Question:Why configure file does not exist on git repository?

[川原智和]

My name is tmn3164. I am a beginner of gnu softwares.

I am now trying to build autoconf from scratch on macOS.
I get source git repo ().

Your manual tell me to do first "./configure".
However, there is no configure file, but configure.ac .
Ofcource, autoconf is not installed in my machine and cannot run "autoconf"
command.

Why configure file does not exist on git repository?
Why your repo  force me to use autoconf to build autoconf ?
I don't need  advices "Use homebrew" or "get autoconf.zip".
How can I build autoconf from scratch with ONLY source code  on git
repository ?

thak you.