Project list: do not add subdirectory if a project was already added
Submitted by kap..@..ix.org
When opening a file directly from nautilus, its parent directory is added to the projects list, which becomes quickly filled with useless directories.
do not add a directory to the projects list if that directory is contained into another project directory
when opening for the first time a file from nautilus, find if there is a .git/ directory in its ancestor dirs. If any, use that directory as project root.