Built-in rebase fails with 'Unexpected stash response' (MVCE included)

[rcdailey]

I get the following error when doing a rebase with a modified working copy (submodule modified) and with the configuration option rebase.autostash set to true:

$ git rebase --no-fork-point master
09:34:43.229716 exec-cmd.c:236          trace: resolved executable dir: C:/Program Files/Git/mingw64/bin
09:34:43.230216 git.c:415               trace: built-in: git rebase --no-fork-point master
09:34:43.230216 run-command.c:637       trace: run_command: git config --bool rebase.usebuiltin
09:34:43.238724 exec-cmd.c:236          trace: resolved executable dir: C:/Program Files/Git/mingw64/libexec/git-core
09:34:43.239725 git.c:415               trace: built-in: git config --bool rebase.usebuiltin
09:34:43.249230 run-command.c:637       trace: run_command: git stash create autostash
09:34:43.263242 exec-cmd.c:236          trace: resolved executable dir: C:/Program Files/Git/mingw64/libexec/git-core
09:34:43.263742 git.c:415               trace: built-in: git stash create autostash
09:34:43.263742 run-command.c:637       trace: run_command: git config --bool stash.usebuiltin
09:34:43.274250 exec-cmd.c:236          trace: resolved executable dir: C:/Program Files/Git/mingw64/libexec/git-core
09:34:43.275251 git.c:415               trace: built-in: git config --bool stash.usebuiltin
fatal: Unexpected stash response: ''

Here is the MVCE (simple bash script you can run):

#!/usr/bin/env bash
set -o xtrace

git init mvce_stash_failure
pushd mvce_stash_failure
git config rebase.autostash true

# Add stuff to master
git init thesubmodule
pushd thesubmodule
echo submodule > submodulefile1
git add submodulefile1
git commit -m 'submodulefile1 added'
popd

git add thesubmodule
git commit -m 'added submodule'

echo value > file1
git add file1
git commit -m 'file1 added'

echo value > file2
git add file2
git commit -m 'file2 added'

# Add stuff to a feature branch
git checkout -b topic1 @^
echo value2 > file2
git add file2
git commit -m 'file2 added'

pushd thesubmodule
echo submodule > submodulefile2
git add submodulefile2
git commit -m 'submodulefile2 added'
popd

# This fails with: fatal: Unexpected stash response: ''
GIT_TRACE=1 git rebase --no-fork-point master

popd
rm -rf mvce_stash_failure

Using Git for Windows v2.19.1 with experimental built-in stash & rebase enabled via installer options.

[t-b]

@rcdailey yeep, same as #1820.

Workaround:

git submodule update --checkout --force