Bug Description

PlainClone uses an enormous amount of memory, consuming many times more RAM than a given repo even takes up on disk.

For a large Git repo (private, but can be easily replicated by cloning a public git repo like https://github.com/facebook/react/) that takes up 750MB on disk, go-git consumes nearly 3GB of RAM PlainClone.

go-git Version

HEAD of main 3c570d2

Steps to Reproduce

tmpDir, _ := os.MkdirTemp("", "clone-test")
cloneOptions := &git.CloneOptions{
	URL:        gitURL,
	Progress:   os.Stdout,
}
git.PlainCloneContext(context.Background(), tmpDir, cloneOptions)
os.RemoveAll(tmpDir)

Additional Information

(screenshots are not from the same run)