This branch activates input source switch using "grp:" accelerator from xkb-options. It allows to use accelerator + key combos (Ctrl+Shift+T in Terminal) while input source can be switched with a modifiers only accelerator (Ctrl+Shift). It's the same thing Gnome Shell does actually. Works for me when switching between Russian and English layouts, may need more testing. Plus I'm not sure what place this code belongs to, so I just made a new file.