IDEA-69174 User should be able to save patch to existing file.

platform/vcs-impl/src/com/intellij/openapi/vcs/changes/patch/CreatePatchCommitExecutor.java

@@ -36,6 +36,7 @@ import com.intellij.openapi.vcs.*;
 import com.intellij.openapi.vcs.changes.*;
 import com.intellij.openapi.vcs.changes.shelf.ShelveChangesManager;
 import com.intellij.util.WaitForProgressToShow;
+import com.intellij.util.ui.UIUtil;
 import org.jdom.Element;
 import org.jetbrains.annotations.Nls;
 import org.jetbrains.annotations.NonNls;
@@ -161,9 +162,28 @@ public class CreatePatchCommitExecutor extends LocalCommitExecutor implements Pr
 
     public void execute(Collection<Change> changes, String commitMessage) {
       if (! myPanel.isOkToExecute()) {
-        Messages.showErrorDialog(myProject, VcsBundle.message("create.patch.error.title", myPanel.getError()), CommonBundle.getErrorTitle());
+        UIUtil.invokeLaterIfNeeded(new Runnable() {
+          @Override
+          public void run() {
+            Messages
+              .showErrorDialog(myProject, VcsBundle.message("create.patch.error.title", myPanel.getError()), CommonBundle.getErrorTitle());
+          }
+        });
         return;
       }
+      final String fileName = myPanel.getFileName();
+      final File file = new File(fileName).getAbsoluteFile();
+      if (file.exists()) {
+        final int[] result = new int[1];
+        UIUtil.invokeAndWaitIfNeeded(new Runnable() {
+          @Override
+          public void run() {
+            result[0] = Messages.showYesNoDialog(myProject, "File " + file.getName() + " (" + file.getParent() + ")" +
+                                " already exists.\nDo you want to overwrite it?", CommonBundle.getWarningTitle(), Messages.getWarningIcon());
+          }
+        });
+        if (Messages.NO == result[0]) return;
+      }
       myPanel.onOk();
       myCommitContext.putUserData(BaseRevisionTextPatchEP.ourPutBaseRevisionTextKey, myPanel.isStoreTexts());
       final List<FilePath> list = new ArrayList<FilePath>();
@@ -188,8 +208,6 @@ public class CreatePatchCommitExecutor extends LocalCommitExecutor implements Pr
         return;
       }
       try {
-        final String fileName = myPanel.getFileName();
-        final File file = new File(fileName).getAbsoluteFile();
         VcsConfiguration.getInstance(myProject).acceptLastCreatedPatchName(file.getName());
         PATCH_PATH = file.getParent();
         final boolean reversePatch = myPanel.isReversePatch();

platform/vcs-impl/src/com/intellij/openapi/vcs/changes/patch/CreatePatchConfigurationPanel.java

@@ -71,6 +71,7 @@ public class CreatePatchConfigurationPanel {
   private SelectFilesToAddTextsToPatchPanel mySelectFilesToAddTextsToPatchPanel;
   private HideableTitledPanel myHideableTitledPanel;
   private JPanel myPanelWithSelectedFiles;
+  private boolean myExecute;
 
   public CreatePatchConfigurationPanel(final Project project) {
     myProject = project;
@@ -212,8 +213,9 @@ public class CreatePatchConfigurationPanel {
     else {
       myErrorLabel.setText(patchNameChecker.getError());
     }
+    myExecute = patchNameChecker.nameOk() || !patchNameChecker.isPreventsOk();
     if (myOkEnabledListener != null) {
-      myOkEnabledListener.consume(patchNameChecker.nameOk());
+      myOkEnabledListener.consume(myExecute);
     }
   }
 
@@ -258,7 +260,7 @@ public class CreatePatchConfigurationPanel {
   }
 
   public boolean isOkToExecute() {
-    return myErrorLabel.getText() == null || myErrorLabel.getText().length() == 0;
+    return myExecute;
   }
 
   public String getError() {

platform/vcs-impl/src/com/intellij/openapi/vcs/changes/patch/PatchNameChecker.java

@@ -20,28 +20,37 @@ import java.io.File;
 public class PatchNameChecker {
   public final static int MAX = 100;
   private final String myName;
+  private boolean myPreventsOk;
   private String myError;
   private final String myPath;
 
   public PatchNameChecker(final String name) {
     myPath = name;
     myName = new File(name).getName();
+    myPreventsOk = false;
   }
 
   public boolean nameOk() {
     if (myName == null || myName.length() == 0) {
       myError = "File name cannot be empty";
+      myPreventsOk = true;
       return false;
     } else if (myName.length() > MAX) {
       myError = "File name length cannot exceed " + MAX + " characters";
+      myPreventsOk = true;
       return false;
     } else if (new File(myPath).exists()) {
       myError = "File with the same name already exists";
+      myPreventsOk = false;
       return false;
     }
     return true;
   }
 
+  public boolean isPreventsOk() {
+    return myPreventsOk;
+  }
+
   public String getError() {
     return myError;
   }