GIT commit messages are generally comprised of three sections: a short summary, a longer explanation, and links to references. Starting with this structure forces you to answer why the change is necessary before outlining the changes that you have made.

• The summary should be no longer than 50 characters
• The summary should be tagged with what type of commit it is. For example, "[feat] Added a new feature" or "[fix] Fixed a bug".
• Each line of the explanation should wrap at 72 characters
• If a commit fixes an issue, it should be denoted with Fixes: {url}
• If a commit references another commit, outside source, etc, it should be denoted with Refs: {url}

The summary is required but the longer explanation and refs may not always be necessary or apply to the situation at hand.

Template

You can tell GIT to use a template for commit messages with this structure. This is done by setting commit.template in ~/.gitconfig:

[commit]
  template = ~/.gitmessage

Then create ~/.gitmessage with the following:

#-----------------------50-----------------------|
#Summary (50 characters)

#----------------------------------72----------------------------------|
#Explanation (wrap around 72 characters (80 - short indent on either side))

#----------------------------------72----------------------------------|

#----------------------------------72----------------------------------|
#Refs:
#Fixes:
#----------------------------------72----------------------------------|
# Type can be
#    feat     (new feature)
#    fix      (bug fix)
#    refactor (refactoring production code)
#    style    (formatting, missing semi colons, etc; no code change)
#    docs     (changes to documentation)
#    test     (adding or refactoring tests; no production code change)