Make Ghostty release channel aware

Ghostty now has a release channel build configuration. Current valid
values are "tip" and "stable" but I imagine more will be added in the
future.

The release channel is inferred whether the version we specify with the
`-Dversion-string` build flag has a prerelease tag or not. If it does,
the release channel is "tip". If it doesn't, the release channel is
"stable".

This also adds a configuration to specify the release channel for
auto-updates for the macOS application.

.github/workflows/release-tag.yml

@@ -139,7 +139,11 @@ jobs:
       # GhosttyKit is the framework that is built from Zig for our native
       # Mac app to access. Build this in release mode.
       - name: Build GhosttyKit
-        run: nix develop -c zig build -Doptimize=ReleaseFast
+        run: |
+          nix develop -c \
+            zig build \
+            -Doptimize=ReleaseFast \
+            -Dversion-string=${GHOSTTY_VERSION}
 
       # The native app is built with native XCode tooling. This also does
       # codesigning. IMPORTANT: this must NOT run in a Nix environment.

dist/macos/update_appcast_tag.py

@@ -52,8 +52,8 @@ channel = et.find("channel")
 # the same version, Sparkle will report invalid signatures if it picks
 # the wrong one when updating.
 for item in channel.findall("item"):
-    version = item.find("sparkle:version", namespaces)
-    if version is not None and version.text == build:
+    sparkle_version = item.find("sparkle:version", namespaces)
+    if sparkle_version is not None and sparkle_version.text == build:
         channel.remove(item)
 
     # We also remove any item that doesn't have a pubDate. This should

macos/Sources/Features/Update/UpdateDelegate.swift

@@ -3,11 +3,17 @@ import Cocoa
 
 class UpdaterDelegate: NSObject, SPUUpdaterDelegate {
     func feedURLString(for updater: SPUUpdater) -> String? {
-        // Eventually w want to support multiple channels. Sparkle itself supports
-        // channels but we probably don't want some appcasts in the same file (i.e.
-        // tip) so this would be the place to change that. For now, we hardcode the
-        // tip appcast URL since it is all we support.
-        return "https://tip.files.ghostty.org/appcast.xml"
+        guard let appDelegate = NSApplication.shared.delegate as? AppDelegate else {
+            return nil
+        }
+
+        // Sparkle supports a native concept of "channels" but it requires that
+        // you share a single appcast file. We don't want to do that so we
+        // do this instead.
+        switch (appDelegate.ghostty.config.autoUpdateChannel) {
+        case .tip: return "https://tip.files.ghostty.org/appcast.xml"
+        case .stable: return "https://release.files.ghostty.org/appcast.xml"
+        }
     }
 
     func updaterWillRelaunchApplication(_ updater: SPUUpdater) {

macos/Sources/Ghostty/Ghostty.Config.swift

@@ -408,6 +408,17 @@ extension Ghostty {
             return AutoUpdate(rawValue: str) ?? defaultValue
         }
 
+        var autoUpdateChannel: AutoUpdateChannel {
+            let defaultValue = AutoUpdateChannel.stable
+            guard let config = self.config else { return defaultValue }
+            var v: UnsafePointer<Int8>? = nil
+            let key = "auto-update-channel"
+            guard ghostty_config_get(config, &v, key, UInt(key.count)) else { return defaultValue }
+            guard let ptr = v else { return defaultValue }
+            let str = String(cString: ptr)
+            return AutoUpdateChannel(rawValue: str) ?? defaultValue
+        }
+
         var autoSecureInput: Bool {
             guard let config = self.config else { return true }
             var v = false;

macos/Sources/Ghostty/Package.swift

@@ -201,6 +201,11 @@ extension Ghostty {
         case hidden
     }
 
+    /// Enum for auto-update-channel config option
+    enum AutoUpdateChannel: String {
+        case tip
+        case stable
+    }
 }
 
 // MARK: Surface Notification

src/build_config.zig

@@ -58,6 +58,15 @@ pub const BuildConfig = struct {
             "{}",
             .{self.version},
         ));
+        step.addOption(
+            ReleaseChannel,
+            "release_channel",
+            channel: {
+                const pre = self.version.pre orelse break :channel .stable;
+                if (pre.len == 0) break :channel .stable;
+                break :channel .tip;
+            },
+        );
     }
 
     /// Rehydrate our BuildConfig from the comptime options. Note that not all
@@ -82,6 +91,9 @@ pub const BuildConfig = struct {
 pub const version = options.app_version;
 pub const version_string = options.app_version_string;
 
+/// The release channel for this build.
+pub const release_channel = std.meta.stringToEnum(ReleaseChannel, @tagName(options.release_channel)).?;
+
 /// The optimization mode as a string.
 pub const mode_string = mode: {
     const m = @tagName(builtin.mode);
@@ -180,3 +192,12 @@ pub const ExeEntrypoint = enum {
     bench_grapheme_break,
     bench_page_init,
 };
+
+/// The release channel for the build.
+pub const ReleaseChannel = enum {
+    /// Unstable builds on every commit.
+    tip,
+
+    /// Stable tagged releases.
+    stable,
+};

src/cli/version.zig

@@ -25,6 +25,10 @@ pub fn run(alloc: Allocator) !u8 {
     try stdout.print("Ghostty {s}\n\n", .{build_config.version_string});
     if (tty) try stdout.print("\x1b]8;;\x1b\\", .{});
 
+    try stdout.print("Version\n", .{});
+    try stdout.print("  - version: {s}\n", .{build_config.version_string});
+    try stdout.print("  - channel: {s}\n", .{@tagName(build_config.release_channel)});
+
     try stdout.print("Build Config\n", .{});
     try stdout.print("  - Zig version: {s}\n", .{builtin.zig_version_string});
     try stdout.print("  - build mode : {}\n", .{builtin.mode});

src/config/Config.zig

@@ -12,6 +12,7 @@ const Config = @This();
 
 const std = @import("std");
 const builtin = @import("builtin");
+const build_config = @import("../build_config.zig");
 const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
 const ArenaAllocator = std.heap.ArenaAllocator;
@@ -1843,6 +1844,28 @@ term: []const u8 = "xterm-ghostty",
 /// Changing this value at runtime works after a small delay.
 @"auto-update": AutoUpdate = .check,
 
+/// The release channel to use for auto-updates.
+///
+/// The default value of this matches the release channel of the currently
+/// running Ghostty version. If you download a pre-release version of Ghostty
+/// then this will be set to `tip` and you will receive pre-release updates.
+/// If you download a stable version of Ghostty then this will be set to
+/// `stable` and you will receive stable updates.
+///
+/// Valid values are:
+///
+///  * `stable` - Stable, tagged releases such as "1.0.0".
+///  * `tip` - Pre-release versions generated from each commit to the
+///    main branch. This is the version that was in use during private
+///    beta testing by thousands of people. It is generally stable but
+///    will likely have more bugs than the stable channel.
+///
+/// Changing this configuration requires a full restart of
+/// Ghostty to take effect.
+///
+/// This only works on macOS since only macOS has an auto-update feature.
+@"auto-update-channel": ?build_config.ReleaseChannel = null,
+
 /// This is set by the CLI parser for deinit.
 _arena: ?ArenaAllocator = null,
 
@@ -3055,6 +3078,12 @@ pub fn finalize(self: *Config) !void {
             );
         }
     }
+
+    // We can't set this as a struct default because our config is
+    // loaded in environments where a build config isn't available.
+    if (self.@"auto-update-channel" == null) {
+        self.@"auto-update-channel" = build_config.release_channel;
+    }
 }
 
 /// Callback for src/cli/args.zig to allow us to handle special cases