Read a path or URL named help or h as an argument (closes #198)

On gen, check, freshen, fetch, list and export, a first argument of
`help` or `h` ran urfave/cli's built-in help command, so
`check help --require-signature FPR` printed help and passed. Those
commands now set urfave/cli's HideHelpCommand, which leaves out their
help command; the root keeps its own, so `mfer help` and
`mfer help check` still work. `check DIR --help` failed with
`No help topic for 'DIR'`; their CommandNotFound now prints the
command's own help, as `check --help` does.

Model: opus-5-5

internal/cli/entry_test.go

@@ -36,6 +36,8 @@ const (
 	testFlagNoExtra = "--no-extra-files"
 	testFlagVersion = "--version"
 	testFlagVerbose = "--verbose"
+	testFlagHelp    = "--help"
+	testCmdHelp     = "help"
 )
 
 var errSimulatedWrite = errors.New("simulated write failure")
@@ -321,7 +323,7 @@ func TestHelpCommand(t *testing.T) {
 	t.Parallel()
 
 	fs := afero.NewMemMapFs()
-	opts := testOpts([]string{testApp, "--help"}, fs)
+	opts := testOpts([]string{testApp, testFlagHelp}, fs)
 
 	exitCode := runCLI(opts)
 
@@ -1807,6 +1809,82 @@ func TestGenerateReadsPathAfterDoubleDash(t *testing.T) {
 	assert.Equal(t, testFileTxt, files[0].GetPath())
 }
 
+// TestPathNamedHelp runs gen, then check with --require-signature, on a
+// directory named help and on one named h, the two names of urfave/cli's
+// help command. gen must write the manifest into the directory, and check
+// must refuse it as unsigned.
+//
+//nolint:paralleltest // changes the process-global working directory
+func TestPathNamedHelp(t *testing.T) {
+	for _, name := range []string{testCmdHelp, "h"} {
+		t.Run(name, func(t *testing.T) {
+			chdirTemp(t)
+
+			fs := afero.NewOsFs()
+			require.NoError(t, fs.Mkdir(name, 0o755))
+			writeTestFile(t, fs, filepath.Join(name, testFileTxt), "content")
+
+			opts := testOpts([]string{testApp, cmdGenerate, "-q", name}, fs)
+			require.Equal(t, 0, runCLI(opts), testStderr(t, opts))
+
+			files := manifestFiles(t, fs, filepath.Join(name, defaultManifestName))
+			require.Len(t, files, 1)
+
+			opts = testOpts([]string{
+				testApp, cmdCheck, "-q", name, "--" + flagRequireSignature, msgFpA,
+			}, fs)
+			assert.Equal(t, 1, runCLI(opts))
+			assert.Contains(t, testStderr(t, opts), "manifest is not signed")
+		})
+	}
+}
+
+// TestCommandsReadHelpAsArgument runs each command that takes a path or URL
+// on help and on h where nothing by that name exists. Each must fail on the
+// missing path or bad URL instead of printing its help.
+func TestCommandsReadHelpAsArgument(t *testing.T) {
+	t.Parallel()
+
+	for _, command := range []string{
+		cmdGenerate, cmdCheck, cmdFreshen, cmdList, cmdExport, cmdFetch,
+	} {
+		for _, name := range []string{testCmdHelp, "h"} {
+			t.Run(command+" "+name, func(t *testing.T) {
+				t.Parallel()
+
+				opts := testOpts([]string{testApp, command, name}, afero.NewMemMapFs())
+				assert.Equal(t, 1, runCLI(opts))
+				assert.NotContains(t, testStdout(t, opts), "USAGE:")
+			})
+		}
+	}
+}
+
+// TestCheckHelpBesideArgument runs check with --help or -h before and after
+// a directory, and runs help check. Each must print what check --help prints.
+func TestCheckHelpBesideArgument(t *testing.T) {
+	t.Parallel()
+
+	want := testOpts([]string{testApp, cmdCheck, testFlagHelp}, afero.NewMemMapFs())
+	require.Equal(t, 0, runCLI(want))
+	require.Contains(t, testStdout(t, want), "Validate files using manifest file")
+
+	for _, args := range [][]string{
+		{cmdCheck, testDir, testFlagHelp},
+		{cmdCheck, testFlagHelp, testDir},
+		{cmdCheck, testDir, "-h"},
+		{testCmdHelp, cmdCheck},
+	} {
+		t.Run(strings.Join(args, " "), func(t *testing.T) {
+			t.Parallel()
+
+			opts := testOpts(slices.Concat([]string{testApp}, args), afero.NewMemMapFs())
+			assert.Equal(t, 0, runCLI(opts), testStderr(t, opts))
+			assert.Equal(t, testStdout(t, want), testStdout(t, opts))
+		})
+	}
+}
+
 func TestCheckDetectsManifestCorruption(t *testing.T) {
 	t.Parallel()
 

internal/cli/mfer.go

@@ -168,6 +168,17 @@ func refuseExtraArgs(_ context.Context, cmd *cli.Command) error {
 	return nil
 }
 
