/usr/include/gtksourceview-3.0/gtksourceview/ is in libgtksourceview-3.0-dev 3.22.2-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/gtksourceview-3.0/gtksourceview/completion-providers/
/usr/include/gtksourceview-3.0/gtksourceview/completion-providers/words/
/usr/include/gtksourceview-3.0/gtksourceview/completion-providers/words/gtksourcecompletionwords.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksource.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourceautocleanups.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcebuffer.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcecompletion.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcecompletioncontext.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcecompletioninfo.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcecompletionitem.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcecompletionproposal.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcecompletionprovider.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourceencoding.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcefile.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcefileloader.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcefilesaver.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcegutter.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcegutterrenderer.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcegutterrendererpixbuf.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcegutterrenderertext.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcelanguage.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcelanguagemanager.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcemap.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcemark.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcemarkattributes.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourceprintcompositor.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourceregion.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcesearchcontext.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcesearchsettings.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcestyle.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcestylescheme.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcestyleschemechooser.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcestyleschemechooserbutton.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcestyleschemechooserwidget.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcestyleschememanager.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcetag.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourcetypes.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourceundomanager.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourceutils.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourceversion.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourceview-enumtypes.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourceview-typebuiltins.h
/usr/include/gtksourceview-3.0/gtksourceview/gtksourceview.h