find branch name during git rebase

Question

What?

Is there a way to find the name of the branch-being-rebased during an interactive rebase, that is better than parsing .git/rebase-merge/head-name?

Details

Normally I use git rev-parse --abbrev-ref HEAD to get the branch name. But during a rebase the branch is in a detached head state and rev-parse returns HEAD.

So now I'm parsing the .git/rebase-merge/head-name file if it exists to pull out the branch name. Is there a method (porcelain or otherwise) to get this data?

Usage:

git checkout "the_branch_name_I_want"
git rebase -i "some_other_branch_sha_etc"
# mark commit for edit ...
git magic-command # I'd like to get back "the_branch_name_I_want"
git rebase --continue

Why?

Why do I want to do this?

I store metadata about the branch and fetch it in my commit-msg hook to append to my commit message. I want this to work when rewording or editing my commit messages during interactive rebase.

Code:

branch=$(git rev-parse --abbrev-ref HEAD 2>/dev/null)
if [ "$?" -ne 0 ]; then
    echo "not in a git repo!"
    exit 2
fi
if [ "$branch" = "HEAD" ]; then
    # check if we are in a rebase
    head_name_file="$(git rev-parse --git-dir)/rebase-merge/head-name"
    if [ -f "${head_name_file}" ]; then
        branch=$(cut -f3- -d/ $head_name_file)
    else
        # ignore DETACHED HEAD state.
        exit 1
    fi
fi
## do something with branch

Answer 1

Although git branch --list shows a branch name (see this answer for the details), it is not useful during the scripting as you need to parse the output.

I use the following function to get a branch name (based on head-name file):

rebasing-branch() {
    for location in rebase-merge rebase-apply; do
        path=$(git rev-parse --git-path ${location})
        if test -d ${path}; then
            revision=$(<${path}/head-name)
            echo ${revision##refs/heads/}
            return 0
        fi
    done
}

It shows the branch name during either regular or interactive rebase.