Add atomic writes, humanized sizes, debug logging, and -v/-q per-command

- Atomic writes for mfer gen: writes to temp file, renames on success,
  cleans up temp on error/interrupt. Prevents empty manifests on Ctrl-C.
- Humanized byte sizes using dustin/go-humanize (e.g., "10 MiB" not "10485760")
- Progress lines clear when done (using ANSI escape \r\033[K])
- Debug logging when files are added to manifest (mfer gen -vv)
- Move -v/-q flags from global to per-command for better UX
- Add tests for atomic write behavior with failing filesystem mock

internal/cli/mfer.go

@@ -57,14 +57,31 @@ func (mfa *CLIApp) VersionString() string {
 	return mfer.Version
 }
 
-func (mfa *CLIApp) setVerbosity(quiet bool, v int) {
+func (mfa *CLIApp) setVerbosity(c *cli.Context) {
 	_, present := os.LookupEnv("MFER_DEBUG")
 	if present {
 		log.EnableDebugLogging()
-	} else if quiet {
+	} else if c.Bool("quiet") {
 		log.SetLevel(log.ErrorLevel)
 	} else {
-		log.SetLevelFromVerbosity(v)
+		log.SetLevelFromVerbosity(c.Count("verbose"))
+	}
+}
+
+// commonFlags returns the flags shared by most commands (-v, -q)
+func commonFlags() []cli.Flag {
+	return []cli.Flag{
+		&cli.BoolFlag{
+			Name:    "verbose",
+			Aliases: []string{"v"},
+			Usage:   "Increase verbosity (-v for verbose, -vv for debug)",
+			Count:   new(int),
+		},
+		&cli.BoolFlag{
+			Name:    "quiet",
+			Aliases: []string{"q"},
+			Usage:   "Suppress output except errors",
+		},
 	}
 }
 
@@ -80,8 +97,6 @@ func (mfa *CLIApp) run(args []string) {
 	log.SetOutput(mfa.Stdout, mfa.Stderr)
 	log.Init()
 
-	var verbosity int
-
 	mfa.app = &cli.App{
 		Name:                 mfa.appname,
 		Usage:                "Manifest generator",
@@ -96,30 +111,17 @@ func (mfa *CLIApp) run(args []string) {
 			mfa.printBanner()
 			return cli.ShowAppHelp(c)
 		},
-		Flags: []cli.Flag{
-			&cli.BoolFlag{
-				Name:    "verbose",
-				Usage:   "Verbosity level",
-				Aliases: []string{"v"},
-				Count:   &verbosity,
-			},
-			&cli.BoolFlag{
-				Name:    "quiet",
-				Usage:   "don't produce output except on error",
-				Aliases: []string{"q"},
-			},
-		},
 		Commands: []*cli.Command{
 			{
 				Name:    "generate",
 				Aliases: []string{"gen"},
 				Usage:   "Generate manifest file",
 				Action: func(c *cli.Context) error {
-					mfa.setVerbosity(c.Bool("quiet"), verbosity)
+					mfa.setVerbosity(c)
 					mfa.printBanner()
 					return mfa.generateManifestOperation(c)
 				},
-				Flags: []cli.Flag{
+				Flags: append(commonFlags(),
 					&cli.BoolFlag{
 						Name:    "FollowSymLinks",
 						Aliases: []string{"follow-symlinks"},
@@ -146,18 +148,18 @@ func (mfa *CLIApp) run(args []string) {
 						Aliases: []string{"P"},
 						Usage:   "Show progress during enumeration and scanning",
 					},
-				},
+				),
 			},
 			{
 				Name:      "check",
 				Usage:     "Validate files using manifest file",
 				ArgsUsage: "[manifest file]",
 				Action: func(c *cli.Context) error {
-					mfa.setVerbosity(c.Bool("quiet"), verbosity)
+					mfa.setVerbosity(c)
 					mfa.printBanner()
 					return mfa.checkManifestOperation(c)
 				},
-				Flags: []cli.Flag{
+				Flags: append(commonFlags(),
 					&cli.StringFlag{
 						Name:    "base",
 						Aliases: []string{"b"},
@@ -173,18 +175,18 @@ func (mfa *CLIApp) run(args []string) {
 						Name:  "no-extra-files",
 						Usage: "Fail if files exist in base directory that are not in manifest",
 					},
-				},
+				),
 			},
 			{
 				Name:      "freshen",
 				Usage:     "Update manifest with changed, new, and removed files",
 				ArgsUsage: "[manifest file]",
 				Action: func(c *cli.Context) error {
-					mfa.setVerbosity(c.Bool("quiet"), verbosity)
+					mfa.setVerbosity(c)
 					mfa.printBanner()
 					return mfa.freshenManifestOperation(c)
 				},
-				Flags: []cli.Flag{
+				Flags: append(commonFlags(),
 					&cli.StringFlag{
 						Name:    "base",
 						Aliases: []string{"b"},
@@ -206,7 +208,7 @@ func (mfa *CLIApp) run(args []string) {
 						Aliases: []string{"P"},
 						Usage:   "Show progress during scanning and hashing",
 					},
-				},
+				),
 			},
 			{
 				Name:  "version",
@@ -240,10 +242,11 @@ func (mfa *CLIApp) run(args []string) {
 				Name:  "fetch",
 				Usage: "fetch manifest and referenced files",
 				Action: func(c *cli.Context) error {
-					mfa.setVerbosity(c.Bool("quiet"), verbosity)
+					mfa.setVerbosity(c)
 					mfa.printBanner()
 					return mfa.fetchManifestOperation(c)
 				},
+				Flags: commonFlags(),
 			},
 		},
 	}