Add support for --help

doc/man/task.1.in

@@ -6,6 +6,8 @@ task \- A command line todo manager.
 .SH SYNOPSIS
 .B task <filter> <command> [ <mods> | <args> ]
 .br
+.B task --help
+.br
 .B task --version
 
 .SH DESCRIPTION
@@ -126,11 +128,15 @@ Taskwarrior. The output and sort behavior of these reports can be configured in
 the configuration file. See also the man page taskrc(5).  There are also other
 read subcommands that are not reports.
 
+.TP
+.B task --help
+Displays the same usage and command documentation as the 'task help' command.
+
 .TP
 .B task --version
-This is the only conventional command line argument that Taskwarrior supports,
-and is intended for add-on scripts to verify the version number of an installed
-Taskwarrior without invoking the mechanisms that create default files.
+This command line argument is intended for add-on scripts to verify the version
+number of an installed Taskwarrior without invoking the mechanisms that create
+default files.
 
 .TP
 .B task <filter>

src/main.cpp

@@ -47,6 +47,11 @@ int main(int argc, const char** argv) {
   Context globalContext;
   Context::setContext(&globalContext);
 
+  // Reuse the existing help command instead of maintaining separate output.
+  if (argc == 2 && !strcmp(argv[1], "--help")) {
+    argv[1] = "help";
+  }
+
   // Lightweight version checking that doesn't require initialization or any I/O.
   if (argc == 2 && !strcmp(argv[1], "--version")) {
     std::cout << VERSION << "\n";

test/commands.test.py

@@ -39,6 +39,15 @@ class TestCommands(TestCase):
     def setUp(self):
         self.t = Task()
 
+    def test_help_option(self):
+        """Verify '--help' is equivalent to the help command"""
+        _, help_out, help_err = self.t("help")
+        _, option_out, option_err = self.t("--help")
+
+        self.assertIn("Usage:", option_out)
+        self.assertEqual(option_out, help_out)
+        self.assertEqual(option_err, help_err)
+
     def test_command_dna(self):
         """Verify 'add', 'modify', 'list' dna"""
         code, out, err = self.t("commands")