refactor: improved logging on pruning

pkg/formatter/formatter.go

@@ -1,6 +1,7 @@
 package formatter
 
 import (
+	"fmt"
 	"os"
 	"strings"
 	"time"
@@ -70,3 +71,21 @@ func StripTagMeta(image string) string {
 
 	return image
 }
+
+// ByteCountSI presents a human friendly representation of a byte count. See
+// https://yourbasic.org/golang/formatting-byte-size-to-human-readable-format.
+func ByteCountSI(b uint64) string {
+	const unit = 1000
+
+	if b < unit {
+		return fmt.Sprintf("%d B", b)
+	}
+
+	div, exp := uint64(unit), 0
+	for n := b / unit; n >= unit; n /= unit {
+		div *= unit
+		exp++
+	}
+
+	return fmt.Sprintf("%.1f %cB", float64(b)/float64(div), "kMGTPE"[exp])
+}