Fix wrong function name

Author: layus

autoload/vundle/installer.vim

@@ -356,7 +356,7 @@ endf
 " return -- A 15 character log sha for the current HEAD
 " ---------------------------------------------------------------------------
 func! s:get_current_sha(bundle)
-  let cmd = s:make_sync_command(a:bundle, ['rev-parse', 'HEAD'])
+  let cmd = s:make_git_command(a:bundle, ['rev-parse', 'HEAD'])
   let out = s:system(cmd)[0:15]
   return out
 endf