path: fix normalize for absolutes

Fixes a regression introduced by
b212be08f6.

path.normalize(''/a/b/c/../../../x/y/z'') should return '/x/y/z'.

Fixes: https://github.com/nodejs/node/issues/5585
PR-URL: https://github.com/nodejs/node/pull/5589
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>

lib/path.js

@@ -44,7 +44,7 @@ function normalizeStringWin32(path, allowAboveRoot) {
               dots = 0;
               continue;
             }
-          } else if (res.length === 2) {
+          } else if (res.length === 2 || res.length === 1) {
             res = '';
             lastSlash = i;
             dots = 0;
@@ -110,7 +110,7 @@ function normalizeStringPosix(path, allowAboveRoot) {
               dots = 0;
               continue;
             }
-          } else if (res.length === 2) {
+          } else if (res.length === 2 || res.length === 1) {
             res = '';
             lastSlash = i;
             dots = 0;

test/parallel/test-path.js

@@ -377,6 +377,7 @@ assert.equal(path.win32.normalize('a//b//./c'), 'a\\b\\c');
 assert.equal(path.win32.normalize('a//b//.'), 'a\\b');
 assert.equal(path.win32.normalize('//server/share/dir/file.ext'),
              '\\\\server\\share\\dir\\file.ext');
+assert.equal(path.win32.normalize('/a/b/c/../../../x/y/z'), '\\x\\y\\z');
 
 assert.equal(path.posix.normalize('./fixtures///b/../b/c.js'),
              'fixtures/b/c.js');
@@ -384,6 +385,8 @@ assert.equal(path.posix.normalize('/foo/../../../bar'), '/bar');
 assert.equal(path.posix.normalize('a//b//../b'), 'a/b');
 assert.equal(path.posix.normalize('a//b//./c'), 'a/b/c');
 assert.equal(path.posix.normalize('a//b//.'), 'a/b');
+assert.equal(path.posix.normalize('/a/b/c/../../../x/y/z'), '/x/y/z');
+assert.equal(path.posix.normalize('///..//./foo/.//bar'), '/foo/bar');
 
 
 // path.resolve tests