* fix duplicated slash in s:Path.isUnder() (on windows OS) (#1122)

* * fix duplicated slash in s:Path.isUnder() (on windows OS, for root directory on drive Path.str() return path with [back]slash)

* * Rewrite NERDTreePath.isUnder() and NERDTreePath.isAncestor() for direct comparison of paths without transformations

* Remove trailing slash, so we don't end up with two on root folder.

The str() function returns "C:\" on the root folder and "C:\temp" on
non-root folders, one with and one without a trailing backslash. This
inconsistency needs to be handled so the stridx() function will work
correctly.

* Make sure the change also works in a non-windows file system.

This commit handles an edge case that can be triggered with these
commands:
    :cd /home/me
    :e /foobar.txt  (an existing file)
    :NERDTreeFind
What happened was the root directory name '/' was being Resolved(), and
the trailing (and only) slash was being removed. The NERDTree was then
created in the current working directory, instead of the root directory.
:NERDTreeFind then wasn't able to find foobar.txt, and printed an error.

* Remove degugging statements.

* * ambiguity issue fix

Co-authored-by: Phil Runninger <philrunninger@gmail.com>

CHANGELOG.md

@@ -5,6 +5,7 @@
         - **.PATCH**: Pull Request Title (PR Author) [PR Number](Link to PR)
 -->
 #### 6.7
+- **.11**: Fix exception in NERDTreeFind (on windows OS and If the file is located in the root directory of the disk)  [#1122](https://github.com/preservim/nerdtree/pull/1122)
 - **.10**: Do not consider the tree root to be "cascadable". (lifecrisis) [#1120](https://github.com/preservim/nerdtree/pull/1120)
 - **.9**: Force `:NERDTreeFocus` to allow events to be fired when switching windows. (PhilRunninger) [#1118](https://github.com/preservim/nerdtree/pull/1118)
 - **.8**: Fix example code for the `NERDTreeAddKeyMap()` function. (PhilRunninger) [#1116](https://github.com/preservim/nerdtree/pull/1116)

lib/nerdtree/creator.vim

@@ -249,7 +249,11 @@ function! s:Creator._pathForString(str)
         if dir =~# '^\.'
             let dir = getcwd() . g:NERDTreePath.Slash() . dir
         endif
-        let dir = g:NERDTreePath.Resolve(dir)
+
+        "hack to prevent removing slash if dir is the root of the file system.
+        if dir !=# '/'
+            let dir = g:NERDTreePath.Resolve(dir)
+        endif
 
         try
             let path = g:NERDTreePath.New(dir)

lib/nerdtree/path.vim

@@ -546,26 +546,36 @@ endfunction
 " return 1 if this path is somewhere above the given path in the filesystem.
 "
 " a:path should be a dir
-function! s:Path.isAncestor(path)
-    if !self.isDirectory
-        return 0
-    endif
-
-    let this = self.str()
-    let that = a:path.str()
-    return stridx(that, this) ==# 0
+function! s:Path.isAncestor(child)
+    return a:child.isUnder(self)
 endfunction
 
 " FUNCTION: Path.isUnder(path) {{{1
 " return 1 if this path is somewhere under the given path in the filesystem.
-function! s:Path.isUnder(path)
-    if a:path.isDirectory ==# 0
+function! s:Path.isUnder(parent)
+    if a:parent.isDirectory ==# 0
         return 0
     endif
-
-    let this = self.str()
-    let that = a:path.str()
-    return stridx(this, that . s:Path.Slash()) ==# 0
+    if nerdtree#runningWindows() && a:parent.drive !=# self.drive
+        return 0
+    endif
+    let l:this_count = len(self.pathSegments)
+    if l:this_count ==# 0
+        return 0
+    endif
+    let l:that_count = len(a:parent.pathSegments)
+    if l:that_count ==# 0
+        return 1
+    endif
+    if l:that_count >= l:this_count
+        return 0
+    endif
+    for i in range(0, l:that_count-1)
+        if self.pathSegments[i] !=# a:parent.pathSegments[i]
+            return 0
+        endif
+    endfor
+    return 1
 endfunction
 
 " FUNCTION: Path.JoinPathStrings(...) {{{1