Git: show commit given as command line parameter in diff editor

ex: qtcreator -client -git-show d3eb585db9 from qt-creator source dir.

Change-Id: Ice62f062d431d2ab74e3d6832dfc8b0b555dfa19
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: André Hartmann <aha_1980@gmx.de>

src/plugins/git/Git.json.in

@@ -15,6 +15,13 @@
     \"Category\" : \"Version Control\",
     \"Description\" : \"Git integration.\",
     \"Url\" : \"http://www.qt.io\",
+    \"Arguments\" : [
+        {
+            \"Name\" : \"-git-show\",
+            \"Parameter\" : \"git commit hash\",
+            \"Description\" : \"Show given commit hash\"
+        }
+    ],
     $$dependencyList,
 
     \"Mimetypes\" : [

src/plugins/git/gitplugin.cpp

@@ -289,7 +289,6 @@ QAction *GitPlugin::createRepositoryAction(ActionContainer *ac, const QString &t
 
 bool GitPlugin::initialize(const QStringList &arguments, QString *errorMessage)
 {
-    Q_UNUSED(arguments)
     Q_UNUSED(errorMessage)
 
     Context context(Constants::GIT_CONTEXT);
@@ -668,6 +667,12 @@ bool GitPlugin::initialize(const QStringList &arguments, QString *errorMessage)
     m_gerritPlugin->updateActions(currentState());
     m_gerritPlugin->addToLocator(m_commandLocator);
 
+    auto cmdContext = new QObject(this);
+    connect(Core::ICore::instance(), &Core::ICore::coreOpened, cmdContext, [this, cmdContext, arguments] {
+        remoteCommand(arguments, QDir::currentPath(), {});
+        cmdContext->deleteLater();
+    });
+
     return ok;
 }
 
@@ -1418,6 +1423,17 @@ void GitPlugin::updateBranches(const QString &repository)
         m_branchDialog->refreshIfSame(repository);
 }
 
+QObject *GitPlugin::remoteCommand(const QStringList &options, const QString &workingDirectory,
+                                  const QStringList &)
+{
+    if (!m_gitClient || options.size() < 2)
+        return nullptr;
+
+    if (options.first() == "-git-show")
+        m_gitClient->show(workingDirectory, options.at(1));
+    return nullptr;
+}
+
 void GitPlugin::updateRepositoryBrowserAction()
 {
     const bool repositoryEnabled = currentState().hasTopLevel();

src/plugins/git/gitplugin.h

@@ -89,6 +89,9 @@ public:
     void startCommit(CommitType commitType = SimpleCommit);
     void updateBranches(const QString &repository);
 
+    QObject *remoteCommand(const QStringList &options, const QString &workingDirectory,
+                           const QStringList &args) override;
+
 protected:
     void updateActions(VcsBase::VcsBasePlugin::ActionState) override;
     bool submitEditorAboutToClose() override;