Re: [1/5] Parsing code in revision.h

From: Petr Baudis <pasky@ucw.cz>
Date: Apr 17, 2005, 18:30 UTC
Message-ID: <20050417183002.GE1461@pasky.ji.cz>
In-Reply-To: <Pine.LNX.4.58.0504171114020.7211@ppc970.osdl.org>

Dear diary, on Sun, Apr 17, 2005 at 08:18:47PM CEST, I got a letter where Linus Torvalds <torvalds@osdl.org> told me that...

Show 20 quoted lines

> 
> 
> On Sun, 17 Apr 2005, Daniel Barkalow wrote:
> >
> > --- 45f926575d2c44072bfcf2317dbf3f0fbb513a4e/revision.h  (mode:100644 sha1:28d0de3261a61f68e4e0948a25a416a515cd2e83)
> > +++ 37a0b01b85c2999243674d48bfc71cdba0e5518e/revision.h  (mode:100644 sha1:523bde6e14e18bb0ecbded8f83ad4df93fc467ab)
> > @@ -24,6 +24,7 @@
> >  	unsigned int flags;
> >  	unsigned char sha1[20];
> >  	unsigned long date;
> > +	unsigned char tree[20];
> >  	struct parent *parent;
> >  };
> >  
> 
> I think this is really wrong.
> 
> The whole point of "revision.h" is that it's a generic framework for 
> keeping track of relationships between different objects. And those 
> objects are in no way just "commit" objects.

Someone started the avalanche by adding date to the structure. Of course, date is smaller, but it leads people (including me) out of the way.

Perhaps struct commit which will have struct revision (ugh - what about rather struct object?) as a member?

> For example, fsck uses this "struct revision" to create a full free of 
> _all_ the object dependencies, which means that a "struct revision" can be 
> any object at all - it's not in any way limited to commit objects, and 
> there is no "tree" object that is associated with these things at all.

That's some really bad naming then.

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> Besides, why do you want the tree? There's really nothing you can do with 
> the tree to a first approximation - you need to _first_ do the 
> reachability analysis entirely on the commit dependencies, and then when 
> you've selected a set of commits, you can just output those.
> 
> Later phases will indeed look up what the tree is, but that's only after
> you've decided on the commit object. There's no point in looking up (or
> even trying to just remember) _all_ the tree objects.

The goal was to have a commit record parser which would spit out this structure containing all the relevant info, but I can agree that wasting memory with it makes no sense. Perhaps it could take a possibly-NULL buffer pointer where it would drop the tree ID, Daniel?

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
C++: an octopus made by nailing extra legs onto a dog. -- Steve Taylor