Include non-redundant separators in the hash for Path

Author: zanieb

Diff for: library/std/src/path.rs

@@ -3109,17 +3109,25 @@ impl Hash for Path {
                     bytes_hashed += to_hash.len();
                 }
 
-                // skip over separator and optionally a following CurDir item
+                // Skip over separators and, optionally, a following CurDir item
                 // since components() would normalize these away.
                 component_start = i + 1;
 
                 let tail = &bytes[component_start..];
 
                 if !verbatim {
                     component_start += match tail {
+                        [] => 0, // Do not hash a trailing separator
                         [b'.'] => 1,
                         [b'.', sep @ _, ..] if is_sep_byte(*sep) => 1,
-                        _ => 0,
+                        _ => {
+                            // Hash the first separator so we can distinguish between
+                            // `foo/bar` and `foobar`
+                            let to_hash = &[b'/' as u8];
+                            h.write(to_hash);
+                            bytes_hashed += to_hash.len();
+                            0
+                        }
                     };
                 }
             }