How can I change the default comments in the git commit message?

Is it possible to modify the commented part of the default git commit message? I want to add a bit more 'context' information for my users.

# Please enter the commit message for your changes.
# (Comment lines starting with '#' will not be included)
# Explicit paths specified without -i nor -o; assuming --only paths...
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#       modified:   test.txt
#

There is commit.template configuration variable, which according to git-config(1) manpage:

> Specify a file to use as the template for new commit messages. "~/" is expanded to the value of $HOME and "~user/" to the specified user's home directory.

You can put it in per-repository (.git/config), user's (~/.gitconfig) and system (/etc/gitconfig) configuration file(s).

You can use http://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks">git hooks for that. Before the person who wants to commit the changes is shown the commit message, the prepare-commit-msg script is run.

You can find an example prepare-commit-msg script in .git/hooks.

To edit the default message create a new file called prepare-commit-msg in the .git/hooks folder. You can edit the commit message by using a script like this:

#!/bin/sh
echo "#Some more info...." >> $1

The $1 variable stores the file path to the commit message file.

Here is a python git-hook to clean up the default message. Hook name: prepare-commit-msg.

#!/usr/bin/env python
import sys
commit_msg_file_path = sys.argv[1]
with open(commit_msg_file_path, 'a') as file:
    file.write('')

You can simply add you text in the file.write() method.

Put something like this in .gitconfig (source):

[commit]
  template = ~/myGitMessage.txt

and in that file content, set your default commit message.