fetch: try use gix to fetch package src

[eatradish]

But when acbs-build xxx is used again, there is a problem:

Error: './.git/objects' wasn't a directory

However, when I do the same steps manually, the problem does not reproduce:

gix clone --bare https://github.com/AOSC-Dev/oma oma-1
cd oma-1
gix fetch origin +refs/heads/*:refs/heads/*

[what-the-diff]

PR Summary

• Added New Function for Managing Git Repositories
  A new functionality has been introduced that significantly improves how we interact with Git repositories. Previously, it had to be manually checked whether the repository exists or not. Now, this process is automated. The new function, git_fetch, determines if a repository exists, if not, it initially sets it up by cloning it. In case the repository already exists, this function helps keep it up-to-date by fetching the latest changes.

• Incorporated gix_fetch for Enhanced Efficiency
  In situations where gix is available, another function called gix_fetch is utilized within the git_fetch sequence for added efficiency. This means, depending on the circumstances and tools available, the system can choose the most effective method to fetch repositories, optimizing performance.