Re: [PATCH 2/3] merge-recursive: make empty tree a known object

From: Linus Torvalds <torvalds@osdl.org>
Date: Dec 10, 2006, 18:37 UTC
Message-ID: <Pine.LNX.4.64.0612101030390.12500@woody.osdl.org>
In-Reply-To: <Pine.LNX.4.63.0612100055390.28348@wbgn013.biozentrum.uni-wuerzburg.de>

On Sun, 10 Dec 2006, Johannes Schindelin wrote:

> 
> To use it in diff_tree_sha1(), a tree has to be hashed in the
> global object collection. This actually moves the empty tree (if
> it is needed) into the global object hash.

I think you should do this more generically.

If we create this kind of "default fake object" that we know about whether the object _really_ exists or not (and I agree it makes sense for the empty tree), we should probably use it for "diff_root_tree_sha1()" too, rather than the special case we have now.

In other words, right now we have that very special "diff_root_tree_sha1()" function, but if you create a generic fake "empty tree" SHA1 that git knows about implicitly, we could entirely replace it with just using

	diff_tree_sha1(EMPTY_TREE_SHA1, tree, base, opt);

instead, and get rid of that special case code (which is efficient, but we don't really _need_ the efficiency).

So you could make "read_sha1_file()" just have a special case for known objects at the end. If the pack entry fails, the loose file case fails, then rather than returning NULL at the end, you could have a list of known fixed objects..

Hmm?