Properly cleanup git repos and memory on project/frame deletion

* Ensure the git backend is deleted when the project tree is deleted.
* Unload the git repo for a project when the project is unloaded from
  the tree.

common/git/kicad_git_errors.h

@@ -33,6 +33,7 @@ class KIGIT_ERRORS
 public:
 
     KIGIT_ERRORS() = default;
+    virtual ~KIGIT_ERRORS() = default;
 
     const std::vector<wxString>& GetErrorStrings() const
     {

kicad/project_tree.cpp

@@ -50,7 +50,7 @@ PROJECT_TREE::PROJECT_TREE( PROJECT_TREE_PANE* parent ) :
         m_statusImageList( nullptr )
 {
     m_projectTreePane = parent;
-    m_gitCommon = new KIGIT_COMMON( nullptr );
+    m_gitCommon = std::make_unique<KIGIT_COMMON>( nullptr );
 
     // Make sure the GUI font scales properly on GTK
     SetFont( KIUI::GetControlFont( this ) );

kicad/project_tree.h

@@ -25,6 +25,8 @@
 #ifndef PROJECT_TREE_H
 #define PROJECT_TREE_H
 
+#include <memory>
+
 #include <git/kicad_git_common.h>
 
 #include <wx/treectrl.h>
@@ -45,7 +47,7 @@ private:
     PROJECT_TREE_PANE*            m_projectTreePane;
     wxImageList*                  m_imageList;
     wxImageList*                  m_statusImageList;
-    KIGIT_COMMON*      m_gitCommon;
+    std::unique_ptr<KIGIT_COMMON> m_gitCommon;
 
 public:
     PROJECT_TREE_PANE* GetProjectTreePane() const { return m_projectTreePane; }
@@ -58,7 +60,7 @@ public:
     void SetGitRepo( git_repository* aRepo )    { m_gitCommon->SetRepo( aRepo ); }
     git_repository* GetGitRepo() const          { return m_gitCommon->GetRepo(); }
 
-    KIGIT_COMMON* GitCommon() const             { return m_gitCommon; }
+    KIGIT_COMMON* GitCommon() const             { return m_gitCommon.get(); }
 
 private:
     /* overridden sort function */

kicad/project_tree_pane.cpp

@@ -1482,6 +1482,13 @@ void PROJECT_TREE_PANE::EmptyTreePrj()
     shutdownFileWatcher();
 
     m_TreeProject->DeleteAllItems();
+
+    // Remove the git repository when the project is unloaded
+    if( m_TreeProject->GetGitRepo() )
+    {
+        git_repository_free( m_TreeProject->GetGitRepo() );
+        m_TreeProject->SetGitRepo( nullptr );
+    }
 }