Re: [PATCH] import-tars: Use the "Link indicator" to identify directories

From: Junio C Hamano <junkio@cox.net>
Date: May 16, 2007, 18:24 UTC
Message-ID: <7vsl9weie0.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <Pine.LNX.4.64.0705161659530.6410@racer.site>

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> Earlier, we used the mode to determine if a name was associated with
> a directory. This fails, since some tar programs do not set the mode
> correctly. However, the link indicator _has_ to be set correctly.

Show 6 quoted lines

> 	The problem is -- again -- that a directory is overwritten, since 
> 	it is not recognized as a directory. Earlier, I tried to use the 
> 	trailing "/" for that. Which fails with your example.
>
> 	I actually took the time to research in Wikipedia what should be 
> 	the correct way to find out if the current item is a directory...

This matches my reading of GNU tar as well. The patch would not break a correctly made tar archive, would fix importing archives created by a broken tar that does not do mode right (but uses the correct typeflag), _and_ would _break_ archives created by tar that is broken in a different way, sets the mode right but uses a wrong typeflag.

I do not know which breakages are more common, and this one being in contrib/ I do not think it really matters in practice, but as a principle, I think we should try to adhere to the same "no regression" policy the kernel folks try to adhere to. If something used to work, even if its was by accident or a bug, we had better have a pretty good reason to break it by a change that fixes things for other people, _even_ when that other people outnumber the people who are affected by the regression.

I'd first ask GNU tar maintainer if he knows of existing implementations of tar that are broken in the latter sense (iow, sets modes correctly but typeflag incorrectly), as the tarball extraction codepath would have the exact same issue.