I'm very sorry, I indeed forgot the `diff.renames=copies`.

The following script can reproduce the bug even with a blank config:

---------------------

# Make a test repo
git init testrepo
cd testrepo
git config user.name A
git config user.email B
git config diff.renames copies

# Add a file called orig
echo 'a' > orig
git add orig
git commit -m'orig'

# Copy orig in new and modify orig
cp orig new
echo 'b' > orig

# add -N and then commit trigger the bug
git add -N new
git commit

# Cleanup
cd ..
rm -rf testrepo

Il 26/09/18 22:56, Ævar Arnfjörð Bjarmason ha scritto:
> 
> On Wed, Sep 26 2018, Andrea Stacchiotti wrote:
> 
>> Dear maintainer(s),
>>
>> the following script, when executed with git 2.19 triggers the bug in
>> the subject line.
>> The problem seems to be the interaction between add -N and rename detection.
>>
>> The git binary used is the one currently packaged in Debian unstable.
>>
>> I have searched the list for the bug text and have found nothing,
>> apologies if the bug is already known.
>>
>> System information, script content and script output follow.
>>
>> Andrea Stacchiotti
>>
>> --------------------------
>>
>> andreas@trelitri:/tmp$ uname -a
>> Linux trelitri 4.17.0-3-amd64 #1 SMP Debian 4.17.17-1 (2018-08-18)
>> x86_64 GNU/Linux
>> andreas@trelitri:/tmp$ git --version
>> git version 2.19.0
>>
>> andreas@trelitri:/tmp$ cat bugscript.sh
>> # Make a test repo
>> git init testrepo
>> cd testrepo
>> git config user.name A
>> git config user.email B
>>
>> # Add a file called orig
>> echo 'a' > orig
>> git add orig
>> git commit -m'orig'
>>
>> # Copy orig in new and modify orig
>> cp orig new
>> echo 'b' > orig
>>
>> # add -N and then commit trigger the bug
>> git add -N new
>> git commit
>>
>> # Cleanup
>> cd ..
>> rm -rf testrepo
>>
>> andreas@trelitri:/tmp$ LANG=C ./bugscript.sh
>> Initialized empty Git repository in /tmp/testrepo/.git/
>> [master (root-commit) 5dedf30] orig
>>  1 file changed, 0 insertions(+), 0 deletions(-)
>>  create mode 100644 orig
>> BUG: wt-status.c:476: multiple renames on the same target? how?
>> ./bugscript.sh: line 18: 22762 Aborted                 git commit
> 
> I can't reproduce this on Debian AMD64 either 2.19.0 in unstable, or
> 2.19.0.605.g01d371f741 in experimental. I tried moving my ~/.gitconfig
> out of the way, do you have some config options there that might be
> contributing to this?
>