Make code lint-clean under the canonical golangci-lint config

150 findings fixed: linter autofixes for whitespace style (wsl_v5,
nlreturn, noinlineerr), named returns removed, magic numbers replaced
with named constants, static errNotRegular error, explicit Close/Parse
error handling, unused cobra params renamed to _, and runReport/
runTrees/hashPass split into helpers to satisfy cyclop, gocognit, and
funlen. Behavior verified unchanged against the README smoke test.

progress.go

@@ -12,12 +12,23 @@ import (
 // is not a TTY.
 const plainInterval = 5 * time.Second
 
+// barThrottle caps how often the TTY progress bar redraws.
+const barThrottle = 100 * time.Millisecond
+
+// walkSpinnerType selects the progressbar library's spinner style used
+// for the walk pass, which has no known total.
+const walkSpinnerType = 14
+
+// percentScale converts a fraction to a percentage.
+const percentScale = 100
+
 // stderrIsTTY reports whether stderr is attached to a terminal.
 func stderrIsTTY() bool {
 	fi, err := os.Stderr.Stat()
 	if err != nil {
 		return false
 	}
+
 	return fi.Mode()&os.ModeCharDevice != 0
 }
 
@@ -42,6 +53,7 @@ func newProgress(label string, total int64) *progress {
 	if !stderrIsTTY() {
 		return p
 	}
+
 	opts := []progressbar.Option{
 		progressbar.OptionSetWriter(os.Stderr),
 		progressbar.OptionSetDescription(label),
@@ -49,7 +61,7 @@ func newProgress(label string, total int64) *progress {
 		progressbar.OptionShowIts(),
 		progressbar.OptionSetItsString("files"),
 		progressbar.OptionSetElapsedTime(true),
-		progressbar.OptionThrottle(100 * time.Millisecond),
+		progressbar.OptionThrottle(barThrottle),
 	}
 	if total >= 0 {
 		opts = append(opts,
@@ -59,10 +71,12 @@ func newProgress(label string, total int64) *progress {
 	} else {
 		opts = append(opts,
 			progressbar.OptionSetPredictTime(false),
-			progressbar.OptionSpinnerType(14),
+			progressbar.OptionSpinnerType(walkSpinnerType),
 		)
 	}
+
 	p.bar = progressbar.NewOptions64(total, opts...)
+
 	return p
 }
 
@@ -71,8 +85,10 @@ func (p *progress) increment() {
 	p.count++
 	if p.bar != nil {
 		_ = p.bar.Add(1)
+
 		return
 	}
+
 	if time.Since(p.last) >= plainInterval {
 		p.last = time.Now()
 		fmt.Fprintln(os.Stderr, p.plainLine())
@@ -84,6 +100,7 @@ func (p *progress) warnf(format string, args ...any) {
 	if p.bar != nil {
 		_ = p.bar.Clear()
 	}
+
 	fmt.Fprintf(os.Stderr, format+"\n", args...)
 }
 
@@ -91,9 +108,12 @@ func (p *progress) warnf(format string, args ...any) {
 func (p *progress) finish() {
 	if p.bar != nil {
 		_ = p.bar.Finish()
+
 		fmt.Fprintln(os.Stderr)
+
 		return
 	}
+
 	fmt.Fprintln(os.Stderr, p.plainLine())
 }
 
@@ -104,19 +124,24 @@ func (p *progress) plainLine() string {
 		return fmt.Sprintf("%s: %d files, elapsed %s",
 			p.label, p.count, elapsed.Round(time.Second))
 	}
-	pct := 100.0
+
+	pct := float64(percentScale)
 	if p.total > 0 {
-		pct = 100 * float64(p.count) / float64(p.total)
+		pct = percentScale * float64(p.count) / float64(p.total)
 	}
+
 	rate := 0.0
 	if s := elapsed.Seconds(); s > 0 {
 		rate = float64(p.count) / s
 	}
+
 	eta := "?"
+
 	if rate > 0 && p.count <= p.total {
 		remaining := time.Duration(float64(p.total-p.count) / rate * float64(time.Second))
 		eta = remaining.Round(time.Second).String()
 	}
+
 	return fmt.Sprintf("%s: [%d/%d] %.0f%% %.0f files/s elapsed %s eta %s",
 		p.label, p.count, p.total, pct, rate,
 		elapsed.Round(time.Second), eta)