I can't reproduce "IIRC, I didn't observe this issue with gitlint alone."

Here's my session:

$ git commit
gitlint: checking commit message...
2: B4 Second line is not empty: "asdf"
3: B5 Body message is too short (8<20): "asdfasdf"
-----------------------------------------------
gitlint: Your commit message contains the above violations.
Continue with commit anyways (this keeps the current commit message)? [y(es)/n(no)/e(dit)] n
Commit aborted.
Your commit message: 
-----------------------------------------------
asdf
asdf
asdf

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# On branch master
# Changes to be committed:
#	new file:   foo
#
# Untracked files:
#	venv/
#
-----------------------------------------------
$ git commit

I'm then presented with:

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# On branch master
# Changes to be committed:
#   new file:   foo
#
# Untracked files:
#   venv/
#

There's nothing particularly special about how pre-commit invokes gitlint, as far as I know it should be the same in or out

You're right, it's the default git behavior with the commit-msg hooks which have to take care of the rejected content on their own. Apparently, it takes a backup file and a prepare-commit-msg hook to make the rejected message re-appear. Looks like a new feature request for pre-commit, right?

Could be a neat little feature yeah! Need to be sure it plays nicely if someone defines their own prepare-commit-msg hook and probably mesh with the rest of the framework but definitely sounds like a sharp edge in git that pre-commit could smooth over!

Now that prepare-commit-msg will land in the next pre-commit release, it should be pretty easy to make something like this!

Here's a small demo of this idea, this can probably be cleaned up and turned into a repo: meta hook

.pre-commit-config.yaml

repos:
-   repo: local
    hooks:
    -   id: save-commit-msg
        name: save commit message
        entry: ./bin/save-commit-msg
        verbose: true
        language: script
        stages: [commit-msg]
    -   id: restore-commit-msg
        name: restore commit message
        entry: ./bin/restore-commit-msg
        verbose: true
        language: script
        stages: [prepare-commit-msg]
    -   id: derp
        name: derp
        entry: derp
        language: fail
        stages: [commit-msg]

bin/restore-commit-msg

#!/usr/bin/env python3
import os
import shutil
import sys


def main():
    if os.path.exists('.git/pre-commit-saved-commit-msg'):
        with open(sys.argv[1]) as f:
            lines = [x for x in f if x.strip() if not x.startswith('#')]
        if not lines:
            print('restoring old commit message...')
            shutil.copy('.git/pre-commit-saved-commit-msg', sys.argv[1])


if __name__ == '__main__':
    exit(main())

bin/save-commit-msg

#!/usr/bin/env python3
import shutil
import sys


def main():
    shutil.copy(sys.argv[1], '.git/pre-commit-saved-commit-msg')


if __name__ == '__main__':
    exit(main())

It's a good start, lacking:

• support for gitdir file, e.g. doesn't work in a submodule or a git worktree
• support for git commit --amend, dropping message of the last rejected edit

which I tried to solve, here's what I got so far (using e.g. Play with Docker):

docker run --interactive --tty debian:stable bash

export DEBIAN_FRONTEND=noninteractive
apt update
apt-get dist-upgrade --assume-yes --quiet < /dev/null
apt-get install --assume-yes --quiet curl git python3 python3-setuptools vim < /dev/null
curl https://bootstrap.pypa.io/get-pip.py | python3 - pre-commit

# make Click happy
export LC_ALL=C.UTF-8
export LANG=C.UTF-8

cd
git clone --mirror https://github.com/jorisroovers/gitlint

mkdir gitlint-test
cd gitlint-test
git init
git config user.email "[email protected]"
git config user.name "Your Name"
git commit --allow-empty --message="Initial empty commit"

cat > save-commit-msg <<'EOF'
#!/usr/bin/env sh

cp "${1}" "$(git rev-parse --git-path pre-commit-saved-commit-msg)"
EOF

cat > restore-commit-msg <<'EOF'
#!/usr/bin/env sh

set -e
set -u

msg_file=$(git rev-parse --git-path pre-commit-saved-commit-msg)
[ -r "${msg_file}" ] || exit 0

nr_of_non_empty_lines=$(sed -e '/^#/d' -e '/^[[:space:]]*$/d' "${1}" | wc -l)
if [ "${nr_of_non_empty_lines}" -ne 0 ]
then
    echo "# last commit message:" >> "${1}"
    sed -e '/^#/d' -e 's/^/# /' "${msg_file}" >> "${1}"
    exit 0
fi

echo 'restoring commit message...'
cp "${msg_file}" "${1}"
EOF

chmod +x save-commit-msg restore-commit-msg
git add save-commit-msg restore-commit-msg
git commit --message='Add {save,restore}-commit-msg'

cat > .pre-commit-config.yaml <<EOF
repos:
  - repo: local
    hooks:
    - id: restore-commit-msg
      entry: restore-commit-msg
      language: script
      name: Restore commit message
      stages:
      - prepare-commit-msg
  - repo: ../gitlint.git
    rev: v0.11.0
    hooks:
    - id: gitlint
      stages:
      - commit-msg
  - repo: local
    hooks:
    - id: save-commit-msg
      entry: save-commit-msg
      language: script
      name: Save commit message
      stages:
      - commit-msg
EOF
git add .pre-commit-config.yaml
git commit --message="Add pre-commit config"

for hook_type in prepare-commit-msg commit-msg
do
    pre-commit install --hook-type "${hook_type}"
done
pre-commit install-hooks

touch foo
git add foo
git commit --message=$'This is a good one\n\nMessage body Message body Message body Message body Message body'
git commit --amend --message=$'This is a bad one\nbooooooo'
git commit --amend

The last amend will bring up the last rejected message as a comment in the new one.

One way to bring the commit message back is the suggestion here by @pylipp

git commit --edit --file $(git rev-parse --git-path COMMIT_EDITMSG)