TOKEN: ${{ secrets.SCOOP_BUCKET_GITHUB_TOKEN }}
+
+      # Rebuild the Linux apt/dnf repository with the packages just released.
+      # Skipped when the dispatch token is unset, so the release never depends
+      # on it being configured.
+      - name: Refresh the Linux package repository
+        if: env.LINUX_REPO_DISPATCH_TOKEN != ''
+        run: |
+          curl -fsS -X POST \
+            -H "Authorization: Bearer $LINUX_REPO_DISPATCH_TOKEN" \
+            -H "Accept: application/vnd.github+json" \
+            https://api.github.com/repos/tamnd/linux-repo/dispatches \
+            -d '{"event_type":"package-released"}'

README.md

@@ -24,7 +24,7 @@ Full docs and guides live at **[kage.tamnd.com](https://kage.tamnd.com)**.
 go install github.com/tamnd/kage/cmd/kage@latest
 ```
 
-Prefer a prebuilt binary? Grab an archive, a `.deb`/`.rpm`/`.apk`, or a checksum from [releases](https://github.com/tamnd/kage/releases). On a Mac or Windows box, the package managers know it:
+Prefer a prebuilt binary? Grab an archive, a `.deb`/`.rpm`/`.apk`, or a checksum from [releases](https://github.com/tamnd/kage/releases). Or let a package manager handle it:
 
 ```bash
 # Homebrew (macOS)
@@ -33,6 +33,15 @@ brew install tamnd/tap/kage
 # Scoop (Windows)
 scoop bucket add tamnd https://github.com/tamnd/scoop-bucket
 scoop install kage
+
+# apt (Debian, Ubuntu)
+curl -fsSL https://tamnd.github.io/linux-repo/gpg.key | sudo gpg --dearmor -o /usr/share/keyrings/tamnd.gpg
+echo "deb [signed-by=/usr/share/keyrings/tamnd.gpg] https://tamnd.github.io/linux-repo/apt stable main" | sudo tee /etc/apt/sources.list.d/tamnd.list
+sudo apt update && sudo apt install kage
+
+# dnf (Fedora, RHEL)
+sudo dnf config-manager --add-repo https://tamnd.github.io/linux-repo/dnf/tamnd.repo
+sudo dnf install kage
 ```
 
 Or skip installing Chrome yourself and use the container image, which bundles Chromium:

docs/content/getting-started/installation.md

@@ -28,13 +28,31 @@ scoop bucket add tamnd https://github.com/tamnd/scoop-bucket
 scoop install kage
 ```
 
+## Linux (apt and dnf)
+
+A signed apt and dnf repository tracks every release, so `apt upgrade` and
+`dnf upgrade` keep kage current.
+
+```bash
+# Debian, Ubuntu
+curl -fsSL https://tamnd.github.io/linux-repo/gpg.key \
+  | sudo gpg --dearmor -o /usr/share/keyrings/tamnd.gpg
+echo "deb [signed-by=/usr/share/keyrings/tamnd.gpg] https://tamnd.github.io/linux-repo/apt stable main" \
+  | sudo tee /etc/apt/sources.list.d/tamnd.list
+sudo apt update && sudo apt install kage
+
+# Fedora, RHEL
+sudo dnf config-manager --add-repo https://tamnd.github.io/linux-repo/dnf/tamnd.repo
+sudo dnf install kage
+```
+
 ## Release archives and Linux packages
 
 Every [release](https://github.com/tamnd/kage/releases) attaches `tar.gz`
 archives (and a `.zip` for Windows) for Linux, macOS, Windows, and FreeBSD, plus
 `.deb`, `.rpm`, and `.apk` packages and a `checksums.txt` with a cosign
 signature. Download the one for your platform, extract `kage`, and put it on your
-`PATH`.
+`PATH`. To install a package directly without the repo above:
 
 ```bash
 # Debian/Ubuntu