Normally, you don't modify source files when working with Patcher. However, ChangeLog files need update and saving in automatic mode. Patcher provides two hooks for plugging in additional processing on ChangeLog files.

• :link-change-log-hook This hook is run every time Patcher “links” a ChangeLog file to a project. Linking a ChangeLog file in this context means figuring out that it is involved in the current patch. Every function in this hook will be given the ChangeLog file name (relative to the project's directory) as argument. Also, it is guaranteed that when this hook is run, the current directory (in whatever the current buffer is) is set to the project's directory.
• :after-save-change-log-hook This hook is run every time you save a ChangeLog file. The functions in this hook are executed in the ChangeLog's buffer. To be honest with you, I didn't invent anything here, and I must confess that this is not a real hook. Instead, what you specify in this project option is simply added to the ChangeLog's local after-save-hook.

Now you're wondering what you could possibly use these two options for (apart from ringing the terminal bell I mean), and you're right. In fact, their existence comes from my desire to support Git projects by index.

If you look at patcher-built-in-themes, you will find two themes for Git (along with their their whitespace-cleaning counterpart): git and git-index. The git-index one will only work on what's in the Git staging area. This is cool as long as ChangeLog files are written by hand see Manual ChangeLogs. However, in automatic mode, we need a way to add them to the index once the skeletons are filled in. This is done by another built-in theme that you must add explicitly to your project, called git-index-automatic-change-logs. This theme uses the two options described above to automatically add ChangeLog entries to the staging area.