Move the CLI to urfave/cli v3 (closes #110)

Ported per the library's v2-to-v3 migration guide: the app is a root
cli.Command, actions take a context and the command, and flag
environment variables become value sources. -v, -q and the version flag
are local so, as before, only the commands defining them accept them.
Every command stops reading flags at its first argument, as v2 did.
ErrWriter is stdout so usage errors print with their help. The action's
context reaches the manifest download in check, export and list.
testify rises to v1.12.1, which v3 requires; the urfave_cli_no_docs
build tag, which v3 lacks, is dropped. v3 accepts a flag given under two
names, so -v --verbose gives debug output, and the test pinning the
refusal becomes a TestVerboseCount case.

Model: opus-5-5

internal/cli/entry_test.go

@@ -18,7 +18,7 @@ import (
 	"github.com/spf13/afero"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	urfcli "github.com/urfave/cli/v2"
+	urfcli "github.com/urfave/cli/v3"
 	"sneak.berlin/go/mfer/internal/log"
 	"sneak.berlin/go/mfer/mfer"
 )
@@ -264,8 +264,9 @@ func commandsTakingVerbose() [][]string {
 }
 
 // TestVerboseCount asserts that one -v or --verbose gives verbose output and
-// two -v give debug output (issue #125). urfave/cli before v2.25.5 counted a
-// flag given by its alias twice, so one -v gave debug output.
+// two -v, or -v and --verbose, give debug output (issue #125). urfave/cli
+// before v2.25.5 counted a flag given by its alias twice, so one -v gave debug
+// output.
 func TestVerboseCount(t *testing.T) {
 	t.Parallel()
 
@@ -276,6 +277,7 @@ func TestVerboseCount(t *testing.T) {
 		{[]string{"-v"}, log.VerboseLevel},
 		{[]string{testFlagVerbose}, log.VerboseLevel},
 		{[]string{"-v", "-v"}, log.DebugLevel},
+		{[]string{"-v", testFlagVerbose}, log.DebugLevel},
 	}
 
 	for _, command := range commandsTakingVerbose() {
@@ -313,28 +315,6 @@ func TestCombinedShortVerboseRefused(t *testing.T) {
 	}
 }
 
-// TestShortAndLongVerboseRefused asserts that -v and --verbose given together
-// are refused (issue #125): urfave/cli v2 refuses a flag given under two of its
-// names, and one flag with an alias keeps help and parsing simple.
-func TestShortAndLongVerboseRefused(t *testing.T) {
-	t.Parallel()
-
-	for _, command := range commandsTakingVerbose() {
-		args := slices.Concat(command, []string{"-v", testFlagVerbose})
-
-		t.Run(strings.Join(args, " "), func(t *testing.T) {
-			t.Parallel()
-
-			opts := testOpts(args, afero.NewMemMapFs())
-			exitCode, level := runCLIWithLevel(opts)
-
-			assert.Equal(t, 1, exitCode)
-			assert.Contains(t, testStderr(t, opts), "Cannot use two forms of the same flag")
-			assert.Equal(t, log.InfoLevel, level)
-		})
-	}
-}
-
 func TestHelpCommand(t *testing.T) {
 	t.Parallel()
 
@@ -1190,6 +1170,22 @@ func TestGenerateValidatesInputPaths(t *testing.T) {
 	})
 }
 
+// TestFlagAfterArgumentIsArgument asserts that flags are read only before a
+// command's first argument: after it, -v is a path, not the verbose flag.
+func TestFlagAfterArgumentIsArgument(t *testing.T) {
+	t.Parallel()
+
+	fs := afero.NewMemMapFs()
+	require.NoError(t, fs.MkdirAll(testDir, 0o755))
+	writeTestFile(t, fs, testFile1, "content")
+
+	opts := testOpts([]string{testApp, cmdGenerate, testDir, "-v"}, fs)
+	exitCode := runCLI(opts)
+
+	assert.Equal(t, 1, exitCode)
+	assert.Contains(t, testStderr(t, opts), "path does not exist: -v")
+}
+
 func TestCheckDetectsManifestCorruption(t *testing.T) {
 	t.Parallel()