Prevent serialization due to early termination of threads

plug.vim

@@ -344,14 +344,10 @@ function! s:update_parallel(pull, threads)
       logh.call
     end
   }
-  refill = proc { |name|
-    mtx.synchronize do
-      all.merge! VIM::evaluate("s:extend(['#{name}'])")
-      logh.call
-    end
-  }
-  VIM::evaluate('a:threads').to_i.times.map { |i|
-    Thread.new(i) do |ii|
+  until all.empty?
+    names = all.keys
+    [names.length, VIM::evaluate('a:threads').to_i].min.times.map { |i|
+      Thread.new(i) do
         while pair = take1.call
           name = pair.first
           dir, uri, branch = pair.last.values_at *%w[dir uri branch]
@@ -374,10 +370,12 @@ function! s:update_parallel(pull, threads)
             end
           result = result.lines.to_a.last.strip
           log.call name, result, ok
-        refill.call name
         end
       end
     }.each(&:join)
+    all.merge! VIM::evaluate("s:extend(#{names.inspect})")
+    logh.call
+  end
   $curbuf[1] = "Updated. Elapsed time: #{"%.6f" % (Time.now - st)} sec."
 EOF
 endfunction