add +show-config action to print out the config from the cli

src/cli/show_config.zig

@@ -0,0 +1,46 @@
+const std = @import("std");
+const args = @import("args.zig");
+const Allocator = std.mem.Allocator;
+const Config = @import("../config/Config.zig");
+
+pub const Options = struct {
+    /// If true, print out the default config instead of the user's config.
+    default: bool = false,
+
+    pub fn deinit(self: Options) void {
+        _ = self;
+    }
+};
+
+/// The "show-config" command is used to list all the available configuration
+/// settings for Ghostty.
+///
+/// When executed without any arguments this will list the current settings
+/// loaded by the config file(s). If no config file is found or there aren't
+/// any changes to the settings it will print out the default ones configured
+/// for Ghostty
+///
+/// The "--default" argument will print out all the default settings
+/// configured for Ghostty
+pub fn run(alloc: Allocator) !u8 {
+    var opts: Options = .{};
+    defer opts.deinit();
+
+    {
+        var iter = try std.process.argsWithAllocator(alloc);
+        defer iter.deinit();
+        try args.parse(Options, alloc, &opts, &iter);
+    }
+
+    var config = if (opts.default) try Config.default(alloc) else try Config.load(alloc);
+    defer config.deinit();
+
+    const stdout = std.io.getStdOut().writer();
+
+    const info = @typeInfo(Config);
+    std.debug.assert(info == .Struct);
+
+    try config.formatConfig(stdout);
+
+    return 0;
+}