Add g:vundle_git_options, allow you to pass command line options to git client.

autoload/vundle/installer.vim

@@ -212,17 +212,22 @@ endf
 
 func! s:sync(bang, bundle) abort
   let git_dir = expand(a:bundle.path().'/.git/', 1)
+  let git_cmd = 'git'
+  if exists("g:vundle_git_options")
+    let git_cmd = git_cmd.' '.g:vundle_git_options
+    echo git_cmd
+  endif
   if isdirectory(git_dir) || filereadable(expand(a:bundle.path().'/.git', 1))
     if !(a:bang) | return 'todate' | endif
-    let cmd = 'cd '.shellescape(a:bundle.path()).' && git pull && git submodule update --init --recursive'
+    let cmd = 'cd '.shellescape(a:bundle.path()).' && '.git_cmd.' pull && '.git_cmd.' submodule update --init --recursive'
 
     let cmd = g:shellesc_cd(cmd)
 
-    let get_current_sha = 'cd '.shellescape(a:bundle.path()).' && git rev-parse HEAD'
+    let get_current_sha = 'cd '.shellescape(a:bundle.path()).' && '.git_cmd.' rev-parse HEAD'
     let get_current_sha = g:shellesc_cd(get_current_sha)
     let initial_sha = s:system(get_current_sha)[0:15]
   else
-    let cmd = 'git clone --recursive '.shellescape(a:bundle.uri).' '.shellescape(a:bundle.path())
+    let cmd = git_cmd.' clone --recursive '.shellescape(a:bundle.uri).' '.shellescape(a:bundle.path())
     let initial_sha = ''
   endif