From fc530ea1dc58d14850c7d72b32ae001387c19400 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Fri, 5 Jul 2019 13:49:40 +0200
Subject: [PATCH 1/2] path: using .relative() should not return a trailing
 slash

Resolving a path against root with `path.relative()` should not
include a trailing slash.

Fixes: https://github.com/nodejs/node/issues/28549
---
 lib/path.js                         | 15 ++++++++++-----
 test/parallel/test-path-relative.js |  3 ++-
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/lib/path.js b/lib/path.js
index 2301a6ebb8321f..f7a8612933ad76 100644
--- a/lib/path.js
+++ b/lib/path.js
@@ -1090,11 +1090,16 @@ const posix = {
           // For example: from='/'; to='/foo'
           return to.slice(toStart + i);
         }
-      } else if (fromLen > length &&
-                 from.charCodeAt(fromStart + i) === CHAR_FORWARD_SLASH) {
-        // We get here if `to` is the exact base path for `from`.
-        // For example: from='/foo/bar/baz'; to='/foo/bar'
-        lastCommonSep = i;
+      } else if (fromLen > length) {
+        if (from.charCodeAt(fromStart + i) === CHAR_FORWARD_SLASH) {
+          // We get here if `to` is the exact base path for `from`.
+          // For example: from='/foo/bar/baz'; to='/foo/bar'
+          lastCommonSep = i;
+        } else if (i === 0) {
+          // We get here if `to` is the root.
+          // For example: from='/foo/bar'; to='/'
+          lastCommonSep = 0;
+        }
       }
     }
 
diff --git a/test/parallel/test-path-relative.js b/test/parallel/test-path-relative.js
index 599381cdccfcb9..72f862b6df764e 100644
--- a/test/parallel/test-path-relative.js
+++ b/test/parallel/test-path-relative.js
@@ -47,7 +47,8 @@ const relativeTests = [
      ['/foo/bar/baz-quux', '/foo/bar/baz', '../baz'],
      ['/foo/bar/baz', '/foo/bar/baz-quux', '../baz-quux'],
      ['/baz-quux', '/baz', '../baz'],
-     ['/baz', '/baz-quux', '../baz-quux']
+     ['/baz', '/baz-quux', '../baz-quux'],
+     ['/page1/page2/foo', '/', '../../..']
     ]
   ]
 ];

From 58edefdc841ae33c18fa5426419d3a8847e5a827 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Fri, 5 Jul 2019 14:34:25 +0200
Subject: [PATCH 2/2] path: move branch to the correct location

This code branch only makes sense when i === length. Otherwise it'll
already be handled.
---
 lib/path.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/path.js b/lib/path.js
index f7a8612933ad76..e278c891482070 100644
--- a/lib/path.js
+++ b/lib/path.js
@@ -518,11 +518,11 @@ const win32 = {
           lastCommonSep = 3;
         }
       }
+      if (lastCommonSep === -1)
+        lastCommonSep = 0;
     }
 
     let out = '';
-    if (lastCommonSep === -1)
-      lastCommonSep = 0;
     // Generate the relative path based on the path difference between `to` and
     // `from`
     for (i = fromStart + lastCommonSep + 1; i <= fromEnd; ++i) {