Option for mixing dot files when sorting

NERDTree can now optionally ignore the dot at the beginning of hidden
filenames for sorting to show them next to normal files if
`g:NERDTreeSortHiddenFirst` is set to 0.  (By default it's set to 1 to
preserve the current behavior.)  This is just like what GNU ls does when
`LC_COLLATE` environment variable is set to `en_US`.

doc/NERD_tree.txt

@@ -620,6 +620,10 @@ NERD tree. These options should be set in your vimrc.
 |'NERDTreeCaseSensitiveSort'|   Tells the NERD tree whether to be case
                                 sensitive or not when sorting nodes.
 
+|'NERDTreeSortHiddenFirst'|     Tells the NERD tree whether to take the dot
+                                at the beginning of the hidden file names
+                                into account when sorting nodes.
+
 |'NERDTreeChDirMode'|           Tells the NERD tree if/when it should change
                                 vim's current working directory.
 

lib/nerdtree/path.vim

@@ -103,6 +103,10 @@ function! s:Path.compareTo(path)
     elseif thisSS > thatSS
         return 1
     else
+        if !g:NERDTreeSortHiddenFirst
+            let thisPath = substitute(thisPath, '^[._]', '', '')
+            let thatPath = substitute(thatPath, '^[._]', '', '')
+        endif
         "if the sort sequences are the same then compare the paths
         "alphabetically
         let pathCompare = g:NERDTreeCaseSensitiveSort ? thisPath <# thatPath : thisPath <? thatPath

plugin/NERD_tree.vim

@@ -49,6 +49,7 @@ call s:initVariable("g:NERDChristmasTree", 1)
 call s:initVariable("g:NERDTreeAutoCenter", 1)
 call s:initVariable("g:NERDTreeAutoCenterThreshold", 3)
 call s:initVariable("g:NERDTreeCaseSensitiveSort", 0)
+call s:initVariable("g:NERDTreeSortHiddenFirst", 1)
 call s:initVariable("g:NERDTreeChDirMode", 0)
 call s:initVariable("g:NERDTreeMinimalUI", 0)
 if !exists("g:NERDTreeIgnore")