Personally I also suggest using an external solution (like git), but I also think it would be great for osticket to detect newly released Versions and offer an (auto-)upgrade message and option to upgrade to the latest version.
Some additional suggestion:
Right after 1.9.0 release there were some issues (css typo, etc.) fixed and you @[deleted] / @[deleted] updated the downloadable zip file to include the fix. There Version (1.9.0) thou, did not change. So in case of not looking into the forum here or on github I would never notice that (until the next release 1.9.1, 2.0, etc.) and re-download the package. Would be great if such "quickfix releases" would be published e.g. as 1.9.0-(quick)fix-1 or 1.9.0a or 1.9.0.1 or ... whatever you want to call it.