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 marked
local so that, as before, only the commands that define them accept them.
ErrWriter is stdout so usage errors print with their help, as before.
go mod tidy raises testify to v1.12.1, which v3 requires. The
urfave_cli_no_docs build tag is dropped; v3 has no such tag. v3 no longer
refuses a flag given under two of its names, so -v --verbose now gives
debug output, and the test that pinned the refusal becomes a
TestVerboseCount case. Help text follows v3's templates.

Model: opus-5-5

internal/cli/check.go

@@ -16,7 +16,7 @@ import (
 
 	"github.com/dustin/go-humanize"
 	"github.com/spf13/afero"
-	"github.com/urfave/cli/v2"
+	"github.com/urfave/cli/v3"
 	"sneak.berlin/go/mfer/internal/log"
 	"sneak.berlin/go/mfer/mfer"
 )
@@ -208,13 +208,15 @@ func countCheckFailures(
 // findExtraFiles reports files present on disk but absent from the
 // manifest, and anything the search cannot read: each is a failure under
 // --no-extra-files, otherwise a warning.
-func findExtraFiles(ctx *cli.Context, chk *mfer.Checker, failures *int64) error {
+func findExtraFiles(
+	ctx context.Context, cmd *cli.Command, chk *mfer.Checker, failures *int64,
+) error {
 	extraResults := make(chan mfer.Result, 1)
 	extraDone := make(chan struct{})
 
 	go func() {
 		for result := range extraResults {
-			if ctx.Bool("no-extra-files") {
+			if cmd.Bool("no-extra-files") {
 				*failures++
 
 				log.Infof("%s: %s (%s)", result.Status, result.Path, result.Message)
@@ -226,7 +228,7 @@ func findExtraFiles(ctx *cli.Context, chk *mfer.Checker, failures *int64) error
 		close(extraDone)
 	}()
 
-	err := chk.FindExtraFiles(ctx.Context, extraResults)
+	err := chk.FindExtraFiles(ctx, extraResults)
 	if err != nil {
 		return fmt.Errorf("failed to check for extra files: %w", err)
 	}
@@ -238,7 +240,9 @@ func findExtraFiles(ctx *cli.Context, chk *mfer.Checker, failures *int64) error
 
 // runCheck runs the manifest check with progress and result reporting
 // and returns the number of failures.
-func runCheck(ctx *cli.Context, chk *mfer.Checker, showProgress bool) (int64, error) {
+func runCheck(
+	ctx context.Context, cmd *cli.Command, chk *mfer.Checker, showProgress bool,
+) (int64, error) {
 	// Set up results channel
 	results := make(chan mfer.Result, 1)
 
@@ -264,7 +268,7 @@ func runCheck(ctx *cli.Context, chk *mfer.Checker, showProgress bool) (int64, er
 	go countCheckFailures(results, &failures, done)
 
 	// Run check
-	err := chk.Check(ctx.Context, results, progress)
+	err := chk.Check(ctx, results, progress)
 
 	progressWg.Wait()
 
@@ -275,7 +279,7 @@ func runCheck(ctx *cli.Context, chk *mfer.Checker, showProgress bool) (int64, er
 	// Wait for results processing to complete
 	<-done
 
-	err = findExtraFiles(ctx, chk, &failures)
+	err = findExtraFiles(ctx, cmd, chk, &failures)
 	if err != nil {
 		return 0, err
 	}
@@ -283,10 +287,12 @@ func runCheck(ctx *cli.Context, chk *mfer.Checker, showProgress bool) (int64, er
 	return failures, nil
 }
 
-func (mfa *CLIApp) checkManifestOperation(ctx *cli.Context) error {
+func (mfa *CLIApp) checkManifestOperation(
+	ctx context.Context, cmd *cli.Command,
+) error {
 	log.Debug("checkManifestOperation()")
 
-	manifestPath, err := mfa.resolveManifestArg(ctx)
+	manifestPath, err := mfa.resolveManifestArg(cmd)
 	if err != nil {
 		return fmt.Errorf("check: %w", err)
 	}
@@ -303,8 +309,8 @@ func (mfa *CLIApp) checkManifestOperation(ctx *cli.Context) error {
 		manifestPath = tmpPath
 	}
 
-	basePath := ctx.String("base")
-	showProgress := ctx.Bool("progress")
+	basePath := cmd.String("base")
+	showProgress := cmd.Bool("progress")
 
 	log.Infof("checking manifest %s with base %s", manifestPath, basePath)
 
@@ -319,9 +325,9 @@ func (mfa *CLIApp) checkManifestOperation(ctx *cli.Context) error {
 	}
 
 	// Check signature requirement
-	requiredSigner := ctx.String(flagRequireSignature)
+	requiredSigner := cmd.String(flagRequireSignature)
 	if requiredSigner != "" {
-		err = verifyRequiredSigner(ctx.Context, chk, requiredSigner)
+		err = verifyRequiredSigner(ctx, chk, requiredSigner)
 		if err != nil {
 			return err
 		}
@@ -330,7 +336,7 @@ func (mfa *CLIApp) checkManifestOperation(ctx *cli.Context) error {
 	log.Infof("manifest contains %d files, %s", chk.FileCount(),
 		humanize.IBytes(safeUint64(int64(chk.TotalBytes()))))
 
-	failures, err := runCheck(ctx, chk, showProgress)
+	failures, err := runCheck(ctx, cmd, chk, showProgress)
 	if err != nil {
 		return err
 	}