How to show the content of a release with Git

Should we maintain a change log file? Or simply use the Git messages? With Git log this is as easy as:

$ git log --pretty=oneline --abbrev-commit 1234...5678

This command will print the first line of the commit messages of commit [1234] to [5678] (excluding [5678]).

Based on the answer to How to output git log with the first line only?