tdf#92623 Handle StartOfContent node for copying bookmarks

For SwDoc::AppendDoc we use the StartOfContent node as the
starting copy node to prevent merging of the first node in
CopyRange and to get a 2nd node needed for CopyRange in case
of single content node documents.

This correctly counts StartOfContent as a non-copy node when
adapting the bookmark ranges for copying.

Change-Id: Ia3ee0328a1be5548f8751aa2240812c4662fb73f
Reviewed-on: https://gerrit.libreoffice.org/20383
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>
diff --git a/sw/source/core/doc/DocumentContentOperationsManager.cxx b/sw/source/core/doc/DocumentContentOperationsManager.cxx
index d1d0254..8fdc824 100644
--- a/sw/source/core/doc/DocumentContentOperationsManager.cxx
+++ b/sw/source/core/doc/DocumentContentOperationsManager.cxx
@@ -124,7 +124,8 @@ namespace
    /*
        The lcl_CopyBookmarks function has to copy bookmarks from the source to the destination nodes
        array. It is called after a call of the _CopyNodes(..) function. But this function does not copy
        every node (at least at the moment: 2/08/2006 ), section start and end nodes will not be copied if the corresponding end/start node is outside the copied pam.
        every node (at least at the moment: 2/08/2006 ), section start and end nodes will not be copied
        if the corresponding end/start node is outside the copied pam.
        The lcl_NonCopyCount function counts the number of these nodes, given the copied pam and a node
        index inside the pam.
        rPam is the original source pam, rLastIdx is the last calculated position, rDelCount the number
@@ -138,6 +139,13 @@ namespace
        sal_uLong nEnd = rPam.End()->nNode.GetIndex();
        if( rLastIdx.GetIndex() < nNewIdx ) // Moving forward?
        {
            // We never copy the StartOfContent node
            // Special handling for SwDoc::AppendDoc
            if( rPam.GetDoc()->GetNodes().GetEndOfExtras().GetIndex() + 1 == nStart )
            {
                ++rDelCount;
                ++rLastIdx;
            }
            do // count "non-copy" nodes
            {
                SwNode& rNode = rLastIdx.GetNode();