Issue with git's handling of the prepare-commit-msg hook

I believe there's an issue with git's very own mechanism of triggering the prepare-commit-msg hook.

According to the documentation, said hook is supposed to receive squash as source of commit message (i.e. its second argument) when a "SQUASH_MSG" file is present, i.e. when a squash is currently ongoing.

This repository serves to show that this isn't the case during an interactive rebase. Instead, git passes message to the prepare-commit-msg hook.

From the documentation of the prepare-commit-msg hook[1]:

It takes one to three parameters. The first is the name of the file that contains the commit log message. The second is the source of the commit message, and can be: message (if a -m or -F option was given); template (if a -t option was given or the configuration option commit.template is set); merge (if the commit is a merge or a .git/MERGE_MSG file exists); squash (if a .git/SQUASH_MSG file exists); or commit, followed by a commit SHA-1 (if a -c, -C or --amend option was given).

Usage

1. Copy or link prepare-commit-msg to this repositories' ./git/hooks/prepare-commit-msg
2. Run run-demonstration.sh and follow the on-screen directions.

Sources

1 - https://git-scm.com/docs/githooks#_prepare_commit_msg