config: command-arg to specify arguments to the executed command

Fixes #744

src/config/Config.zig

@@ -268,6 +268,16 @@ palette: Palette = .{},
 ///
 command: ?[]const u8 = null,
 
+/// A single argument to pass to the command. This can be repeated to
+/// pass multiple arguments. This slightly clunky configuration style is
+/// so that Ghostty doesn't have to perform any sort of shell parsing
+/// to find argument boundaries.
+///
+/// This cannot be used to override argv[0]. argv[0] will always be
+/// set by Ghostty to be the command (possibly with a hyphen-prefix to
+/// indicate that it is a login shell, depending on the OS).
+@"command-arg": RepeatableString = .{},
+
 /// The directory to change to after starting the command.
 ///
 /// The default is "inherit" except in special scenarios listed next.

src/termio/Exec.zig

@@ -744,24 +744,25 @@ const Subprocess = struct {
             env.remove("GHOSTTY_MAC_APP");
         }
 
-        // If we're NOT in a flatpak (usually!), then we just exec the
+        // Build our args list
-        // process directly. If we are in a flatpak, we use flatpak-spawn
+        const args = args: {
-        // to escape the sandbox.
+            const cap = 1 + opts.full_config.@"command-arg".list.items.len;
-        const args = if (!internal_os.isFlatpak()) try alloc.dupe(
+            var args = try std.ArrayList([]const u8).initCapacity(alloc, cap);
-            []const u8,
-            &[_][]const u8{argv0_override orelse path},
-        ) else args: {
-            var args = try std.ArrayList([]const u8).initCapacity(alloc, 8);
             defer args.deinit();
 
-            // We run our shell wrapped in a /bin/sh login shell because
+            if (!internal_os.isFlatpak()) {
-            // some systems do not properly initialize the env vars unless
+                try args.append(argv0_override orelse path);
-            // we start this way (NixOS!)
+            } else {
-            try args.append("/bin/sh");
+                // We run our shell wrapped in a /bin/sh login shell because
-            try args.append("-l");
+                // some systems do not properly initialize the env vars unless
-            try args.append("-c");
+                // we start this way (NixOS!)
-            try args.append(path);
+                try args.append("/bin/sh");
+                try args.append("-l");
+                try args.append("-c");
+                try args.append(path);
+            }
 
+            try args.appendSlice(opts.full_config.@"command-arg".list.items);
             break :args try args.toOwnedSlice();
         };