+// showCommandHelp is the CommandNotFound of the commands that take a path or
+// URL. Those commands set HideHelpCommand, so that a path or URL named help or
+// h is an argument rather than urfave/cli's help command; each sets it itself,
+// because on the root it would also remove `mfer help`. With --help,
+// urfave/cli looks the command's first argument up as a help topic, so
+// `check DIR --help` asks for a topic DIR and finds none; this prints the
+// command's own help instead, as `check --help` does.
+func showCommandHelp(ctx context.Context, cmd *cli.Command, _ string) {
+	_ = cli.ShowCommandHelp(ctx, cmd.Root(), cmd.Name)
+}
+
 // requireSignatureFlag returns the --require-signature flag taken by the
 // check and fetch subcommands.
 func requireSignatureFlag() *cli.StringFlag {
@@ -191,10 +202,12 @@ func includePermissionsFlag() *cli.BoolFlag {
 
 func (mfa *CLIApp) generateCommand() *cli.Command {
 	return &cli.Command{
-		Name:      cmdGenerate,
-		Aliases:   []string{"gen"},
-		Usage:     "Generate manifest file",
-		ArgsUsage: "[path ...]",
+		Name:            cmdGenerate,
+		Aliases:         []string{"gen"},
+		Usage:           "Generate manifest file",
+		ArgsUsage:       "[path ...]",
+		HideHelpCommand: true,
+		CommandNotFound: showCommandHelp,
 		Action: func(ctx context.Context, cmd *cli.Command) error {
 			mfa.setVerbosity(cmd)
 			mfa.printBanner()
@@ -253,10 +266,12 @@ func (mfa *CLIApp) generateCommand() *cli.Command {
 
 func (mfa *CLIApp) checkCommand() *cli.Command {
 	return &cli.Command{
-		Name:         cmdCheck,
-		Usage:        "Validate files using manifest file",
-		ArgsUsage:    manifestArgsUsage,
-		ArgValidator: refuseExtraArgs,
+		Name:            cmdCheck,
+		Usage:           "Validate files using manifest file",
+		ArgsUsage:       manifestArgsUsage,
+		ArgValidator:    refuseExtraArgs,
+		HideHelpCommand: true,
+		CommandNotFound: showCommandHelp,
 		Action: func(ctx context.Context, cmd *cli.Command) error {
 			mfa.setVerbosity(cmd)
 			mfa.printBanner()
@@ -287,10 +302,12 @@ func (mfa *CLIApp) checkCommand() *cli.Command {
 
 func (mfa *CLIApp) freshenCommand() *cli.Command {
 	return &cli.Command{
-		Name:         cmdFreshen,
-		Usage:        "Update manifest with changed, new, and removed files",
-		ArgsUsage:    manifestArgsUsage,
-		ArgValidator: refuseExtraArgs,
+		Name:            cmdFreshen,
+		Usage:           "Update manifest with changed, new, and removed files",
+		ArgsUsage:       manifestArgsUsage,
+		ArgValidator:    refuseExtraArgs,
+		HideHelpCommand: true,
+		CommandNotFound: showCommandHelp,
 		Action: func(ctx context.Context, cmd *cli.Command) error {
 			mfa.setVerbosity(cmd)
 			mfa.printBanner()
@@ -338,10 +355,12 @@ func (mfa *CLIApp) freshenCommand() *cli.Command {
 
 func (mfa *CLIApp) exportCommand() *cli.Command {
 	return &cli.Command{
-		Name:         cmdExport,
-		Usage:        "Export manifest contents as JSON",
-		ArgsUsage:    "[manifest file or URL]",
-		ArgValidator: refuseExtraArgs,
+		Name:            cmdExport,
+		Usage:           "Export manifest contents as JSON",
+		ArgsUsage:       "[manifest file or URL]",
+		ArgValidator:    refuseExtraArgs,
+		HideHelpCommand: true,
+		CommandNotFound: showCommandHelp,
 		Action: func(ctx context.Context, cmd *cli.Command) error {
 			mfa.setVerbosity(cmd)
 
@@ -364,12 +383,14 @@ func (mfa *CLIApp) versionCommand() *cli.Command {
 
 func (mfa *CLIApp) listCommand() *cli.Command {
 	return &cli.Command{
-		Name:         cmdList,
-		Aliases:      []string{"ls"},
-		Usage:        "List files in manifest",
-		ArgsUsage:    manifestArgsUsage,
-		ArgValidator: refuseExtraArgs,
-		Action:       mfa.listManifestOperation,
+		Name:            cmdList,
+		Aliases:         []string{"ls"},
+		Usage:           "List files in manifest",
+		ArgsUsage:       manifestArgsUsage,
+		ArgValidator:    refuseExtraArgs,
+		HideHelpCommand: true,
+		CommandNotFound: showCommandHelp,
+		Action:          mfa.listManifestOperation,
 		Flags: []cli.Flag{
 			&cli.BoolFlag{
 				Name:    "long",
@@ -386,10 +407,12 @@ func (mfa *CLIApp) listCommand() *cli.Command {
 
 func (mfa *CLIApp) fetchCommand() *cli.Command {
 	return &cli.Command{
-		Name:         cmdFetch,
-		Usage:        "fetch manifest and referenced files",
-		ArgsUsage:    "URL",
-		ArgValidator: refuseExtraArgs,
+		Name:            cmdFetch,
+		Usage:           "fetch manifest and referenced files",
+		ArgsUsage:       "URL",
+		ArgValidator:    refuseExtraArgs,
+		HideHelpCommand: true,
+		CommandNotFound: showCommandHelp,
 		Action: func(ctx context.Context, cmd *cli.Command) error {
 			mfa.setVerbosity(cmd)
 			mfa.printBanner()