Re: git-diff: --ignore-matching-lines has no effect on the output when --name-only is used

From: Lidong Yan <yldhome2d2@gmail.com>
Date: Jul 25, 2025, 06:46 UTC
Message-ID: <6A35A7CF-966B-4EC7-B575-86E6CCB68D03@gmail.com>
In-Reply-To: <87v7ngstc8.fsf@arnes.space>

hi@arnes.space writes:

Show 8 quoted lines

> 
>> it does not make sense for the answer to be different depending on the
>> presense of -w or --ignore-matching options.
> 
> does it really not? i thought of `--name-only` as changing the
> formatting of the output, as doing something similar to this:
> 
> git diff --no-ext-diff ... | grep -P "^(---|\+\+\+)" | cut -d/ -f2- | uniq

Git computes a SHA value for each file, so when using --name-only to check which files have changed, it only needs to compare the SHA values. There's no need to generate and then filter the full diff content.

Of course, the implementation of git diff is more complex, but I hope you can roughly understand that --name-only usually doesn't need the actual diff content.

Thanks, Lidong