path/filepath: deprecate HasPrefix

Use the new "Deprecated:" syntax for all instances of HasPrefix.
This is a follow-up to http://golang.org/cl/28413 which only modified path_unix.go.

In this CL, we avoid mentioning that strings.HasPrefix should be used since
that function is still subtly wrong in security applications.

See http://golang.org/cl/5712045 for more information.

Fixes #18355

Change-Id: I0d0306152cd0b0ea5110774c2c78117515b9f5cd
Reviewed-on: https://go-review.googlesource.com/34554
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/path/filepath/path_plan9.go

@@ -18,6 +18,9 @@ func volumeNameLen(path string) int {
 }
 
 // HasPrefix exists for historical compatibility and should not be used.
+//
+// Deprecated: HasPrefix does not respect path boundaries and
+// does not ignore case when required.
 func HasPrefix(p, prefix string) bool {
 	return strings.HasPrefix(p, prefix)
 }

src/path/filepath/path_unix.go

@@ -21,7 +21,8 @@ func volumeNameLen(path string) int {
 
 // HasPrefix exists for historical compatibility and should not be used.
 //
-// Deprecated: Use strings.HasPrefix instead.
+// Deprecated: HasPrefix does not respect path boundaries and
+// does not ignore case when required.
 func HasPrefix(p, prefix string) bool {
 	return strings.HasPrefix(p, prefix)
 }

src/path/filepath/path_windows.go

@@ -65,6 +65,9 @@ func volumeNameLen(path string) int {
 }
 
 // HasPrefix exists for historical compatibility and should not be used.
+//
+// Deprecated: HasPrefix does not respect path boundaries and
+// does not ignore case when required.
 func HasPrefix(p, prefix string) bool {
 	if strings.HasPrefix(p, prefix) {
 		return true