Generate *.devhelp2 index files, the Devhelp index file format version 1 is deprecated.
When opening Devhelp from the terminal, there is a warning about the Devhelp index file format version 1 being deprecated, when Devhelp finds and reads such index files.
Unfortunately the format version 2 is not really documented, the best way to learn it is to open a *.devhelp2 file generated by GTK-Doc, for example the one for GLib or GTK+ (or a smaller library to have a smaller example).
Generate *.devhelp2 index files, the Devhelp index file format version 1 is deprecated.
When opening Devhelp from the terminal, there is a warning about the Devhelp index file format version 1 being deprecated, when Devhelp finds and reads such index files.
Unfortunately the format version 2 is not really documented, the best way to learn it is to open a *.devhelp2 file generated by GTK-Doc, for example the one for GLib or GTK+ (or a smaller library to have a smaller example).