[hg]: allow to switch off hg ignored files processing

* IDEA-174155 - add registry key to avoid hg status --ignored command
 for a large number of files;

platform/util/resources/misc/registry.properties

@@ -883,7 +883,7 @@ git.diff.renameLimit.infinity.description=Sets diff.renameLimit configuration va
   If option is set to false, diff.renameLimit is taken from Git configuration (it is usually not zero by default).\
   Switching this option off may prevent Git from detecting renames in large commits in the file history.
 
-hg4idea.process.ignored=false
+hg4idea.process.ignored=true
 hg4idea.process.ignored.description=Process and highlight mercurial ignored files. \
    Switching on this option may lead to some performance problems.
 

plugins/hg4idea/src/org/zmlx/hg4idea/provider/HgLocalIgnoredHolder.java

@@ -18,6 +18,7 @@ package org.zmlx.hg4idea.provider;
 import com.intellij.dvcs.repo.AsyncFilesManagerListener;
 import com.intellij.openapi.Disposable;
 import com.intellij.openapi.diagnostic.Logger;
+import com.intellij.openapi.util.registry.Registry;
 import com.intellij.openapi.vcs.FilePath;
 import com.intellij.openapi.vcs.VcsException;
 import com.intellij.openapi.vfs.VirtualFile;
@@ -59,22 +60,24 @@ public class HgLocalIgnoredHolder implements Disposable {
   }
 
   public void startRescan() {
-    myUpdateQueue.queue(new Update("hgRescanIgnored") {
-      @Override
-      public boolean canEat(Update update) {
-        return true;
-      }
-
-      @Override
-      public void run() {
-        if (myInUpdateMode.compareAndSet(false, true)) {
-          fireUpdateStarted();
-          rescanAllIgnored();
-          myInUpdateMode.set(false);
-          fireUpdateFinished();
+    if (Registry.is("hg4idea.process.ignored")) {
+      myUpdateQueue.queue(new Update("hgRescanIgnored") {
+        @Override
+        public boolean canEat(Update update) {
+          return true;
         }
-      }
-    });
+
+        @Override
+        public void run() {
+          if (myInUpdateMode.compareAndSet(false, true)) {
+            fireUpdateStarted();
+            rescanAllIgnored();
+            myInUpdateMode.set(false);
+            fireUpdateFinished();
+          }
+        }
+      });
+    }
   }
 
   private void fireUpdateStarted() {