Added Case Sensitive Move Operation via newly introduced flag NERDTreeCaseSensitiveFS (#1375)

* Added NERDTreeCaseInsensitiveFS option.

* check against g:NERDTreeCaseInsensitiveFS with path.equals method

* Fixed issues in comments and added nerdtree#runningMac

* Using nerdtree#runningMac instead of manual checks for mac

* Better implementation

* Updated documentation

* Added notice about the flag

* Updated the documentation

* Added support for g:NERDTreeCaseSensitiveFS = 3

* Better comments

* Exported caseSensitiveFS check as a function

nerdtree_plugin/fs_menu.vim

@@ -23,7 +23,7 @@ call NERDTreeAddMenuItem({'text': '(a)dd a childnode', 'shortcut': 'a', 'callbac
 call NERDTreeAddMenuItem({'text': '(m)ove the current node', 'shortcut': 'm', 'callback': 'NERDTreeMoveNode'})
 call NERDTreeAddMenuItem({'text': '(d)elete the current node', 'shortcut': 'd', 'callback': 'NERDTreeDeleteNode'})
 
-if has('gui_mac') || has('gui_macvim') || has('mac')
+if nerdtree#runningMac()
     call NERDTreeAddMenuItem({'text': '(r)eveal in Finder the current node', 'shortcut': 'r', 'callback': 'NERDTreeRevealInFinder'})
     call NERDTreeAddMenuItem({'text': '(o)pen the current node with system editor', 'shortcut': 'o', 'callback': 'NERDTreeExecuteFile'})
     call NERDTreeAddMenuItem({'text': '(q)uicklook the current node', 'shortcut': 'q', 'callback': 'NERDTreeQuickLook'})
@@ -149,21 +149,41 @@ function! s:renameBuffer(bufNum, newNodeName, isDirectory)
         let quotedFileName = fnameescape(a:newNodeName)
         let editStr = g:NERDTreePath.New(a:newNodeName).str({'format': 'Edit'})
     endif
-    " 1. ensure that a new buffer is loaded
-    call nerdtree#exec('badd ' . quotedFileName, 0)
-    " 2. ensure that all windows which display the just deleted filename
-    " display a buffer for a new filename.
     let s:originalTabNumber = tabpagenr()
     let s:originalWindowNumber = winnr()
-    call nerdtree#exec('tabdo windo if winbufnr(0) ==# ' . a:bufNum . " | exec ':e! " . editStr . "' | endif", 0)
-    call nerdtree#exec('tabnext ' . s:originalTabNumber, 1)
-    call nerdtree#exec(s:originalWindowNumber . 'wincmd w', 1)
-    " 3. We don't need a previous buffer anymore
+    let l:tempBufferName = 'NERDTreeRenameTempBuffer'
+
+    " 1. swap deleted file buffer with a temporary one
+    " this step is needed to compensate for case insensitive filesystems
+
+    " 1.1. create an intermediate(temporary) buffer
+    call nerdtree#exec('badd ' . l:tempBufferName, 0)
+    let l:tempBufNum = bufnr(l:tempBufferName)
+    " 1.2. ensure that all windows which display the just deleted filename
+    " display the new temp buffer.
+    call nerdtree#exec('tabdo windo if winbufnr(0) ==# ' . a:bufNum . " | exec ':e! " . l:tempBufferName . "' | endif", 0)
+    " 1.3. We don't need the deleted file buffer anymore
     try
         call nerdtree#exec('confirm bwipeout ' . a:bufNum, 0)
     catch
         " This happens when answering Cancel if confirmation is needed. Do nothing.
     endtry
+
+    " 2. swap temporary buffer with the new filename buffer
+    " 2.1. create the actual new file buffer
+    call nerdtree#exec('badd ' . quotedFileName, 0)
+
+    " 2.2. ensure that all windows which display the temporary buffer
+    " display a buffer for the new filename.
+    call nerdtree#exec('tabdo windo if winbufnr(0) ==# ' . l:tempBufNum . " | exec ':e! " . editStr . "' | endif", 0)
+    call nerdtree#exec('tabnext ' . s:originalTabNumber, 1)
+    call nerdtree#exec(s:originalWindowNumber . 'wincmd w', 1)
+    " 2.3. We don't need the temporary buffer anymore
+    try
+        call nerdtree#exec('confirm bwipeout ' . l:tempBufNum, 0)
+    catch
+        " This happens when answering Cancel if confirmation is needed. Do nothing.
+    endtry
 endfunction
 
 "FUNCTION: NERDTreeAddNode(){{{1
@@ -206,7 +226,24 @@ function! NERDTreeMoveNode()
     let prompt = s:inputPrompt('move')
     let newNodePath = input(prompt, curNode.path.str(), 'file')
     while filereadable(newNodePath)
-        call nerdtree#echoWarning('This destination already exists. Try again.')
+        " allow renames with different casing when g:NERDTreeCaseSensitiveFS
+        " is set to either 0 or 3 and the 2 paths are equal
+        if (g:NERDTreeCaseSensitiveFS == 0 || g:NERDTreeCaseSensitiveFS == 3) &&
+                    \nerdtree#pathEquals(curNode.path.str(), newNodePath)
+            break
+        endif
+
+        call nerdtree#echoWarning('This destination already exists, Try again.')
+
+        " inform the user about the flag if we think it is a false positive
+        " when g:NERDTreeCaseSensitiveFS is set to 2
+        if g:NERDTreeCaseSensitiveFS == 2 &&
+                    \!nerdtree#osDefaultCaseSensitiveFS() &&
+                    \nerdtree#pathEquals(curNode.path.str(), newNodePath)
+            echon "\n(If it is a false positive please consider assigning NERDTreeCaseSensitiveFS's value)"
+        endif
+
+        " prompt the user again
         let newNodePath = substitute(input(prompt, curNode.path.str(), 'file'), '\(^\s*\|\s*$\)', '', 'g')
     endwhile