add "Duplicate layer in QGIS" option in Data Views context menu

[Andreas Janz]

Because of #861 we lose layer styling, when drag&drop a layer to QGIS.

Keeping the style is critical in case of custom raster renderer that can’t be restored in QGIS.

Directly adding a cloned layer to QgsProject.instance() should solve this problem.

[Andreas Janz]

Keeping the style is critical in case of custom raster renderer that can’t be restored in QGIS.

Actually, it isn’t that critical, because the tools that define the custom renderer can also manage layers owned by QGIS. After resolving #1017 we wouldn’t really need this option.

But it’s good to have it anyways.

[Andreas Janz]

Done

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[Andreas Janz]

resolves #1016

→ <<cset dd74bcf3c5ff>>