archive/tar: narrow trim range for formatter'formatString

Trim s[:len(b)-1] rather than s[:len(b)], since s[len(b)-1] is '/'.

Change-Id: I055da555810c112774549bd13d4faa8bfa0a60dc
GitHub-Last-Rev: 4579775
GitHub-Pull-Request: #60729
Reviewed-on: https://go-review.googlesource.com/c/go/+/502376
Run-TryBot: Ian Lance Taylor <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: David Chase <[email protected]>

Author: callthingsoff

src/archive/tar/strconv.go

@@ -73,7 +73,7 @@ func (f *formatter) formatString(b []byte, s string) {
 	// in the V7 path field as a directory even though the full path
 	// recorded elsewhere (e.g., via PAX record) contains no trailing slash.
 	if len(s) > len(b) && b[len(b)-1] == '/' {
-		n := len(strings.TrimRight(s[:len(b)], "/"))
+		n := len(strings.TrimRight(s[:len(b)-1], "/"))
 		b[n] = 0 // Replace trailing slash with NUL terminator
 	}
 }