There's a bunch of different utilities in there. Each has it's own main() function, and they're compiled into a bunch of binaries.

There are multiple main() functions because there are multiple programs! Check out https://github.com/git/git/commit/e83c5163316f89bfbde7d9ab23...

Look at the makefile, it just has a command line program for each basic operation.

Could just be initializers for different modules maybe?