Since it starts and ends in G, I'd assume G major:
G - Cmaj7 - F#m7 - G#m7 - Em7 - Cmaj7 - D/F# - G or
I - IV - (vii#5)- (bii) - vi - IV - V - I or
1 - 4 - 7#5m7? - b2m7? - 6 - 4 - 5 - 1.
OK so, the F#m7 doesn't seem all too strange. It would be like seeing a Bm or D in the key of C. Maybe Lydian or Dorian or like in the beginning of "Yesterday" for instance. But that 4th chord the G#m7(flat 2 thingy) is confusing me pretty bad.
Is this whole thing modal or a key change to E(without using the E major) or what? It's not out of the "borrowed" chords (from the 3 to left group on circle of 5ths) from parallel minor key. It is from the 3 to the right group on the circle (where you'd find secondary dominants) except its minor 7. I doubt that can be called secondary dominant.
Do the minors or minor 7ths from that group have a name? How might this be analyzed? Btw the song is "Only Elliot" by Tommy Emmanuel.