On Sat, Sep 01 2018, Luc Van Oostenryck wrote:
> Hi,
>
> I've just had a scary error:
> error: index uses $?+? extension, which we do not understand
> fatal: index file corrupt
>
> Things were quickly recovered by deleting the index but it clearly
> looks to a but to me.
>
> Here are the steps to reproduce it:
> $ git clone git://github.com/lucvoo/sparse-dev.git <somedir>
> $ cd <somedir>
> $ git co index-corruption
> $ git rm -r validation/ Documentation/
> $ git commit -m <some message> -p
> $ git status
> error: index uses $?+? extension, which we do not understand
> fatal: index file corrupt
>
>
> The 'extension' pattern '$?+?', can vary a bit, sometimes
> it's just '????', but always seems 4 chars.
> If the commit command doesn't use the '-p' flag, there is no
> problem. The repository itself is not corrupted, it's only
> the index. It happends with git 2.18.0 and 2.17.0
Yeah this is a bug, I didn't dig much but testing with this script down
to 2.8.0:
#!/bin/sh
cd ~/g/git
make -j $(parallel --number-of-cores) USE_LIBPCRE2=YesPlease CFLAGS="-O0 -g -ggdb3" DEVELOPER=1 DEVOPTS=no-error NO_OPENSSL=Y all
(
rm -rf /tmp/x;
~/g/git/git --exec-path=/home/avar/g/git clone git://github.com/lucvoo/sparse-dev.git /tmp/x &&
cd /tmp/x &&
~/g/git/git --exec-path=/home/avar/g/git checkout index-corruption &&
~/g/git/git --exec-path=/home/avar/g/git rm -r validation/ Documentation/ &&
~/g/git/git --exec-path=/home/avar/g/git commit -p
)
~/g/git/git --exec-path=/home/avar/g/git -C /tmp/x status
if ~/g/git/git --exec-path=/home/avar/g/git -C /tmp/x status
then
exit 0
else
exit 1
fi
I found that the first bad commit was: 680ee550d7 ("commit: skip
discarding the index if there is no pre-commit hook", 2017-08-14)
Now, note the two invocations of "status" in my script. Before we'd
already been complaining about a bad index, but after that commit is the
first time we started getting a persistent error, and indeed even
reverting it now on top of master makes the error non-persistent.
So not a fix, but a strong signal to see where we should start
looking. I.e. the index file handling around discard_cache() &
"interactive" in commit.c is likely what's broken.
