Re: teach git diff -v/--invert-match?

From: Brian Ericson <bme@visi.com>
Date: Aug 22, 2008, 21:29 UTC
Message-ID: <48AF2FBB.2080401@visi.com>
In-Reply-To: <20080822193947.GA31322@coredump.intra.peff.net>

I was just working on a reply to my own email as I realized it was only dumb-luck that converted 1200 noisy changes into a couple of dozen. "-S" matches only the string itself, not the line the string resides on. So, -Sxyz will match if "xyz" itself was added or deleted in the diff (if "xyz" is on a line that's changed but did not itself change, it won't match). Funny that I actually knew this -- I use it to look for System.out.println additions among other things.

Interestingly, if I wanted to know if an import changed (on top of knowing if imports were added or deleted), eg: -import foo; +import bar;

I couldn't tell you how to do it. The string "import" didn't change. I'd've guessed that "-S'import.*;' --pickaxe-regex" would have been sufficient, but that doesn't work.

Jeff King wrote:

Show 9 quoted lines

> On Fri, Aug 22, 2008 at 09:51:16AM -0500, Brian Ericson wrote:
>
>   
>> I'm wondering what it would take to teach git diff to invert the -S  
>> string (like git grep).
>>     
>
> I think you would have to figure out the desired semantics first.
>

I think mostly what I want is a happy marriage between git diff & git grep so that if the changed lines matched (or didn't match) the file would show up (or not). I'd like to grep added and removed lines (the diff itself) for a pattern and either include or exclude the file based on matches.

Show 14 quoted lines

>   
>> I'm finding git diff -S<string> [--pickaxe-regex] to be really useful,  
>> but find I have cases where I want to ignore differences.  For example, I 
>> might not care if the only changes to a Java file, for example, are  
>> related to import statements.  I'd like to be able to do something like  
>> "git diff -S'^import' --pickaxe-regex -v".  I'll admit I can get by with  
>> something like "git diff -S'^[^i]' --pickaxe-regex", but am pining for  
>> -v/--invert-match.
>>     
>
> I would have thought "-v" meant "match any changes which do not have
> this pattern". But you want "match any changes that have any line which
> does not have this pattern."
>

Right. Good summary! It's probably not accurate to use "-S" for my interpretation unless --pickaxe-regex behaved more as I outlined above. It's probably a subtle enough difference

> IOW, mine would not match any changes which used an import statement,
> whereas yours would not match any changes which are _only_ import
> statements.
>

The current behavior seems to work well to answer questions like "has somebody added a System.out.println", I'd like it to be able to ignore or consider files based on line changes that contain a string where the string itself did not change.

Show 8 quoted lines

> -Peff
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