move a couple of functions into NERDTreeCreator

The "next buffer name" functions are only used in NERDTreeCreator so put
them there.

autoload/nerdtree.vim

@@ -33,11 +33,6 @@ function! nerdtree#bufInWindows(bnum)
     return cnt
 endfunction
 
-" FUNCTION: nerdtree#bufNamePrefix() {{{2
-function! nerdtree#bufNamePrefix()
-    return 'NERD_tree_'
-endfunction
-
 "FUNCTION: nerdtree#checkForBrowse(dir) {{{2
 "inits a secondary nerd tree in the current buffer if appropriate
 function! nerdtree#checkForBrowse(dir)
@@ -232,25 +227,6 @@ function! nerdtree#invokeKeyMap(key)
     call g:NERDTreeKeyMap.Invoke(a:key)
 endfunction
 
-" FUNCTION: nerdtree#nextBufferName() {{{2
-" returns the buffer name for the next nerd tree
-function! nerdtree#nextBufferName()
-    let name = nerdtree#bufNamePrefix() . nerdtree#nextBufferNumber()
-    return name
-endfunction
-
-" FUNCTION: nerdtree#nextBufferNumber() {{{2
-" the number to add to the nerd tree buffer name to make the buf name unique
-function! nerdtree#nextBufferNumber()
-    if !exists("s:nextBufNum")
-        let s:nextBufNum = 1
-    else
-        let s:nextBufNum += 1
-    endif
-
-    return s:nextBufNum
-endfunction
-
 " FUNCTION: nerdtree#postSourceActions() {{{2
 function! nerdtree#postSourceActions()
     call g:NERDTreeBookmark.CacheBookmarks(0)

plugin/NERD_tree.vim

@@ -161,10 +161,10 @@ command! -n=0 -bar NERDTreeCWD call NERDTreeCWD()
 "============================================================
 augroup NERDTree
     "Save the cursor position whenever we close the nerd tree
-    exec "autocmd BufWinLeave ". nerdtree#bufNamePrefix() ."* call nerdtree#saveScreenState()"
+    exec "autocmd BufWinLeave ". g:NERDTreeCreator.BufNamePrefix() ."* call nerdtree#saveScreenState()"
 
     "disallow insert mode in the NERDTree
-    exec "autocmd BufEnter ". nerdtree#bufNamePrefix() ."* stopinsert"
+    exec "autocmd BufEnter ". g:NERDTreeCreator.BufNamePrefix() ."* stopinsert"
 augroup END
 
 if g:NERDTreeHijackNetrw

plugin/nerdtree/creator.vim

@@ -27,6 +27,11 @@ function! s:Creator._broadcastInitEvent()
     silent doautocmd User NERDTreeInit
 endfunction
 
+" FUNCTION: s:Creator.BufNamePrefix() {{{2
+function! s:Creator.BufNamePrefix()
+    return 'NERD_tree_'
+endfunction
+
 "FUNCTION: s:Creator.CreatePrimary(a:name) {{{1
 function! s:Creator.CreatePrimary(name)
     let creator = s:Creator.New()
@@ -91,7 +96,7 @@ function! s:Creator.createSecondary(dir)
 
     "we need a unique name for each secondary tree buffer to ensure they are
     "all independent
-    exec "silent edit " . nerdtree#nextBufferName()
+    exec "silent edit " . self._nextBufferName()
 
     let b:NERDTreePreviousBuf = bufnr(previousBuf)
 
@@ -174,7 +179,7 @@ function! s:Creator._createTreeWin()
     let splitSize = g:NERDTreeWinSize
 
     if !exists('t:NERDTreeBufName')
-        let t:NERDTreeBufName = nerdtree#nextBufferName()
+        let t:NERDTreeBufName = self._nextBufferName()
         silent! exec splitLocation . 'vertical ' . splitSize . ' new'
         silent! exec "edit " . t:NERDTreeBufName
     else
@@ -192,6 +197,25 @@ function! s:Creator.New()
     return newCreator
 endfunction
 
+" FUNCTION: s:Creator._nextBufferName() {{{2
+" returns the buffer name for the next nerd tree
+function! s:Creator._nextBufferName()
+    let name = s:Creator.BufNamePrefix() . self._nextBufferNumber()
+    return name
+endfunction
+
+" FUNCTION: s:Creator._nextBufferNumber() {{{2
+" the number to add to the nerd tree buffer name to make the buf name unique
+function! s:Creator._nextBufferNumber()
+    if !exists("s:Creator._NextBufNum")
+        let s:Creator._NextBufNum = 1
+    else
+        let s:Creator._NextBufNum += 1
+    endif
+
+    return s:Creator._NextBufNum
+endfunction
+
 "FUNCTION: s:Creator._pathForString(str) {{{1
 "find a bookmark or adirectory for the given string
 function! s:Creator._pathForString(str)