Using a git pre-commit hook to exclude non-meaningful changes

Question

I've got a large collection of files I want to keep in git. Each of these files has a header that can be automatically updated containing time-stamps and other details about when the file was last exported (they're code files exported from a specific tool)

Since the changes to the header aren't particularly meaningful on their own, I'd like to use a git pre-commit hook to exclude files where there's no change in the actual body of the code. What's the recommended way for me to perform a comparison and discard files where only the first n lines have changes.

Answer 1

A better approach (than trying use a hook) is:

• either to not track those files if they can be regerated
• or track them, but use a content clean filter driver to restore their content if the changes detected are not significant enough.

For the second option, you need a script able to detect if the git diff includes other changes that in the header. If not, the script would perform a git checkout -- afile, in order to restore its content to HEAD (discarding any local changes).

The restoration of the file through that script is automated through a content filter driver, using a .gitattributes declaration.

^{(image from "Customizing Git - Git Attributes" from "Pro Git book"))}

Once you declare that content filer driver in your local config, it will automatically, on git commit, inspect your file for you.
See a complete example in "Best practice - Git + Build automation - Keeping configs separate".