Apply insteadOf to raw remote URLs in addition to remote names

This also retools FugitiveRemoteUrl() argument handling to be a bit more
flexible.

autoload/fugitive.vim

@@ -886,11 +886,28 @@ function! s:ConfigLengthSort(i1, i2) abort
 endfunction
 
 function! fugitive#RemoteUrl(...) abort
-  let dir = a:0 > 1 ? s:Dir(a:2) : s:Dir()
+  let args = a:000
-  let url = !a:0 || a:1 =~# '^\.\=$' ? s:Remote(dir) : a:1
+  if a:0 && type(a:1) !=# type('')
+    let config = fugitive#Config(a:1)
+    let args = a:000[1:-1]
+  elseif a:0 > 1
+    let config = fugitive#Config(a:2)
+    let args = [a:1] + a:000[2:-1]
+  else
+    let config = fugitive#Config()
+    let args = copy(a:000)
+  endif
+  if empty(args)
+    let url = s:Remote(config)
+  elseif args[0] =~# '^\.\=$'
+    call remove(args, 0)
+    let url = s:Remote(config)
+  else
+    let url = remove(args, 0)
+  endif
   if url !~# ':\|^/\|^\.\.\=/'
-    let config = fugitive#Config(a:0 > 1 ? a:2 : s:Dir())
     let url = FugitiveConfigGet('remote.' . url . '.url', config)
+  endif
   let instead_of = []
   for [k, vs] in items(fugitive#ConfigGetRegexp('^url\.\zs.\{-\}\ze\.insteadof$', config))
     for v in vs
@@ -904,8 +921,7 @@ function! fugitive#RemoteUrl(...) abort
       break
     endif
   endfor
-  endif
+  if !index(args, 1) && !index(args, get(v:, 'true', 1)) && !index(args, 'noresolve')
-  if !get(a:, 3, 0)
     let url = fugitive#ResolveRemote(url)
   endif
   return url

plugin/fugitive.vim

@@ -171,7 +171,7 @@ endfunction
 " An optional second argument provides the Git dir, or the buffer number of a
 " buffer with a Git dir.  The default is the current buffer.
 function! FugitiveRemoteUrl(...) abort
-  return fugitive#RemoteUrl(a:0 ? a:1 : '', a:0 > 1 ? a:2 : -1, a:0 > 2 ? a:3 : 0)
+  return call('fugitive#RemoteUrl', a:000)
 endfunction
 
 " FugitiveHead() retrieves the name of the current branch. If the current HEAD