Git: Make checkout asynchronous

It can be slow when many files are replaced.

Change-Id: I308698ef36973374f4526107fbda0d9ad907e707
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/git/branchmodel.cpp

@@ -529,7 +529,7 @@ void BranchModel::checkoutBranch(const QModelIndex &idx)
 
     // No StashGuard since this function for now is only used with clean working dir.
     // If it is ever used from another place, please add StashGuard here
-    m_client->synchronousCheckout(m_workingDirectory, branch);
+    m_client->checkout(m_workingDirectory, branch, GitClient::StashMode::NoStash);
 }
 
 bool BranchModel::branchIsMerged(const QModelIndex &idx)

src/plugins/git/gerrit/gerritplugin.cpp

@@ -254,7 +254,7 @@ void FetchContext::cherryPick()
 
 void FetchContext::checkout()
 {
-    GitPlugin::client()->stashAndCheckout(m_repository, "FETCH_HEAD");
+    GitPlugin::client()->checkout(m_repository, "FETCH_HEAD");
 }
 
 void FetchContext::terminate()

src/plugins/git/gitclient.cpp

@@ -1113,21 +1113,22 @@ VcsBaseEditorWidget *GitClient::annotate(
     return editor;
 }
 
-bool GitClient::synchronousCheckout(const QString &workingDirectory,
-                                          const QString &ref,
-                                          QString *errorMessage)
+void GitClient::checkout(const QString &workingDirectory, const QString &ref,
+                         StashMode stashMode)
 {
+    if (stashMode == StashMode::TryStash && !beginStashScope(workingDirectory, "Checkout"))
+        return;
     QStringList arguments = setupCheckoutArguments(workingDirectory, ref);
-    const SynchronousProcessResponse resp = vcsFullySynchronousExec(
-                workingDirectory, arguments, VcsCommand::ExpectRepoChanges);
-    VcsOutputWindow::append(resp.stdOut());
-    if (resp.result == SynchronousProcessResponse::Finished) {
-        updateSubmodulesIfNeeded(workingDirectory, true);
-        return true;
-    } else {
-        msgCannotRun(arguments, workingDirectory, resp.stdErr(), errorMessage);
-        return false;
-    }
+    VcsCommand *command = vcsExec(
+                workingDirectory, arguments, nullptr, true,
+                VcsCommand::ExpectRepoChanges | VcsCommand::ShowSuccessMessage);
+    connect(command, &VcsCommand::finished,
+            this, [this, workingDirectory, stashMode](bool success) {
+        if (stashMode == StashMode::TryStash)
+            endStashScope(workingDirectory);
+        if (success)
+            updateSubmodulesIfNeeded(workingDirectory, true);
+    });
 }
 
 /* method used to setup arguments for checkout, in case user wants to create local branch */
@@ -1358,16 +1359,6 @@ bool GitClient::synchronousCheckoutFiles(const QString &workingDirectory, QStrin
     return true;
 }
 
-bool GitClient::stashAndCheckout(const QString &workingDirectory, const QString &ref)
-{
-    if (!beginStashScope(workingDirectory, "Checkout"))
-        return false;
-    if (!synchronousCheckout(workingDirectory, ref))
-        return false;
-    endStashScope(workingDirectory);
-    return true;
-}
-
 static inline QString msgParentRevisionFailed(const QString &workingDirectory,
                                               const QString &revision,
                                               const QString &why)

src/plugins/git/gitclient.h

@@ -173,10 +173,9 @@ public:
     bool synchronousCheckoutFiles(const QString &workingDirectory, QStringList files = QStringList(),
                                   QString revision = QString(), QString *errorMessage = nullptr,
                                   bool revertStaging = true);
-    // Checkout ref
-    bool stashAndCheckout(const QString &workingDirectory, const QString &ref);
-    bool synchronousCheckout(const QString &workingDirectory, const QString &ref,
-                             QString *errorMessage = nullptr);
+    enum class StashMode { NoStash, TryStash };
+    void checkout(const QString &workingDirectory, const QString &ref,
+                  StashMode stashMode = StashMode::TryStash);
 
     QStringList setupCheckoutArguments(const QString &workingDirectory, const QString &ref);
     void updateSubmodulesIfNeeded(const QString &workingDirectory, bool prompt);

src/plugins/git/giteditor.cpp

@@ -191,7 +191,7 @@ void GitEditorWidget::setPlainText(const QString &text)
 
 void GitEditorWidget::checkoutChange()
 {
-    GitPlugin::client()->stashAndCheckout(sourceWorkingDirectory(), m_currentChange);
+    GitPlugin::client()->checkout(sourceWorkingDirectory(), m_currentChange);
 }
 
 void GitEditorWidget::resetChange(const QByteArray &resetType)

src/plugins/git/gitplugin.cpp

@@ -861,7 +861,7 @@ void GitPlugin::startChangeRelatedAction(const Id &id)
         m_gitClient->synchronousRevert(workingDirectory, change);
         break;
     case Checkout:
-        m_gitClient->stashAndCheckout(workingDirectory, change);
+        m_gitClient->checkout(workingDirectory, change);
         break;
     default:
         return;