git: collect affected files from correct stdout/err stream

When the message is detected (e.g.
"untracked working tree files would be overwritten by merge"),
remember the output type, and read the files only from the stream
of that type.

Before that, since stdout and stderr are reported asynchronously,
messages could arrive like that:
    error: The following untracked working tree files would be overwritten by merge: 
    Updating 48295bf..cfba4dc 
    untracked.txt
And we treated "Updating..." as a file.

This caused blinking of the GitBranchWorkerTest.

Also add some debug logging for possible future needs.

plugins/git4idea/src/git4idea/commands/GitLocalChangesWouldBeOverwrittenDetector.java

@@ -48,9 +48,8 @@ public class GitLocalChangesWouldBeOverwrittenDetector extends GitMessageWithFil
   )};
 
   // common for checkout and merge
-  public static final Event NEW_PATTERN = new Event(
-    "Your local changes to the following files would be overwritten by",
-    "commit your changes or stash them before");
+  public static final Event NEW_PATTERN = new Event("LocalChangesDetector",
+    "Your local changes to the following files would be overwritten by", "commit your changes or stash them before");
 
   @NotNull private final Operation myOperation;
 

plugins/git4idea/src/git4idea/commands/GitMessageWithFilesDetector.java

@@ -15,10 +15,12 @@
  */
 package git4idea.commands;
 
+import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.util.Key;
 import com.intellij.openapi.util.io.FileUtil;
 import com.intellij.openapi.vfs.VirtualFile;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -26,22 +28,22 @@ import java.util.HashSet;
 import java.util.Set;
 
 /**
- * The listener of {@link git4idea.commands.GitLineHandler} which watches Git output and detects some message in console,
+ * The listener of {@link GitLineHandler} which watches Git output and detects some message in console,
  * captures the following list of files and stops saving them when another message occurs.
  *
  * For example, the situation, when local changes would be overwritten by checkout.
  *
  * @see GitSimpleEventDetector
- * @author Kirill Likhodedov
  */
 public class GitMessageWithFilesDetector implements GitLineHandlerListener {
+  private static final Logger LOG = Logger.getInstance(GitMessageWithFilesDetector.class);
 
-  private final Event myEvent;
-  private final VirtualFile myRoot;
+  @NotNull private final Event myEvent;
+  @NotNull private final VirtualFile myRoot;
 
-  protected final Set<String> myAffectedFiles = new HashSet<>();
-  protected boolean myMessageDetected;
-  private boolean myFilesAreDisplayed;
+  @NotNull protected final Set<String> myAffectedFiles = new HashSet<>();
+  protected volatile boolean myMessageDetected;
+  @Nullable private volatile Key myMessageOutputType;
 
   public GitMessageWithFilesDetector(@NotNull Event event, @NotNull VirtualFile root) {
     myEvent = event;
@@ -51,15 +53,21 @@ public class GitMessageWithFilesDetector implements GitLineHandlerListener {
   @Override
   public void onLineAvailable(@NotNull String line, @NotNull Key outputType) {
     if (line.contains(myEvent.getMessageStartMarker())) {
+      LOG.debug("|" + myEvent.name + "| message start marker detected in [" + line + "]" + "of type " + outputType);
       myMessageDetected = true;
-      myFilesAreDisplayed = true;
+      myMessageOutputType = outputType;
     }
     else if (line.contains(myEvent.getMessageEndMarker())) {
-      myFilesAreDisplayed = false;
+      LOG.debug("|" + myEvent.name + "| message end marker detected in [" + line + "]" + "of type " + outputType);
+      myMessageOutputType = null;
     }
-    else if (myFilesAreDisplayed) {
+    else if (outputType.equals(myMessageOutputType)) {
+      LOG.debug("|" + myEvent.name + "| Treating as a file: [" + line + "]" + "of type " + outputType);
       myAffectedFiles.add(line.trim());
     }
+    else {
+      LOG.debug("|" + myEvent.name + "| Plain message: [" + line + "]" + "of type " + outputType);
+    }
   }
 
   @Override
@@ -98,21 +106,24 @@ public class GitMessageWithFilesDetector implements GitLineHandlerListener {
   }
 
   public static class Event {
-    private final String myMessageStartMarker;
-    private final String myMessageEndMarker;
+    @NotNull private final String name;
+    @NotNull private final String myMessageStartMarker;
+    @NotNull private final String myMessageEndMarker;
 
-    Event(String messageStartMarker, String messageEndMarker) {
+    Event(@NotNull String eventName, @NotNull String messageStartMarker, @NotNull String messageEndMarker) {
+      name = eventName;
       myMessageStartMarker = messageStartMarker;
       myMessageEndMarker = messageEndMarker;
     }
 
+    @NotNull
     public String getMessageStartMarker() {
       return myMessageStartMarker;
     }
 
+    @NotNull
     public String getMessageEndMarker() {
       return myMessageEndMarker;
     }
   }
-
 }

plugins/git4idea/src/git4idea/commands/GitUntrackedFilesOverwrittenByOperationDetector.java

@@ -37,6 +37,7 @@ public class GitUntrackedFilesOverwrittenByOperationDetector extends GitMessageW
   );
 
   private static final Event NEW_UNTRACKED_FILES_OVERWRITTEN_BY = new Event(
+    "UntrackedFileDetector",
     "The following untracked working tree files would be overwritten by",
     "Please move or remove them before"
   );