http://pablo2httpff4vogufavlmbxw4jkgb3amnywex2xdnchpztkdu2luead.onion/software.html
In its hooks, fugitive uses only standard UNIX® tools that are included in the GNU core-utils package, plus sh as script interpreter (yes, not even Bash, just plain sh).
That's it. For the same reason this is awesome, it can be extremely slow:
there are no data structures in sh, which means that it uses temporary files even for lists, thus performing a lot of I/O;
and also starting a new process is necessary for each command of the script.