Git: Show error when pull fails due to unstaged changes

When git pull fails due to unstaged changes in the working directory,
show an informative error message instead of silently failing.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/20363

(cherry picked from commit 0b116673ab)

common/git/git_pull_handler.cpp

@@ -378,6 +378,14 @@ PullResult GIT_PULL_HANDLER::handleFastForward()
 PullResult GIT_PULL_HANDLER::handleMerge( const git_annotated_commit** aMergeHeads,
                                           size_t                       aMergeHeadsCount )
 {
+    if( hasUnstagedChanges( GetRepo() ) )
+    {
+        AddErrorString(
+                _( "Cannot merge: you have unstaged changes. "
+                   "Please commit or stash them before pulling." ) );
+        return PullResult::DirtyWorkdir;
+    }
+
     git_merge_options merge_opts;
     git_merge_options_init( &merge_opts, GIT_MERGE_OPTIONS_VERSION );
 
@@ -481,6 +489,14 @@ PullResult GIT_PULL_HANDLER::handleMerge( const git_annotated_commit** aMergeHea
 
 PullResult GIT_PULL_HANDLER::handleRebase( const git_annotated_commit** aMergeHeads, size_t aMergeHeadsCount )
 {
+    if( hasUnstagedChanges( GetRepo() ) )
+    {
+        AddErrorString(
+                _( "Cannot rebase: you have unstaged changes. "
+                   "Please commit or stash them before pulling." ) );
+        return PullResult::DirtyWorkdir;
+    }
+
     // Get the current branch reference
     git_reference* head_ref = nullptr;
 
@@ -563,6 +579,40 @@ PullResult GIT_PULL_HANDLER::handleRebase( const git_annotated_commit** aMergeHe
 }
 
 
+bool GIT_PULL_HANDLER::hasUnstagedChanges( git_repository* aRepo )
+{
+    if( !aRepo )
+        return false;
+
+    git_status_options opts;
+    git_status_init_options( &opts, GIT_STATUS_OPTIONS_VERSION );
+
+    opts.show = GIT_STATUS_SHOW_WORKDIR_ONLY;
+    opts.flags = GIT_STATUS_OPT_INCLUDE_UNTRACKED;
+
+    git_status_list* status_list = nullptr;
+
+    if( git_status_list_new( &status_list, aRepo, &opts ) != GIT_OK )
+    {
+        wxLogTrace( traceGit, "Failed to get status list: %s", KIGIT_COMMON::GetLastGitError() );
+        return false;
+    }
+
+    KIGIT::GitStatusListPtr status_list_ptr( status_list );
+    size_t count = git_status_list_entrycount( status_list );
+
+    for( size_t ii = 0; ii < count; ++ii )
+    {
+        const git_status_entry* entry = git_status_byindex( status_list, ii );
+
+        if( entry->status & ( GIT_STATUS_WT_MODIFIED | GIT_STATUS_WT_DELETED | GIT_STATUS_WT_TYPECHANGE ) )
+            return true;
+    }
+
+    return false;
+}
+
+
 void GIT_PULL_HANDLER::UpdateProgress( int aCurrent, int aTotal, const wxString& aMessage )
 {