By FTP I mean: http://ftp.gnome.org/pub/GNOME/sources/glibmm/ (version 2.52 and 2.54). As for git, I had in mind obtaining zip file from https://git.gnome.org/browse/glibmm/ .
Now I see, that there are some files with .hg extension in git sources. Should I do something before opening solution file in Visual Studio?