Re: [PATCH 4/4] Add 'filter' attribute and external filter driver definition.

From: Junio C Hamano <junkio@cox.net>
Date: Apr 22, 2007, 06:33 UTC
Message-ID: <7v4pn8rk8t.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <Pine.LNX.4.63.0704211821560.5655@qynat.qvtvafvgr.pbz>

David Lang <david.lang@digitalinsight.com> writes:

> 1. it would be useful in many cases for the filter program to know
> what file it's working on (and probably some other things), so there
> are probably some command-line arguments that should be able to be
> passed to the filter.

I can see that you missed the class when Linus talked about how messy things would get once you allow the conversion to be stateful. I was in the class and remembered it ;-)

Although I initially considered interpolating "%P" with pathname, I ended up deciding against it, to discourage people from abusing the filter for stateful conversion that changes the results depending on time, pathname, commit, branch and stuff.

Show 5 quoted lines

> 2. should this be done as a modification of the in-memory buffer (s
> this patch does it?) or should it be done at the time of the
> read/write, makeing the filter be responsible for actually doing the
> disk I/O, which would give it the benifit of being able to do things
> like set permissions and other things ...

The conversion is not about overriding the mode bits recorded in tree objects, nor making git as a replacement for build procedure.

> 3. why specify seperate clean/smudge programs instead of just one
> script with a read/write parameter?

I think the most common two ways have clean as a cleaner and smudge as a no-op (similar to crlf=input conversion), or clean and smudge are inverse operations (similar to crlf=true conversion. I do not see a sane case where clean and smudge are the same, unless you are thinking about the toy demonstration test piece I added to t0021 which uses rot13 as both clean and smudge filters.