Is there a way to 'script' a git commit - only accepting some diffs?

Question

I have applied some static code analysis - and transformed all Java package level fields into protected. This is mostly correct, as I forgot to set the access modifier explicitly, and protected is generally what I was after in those cases.

Unfortunately, the refactoring I applied was the IntelliJ weaken access modifiers on, and it also changes lots of public -> protected, on constructors and so on.

So once I have a diff with statements like this in it:

-int myField;
+protected int myField;

and

-public MyConstructor()
+protected MyConstructor()

Is there a way to write a script, that runs during the commit, and only lets the first example above, but no the second? I can figure out the script, and I am just not sure how to run it - is it a pre-commit hook?

If its a pre-commit hook, how do you examine the diff in such a script and accept/reject it based on greping it for some string?

Answer 1

Yep you can do it using smudge/filters

There are several ways to do it.

git hooks

git hooks is a script that run in a different phases of the git life-cycle.
In the proper hook file check the for the file/content that you need and do whatever you need with it.

The hook will run on your files and will check the syntax.

Smudge/clean

Basically, smudge is equivalent to run this code whenever you check anything out
and clean is equivalent to run this code whenever you check anything in.

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