When you want to construct a changelog file from git commit messages you can use git log.
The way to construct such a list of commit messages is to use the git log command like this:
git log --since "DEC 1 2016" --until "FEB 3 2017" --pretty=format:"%s" > git.log.txt

This will only display the text of the commit message.
Other useful format options are :
git log --since "DEC 1 2016" --until "FEB 2 2017" --pretty=format:"%an %ad >> %s"
To get the author name and date.

More info can be found here: git-scm.com/docs/git-log