Fix git status icons not showing when project opened via symlink

When a project is opened through a symlinked path, libgit2's
git_repository_workdir() returns the canonical path with symlinks
resolved. This caused a path mismatch between the tree cache
(which uses the user-provided symlinked path) and git status
results (which used canonical paths), preventing status icons
from being displayed.

The fix introduces SetProjectDir()/GetProjectDir() methods to
KIGIT_COMMON to store and use the user-provided project path.
A helper function computeSymlinkPreservingWorkDir() computes
the git working directory path while preserving symlinks from
the original user path.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/21092

common/git/kicad_git_common.cpp

@@ -46,6 +46,7 @@ KIGIT_COMMON::KIGIT_COMMON( git_repository* aRepo ) :
 KIGIT_COMMON::KIGIT_COMMON( const KIGIT_COMMON& aOther ) :
         // Initialize base class and member variables
         m_repo( aOther.m_repo ),
+        m_projectDir( aOther.m_projectDir ),
         m_connType( aOther.m_connType ),
         m_remote( aOther.m_remote ),
         m_hostname( aOther.m_hostname ),
@@ -69,6 +70,24 @@ git_repository* KIGIT_COMMON::GetRepo() const
     return m_repo;
 }
 
+
+wxString KIGIT_COMMON::GetProjectDir() const
+{
+    if( !m_projectDir.IsEmpty() )
+        return m_projectDir;
+
+    if( m_repo )
+    {
+        const char* workdir = git_repository_workdir( m_repo );
+
+        if( workdir )
+            return wxString( workdir );
+    }
+
+    return wxEmptyString;
+}
+
+
 wxString KIGIT_COMMON::GetCurrentBranchName() const
 {
     wxCHECK( m_repo, wxEmptyString );