I pity anyone who tries to review the entire changeset :)
This is why I'd suggest reviewing it as if it was a single commit
"Take over upstream ctags and apply Geany changes on top"
which is how it will appear when you take meld and compare upstream ctags/main with geany-ctags/main. The diff is just a few hundreds LOCs.
I did it this painful way myself to make sure nothing what Geany needs was lost on the way.
The only changes worth reviewing in greater detail are those that affect parsers (mostly cork introduction), lcpp.c changes and that's about it.