bug report: "git pack-redundant --all" crash in minimize()

["Daniel C. Klauer" <daniel.c.klauer@web.de>]

Hello,

I'm getting the following crash from "git pack-redundant --all" (output
from valgrind):

==14070== Invalid read of size 8
==14070==    at 0x18F165: minimize (pack-redundant.c:399)
==14070==    by 0x18F165: cmd_pack_redundant (pack-redundant.c:622)
==14070==    by 0x1242D3: run_builtin (git.c:444)
==14070==    by 0x1242D3: handle_builtin (git.c:674)
==14070==    by 0x125393: run_argv (git.c:741)
==14070==    by 0x125393: cmd_main (git.c:872)
==14070==    by 0x123E7D: main (common-main.c:52)
==14070==  Address 0x10 is not stack'd, malloc'd or (recently) free'd

Commands to reproduce:

mkdir new
cd new
git init
touch foo.txt
git add foo.txt
git commit -m "first commit"
git gc
git pack-redundant --all

The same happens with Ubuntu's git 2.25.1 as well as manually compiled
git 2.30.0.rc0 from current master.

The reason this showed up is that Yocto's build tool, bitbake, sometimes
invokes this git command on some of the repositories it downloaded. This
issue was apparently also reported here:
https://bugzilla.redhat.com/show_bug.cgi?id=1803506

Kind Regards,
Daniel