Memory leak with sparse-checkout

[Calbabreaker <calbabreaker@gmail.com>]

What did you do before the bug happened? (Steps to reproduce your issue)

This was ran:

git clone https://github.com/Calbabreaker/piano --sparse
cd piano
git sparse-checkout add any_text
git checkout deploy-frontend
git sparse-checkout init --cone
git sparse-checkout add any_text

Basically clone any repository with --sparse, add anything to
sparse-checkout list
then checkout to another branch, init the sparse-checkout with --cone and add
anything to it again.

What did you expect to happen? (Expected behavior)

Nothing at all except for the sparse-checkout list to be updated.

What happened instead? (Actual behavior)

A massive memory leak using all the RAM with one of the cpu cores
being at 100% usage.

[System Info]
git version:
git version 2.33.0
cpu: x86_64
no commit associated with this build
sizeof-long: 8
sizeof-size_t: 8
shell-path: /bin/sh
uname: Linux 5.10.63-1-MANJARO #1 SMP PREEMPT Wed Sep 8 14:13:59 UTC 2021 x86_64
compiler info: gnuc: 11.1
libc info: glibc: 2.33
$SHELL (typically, interactive shell): /usr/bin/zsh