Allow command modifiers for on-demand-loading commands (#1110)

Before this commit, commands like this -
	:tab Git diff HEAD^ HEAD
were interpreted like this -
	:Git diff HEAD^ HEAD
This commit fixes that issue.

Author: subnut

plug.vim

@@ -372,8 +372,10 @@ function! plug#end()
 
   for [cmd, names] in items(lod.cmd)
     execute printf(
-    \ 'command! -nargs=* -range -bang -complete=file %s call s:lod_cmd(%s, "<bang>", <line1>, <line2>, <q-args>, %s)',
-    \ cmd, string(cmd), string(names))
+    \ has('patch-7.4.1898')
+    \ ? 'command! -nargs=* -range -bang -complete=file %s call s:lod_cmd(%s, "<bang>", <line1>, <line2>, <q-args>, <q-mods> ,%s)'
+    \ : 'command! -nargs=* -range -bang -complete=file %s call s:lod_cmd(%s, "<bang>", <line1>, <line2>, <q-args>, %s)'
+    \ , cmd, string(cmd), string(names))
   endfor
 
   for [map, names] in items(lod.map)
@@ -651,11 +653,19 @@ function! s:lod_ft(pat, names)
   call s:doautocmd('filetypeindent', 'FileType')
 endfunction
 
-function! s:lod_cmd(cmd, bang, l1, l2, args, names)
-  call s:lod(a:names, ['ftdetect', 'after/ftdetect', 'plugin', 'after/plugin'])
-  call s:dobufread(a:names)
-  execute printf('%s%s%s %s', (a:l1 == a:l2 ? '' : (a:l1.','.a:l2)), a:cmd, a:bang, a:args)
-endfunction
+if has('patch-7.4.1898')
+  function! s:lod_cmd(cmd, bang, l1, l2, args, mods, names)
+    call s:lod(a:names, ['ftdetect', 'after/ftdetect', 'plugin', 'after/plugin'])
+    call s:dobufread(a:names)
+    execute printf('%s %s%s%s %s', a:mods, (a:l1 == a:l2 ? '' : (a:l1.','.a:l2)), a:cmd, a:bang, a:args)
+  endfunction
+else
+  function! s:lod_cmd(cmd, bang, l1, l2, args, names)
+    call s:lod(a:names, ['ftdetect', 'after/ftdetect', 'plugin', 'after/plugin'])
+    call s:dobufread(a:names)
+    execute printf('%s%s%s %s', (a:l1 == a:l2 ? '' : (a:l1.','.a:l2)), a:cmd, a:bang, a:args)
+  endfunction
+endif
 
 function! s:lod_map(map, names, with_prefix, prefix)
   call s:lod(a:names, ['ftdetect', 'after/ftdetect', 'plugin', 'after/plugin'])