New menu command: Run a system command in this directory. (#1214)

* New menu command: Run system command in this directory.

* Echo the output from the system command.

* Update version number in change log.

* Address Vim linter message: change "\n" to nr2char(10)

* Use single quoted strings.

* Use system() instead of systemlist() for greater version compatibility.

systemlist() was introduced sometime in Vim 8+, so I switched to
system() for 7.4 compatibility.

nerdtree_plugin/fs_menu.vim

@@ -49,6 +49,10 @@ else
     call NERDTreeAddMenuItem({'text': '(l)ist the current node', 'shortcut': 'l', 'callback': 'NERDTreeListNodeWin32'})
 endif
 
+if exists('*system')
+    call NERDTreeAddMenuItem({'text': 'Run (s)ystem command in this directory', 'shortcut':'s', 'callback': 'NERDTreeSystemCommand'})
+endif
+
 "FUNCTION: s:inputPrompt(action){{{1
 "returns the string that should be prompted to the user for the given action
 "
@@ -460,4 +464,21 @@ function! NERDTreeExecuteFileWindows()
     call system('cmd.exe /c start "" ' . shellescape(l:node.path.str()))
 endfunction
 
+" FUNCTION: NERDTreeSystemCommand() {{{1
+function! NERDTreeSystemCommand()
+    let l:node = g:NERDTreeFileNode.GetSelected()
+
+    if empty(l:node)
+        return
+    endif
+
+    let l:cwd = getcwd()
+    let l:directory = l:node.path.isDirectory ? l:node.path.str() : l:node.parent.path.str()
+    execute 'cd '.l:directory
+
+    let l:nl = nr2char(10)
+    echo l:nl . system(input(l:directory . (nerdtree#runningWindows() ? '> ' : ' $ ')))
+    execute 'cd '.l:cwd
+endfunction
+
 " vim: set sw=4 sts=4 et fdm=marker: