Re: [PATCH 2/3 v3] Use an external program to implement fetching with curl

Hi,

On Wed, 5 Aug 2009, Sverre Rabbelier wrote:

On Wed, Aug 5, 2009 at 08:45, Daniel Barkalow[off-list ref] 
wrote:

quoted

Someday, I want to have a diff output format that makes these things 
clear somehow. I think it would be not-too-hard to get the diff code 
to determine that an addition matches or almost matches a deletion (or 
some unchanged code), and provide library access to this information, 
but representing it to humans (and getting patch to still work) is 
hard.

I started on this a while ago (as part of some post-GSoC git-stats 
work), but I had a hard time finding a good rule to determine whether an 
added hunk is similar enough to a deleted hunk elsewhere. Perhaps a 
variant of Levenshtein can be used to determine how different two hunks 
are; I tried diffing the two hunks and then looking at the ration 
between the size of the diff and the size of the original hunk, but as 
said that didn't really work out.

I think that there are two complications:

- how to present it in a format that helps the human to understand, yet is 
  well-defined enough to be used as a machine-readable edit script (I 
  really do not think that it can be well-designed if it only fulfills one 
  of the two purposes).  I could imagine something like this:

	diff --git a/remote-curl.c b/remote-curl.c
	partial copy from transport.c +394,130
		#ifndef NO_CURL
		static int curl_transport_push(struct transport *transport, int refspec_nr, const char **refspec, int flags)
		{
		[...]
		}

		#endif
	@@ -1,4 +1,6
	+#include "cache.h"
	+#include "transport.h"
	+#include "refs.h"
	+
	 #ifndef NO_CURL
	 static int curl_transport_push(struct transport *transport, int refspec_nr, const char **refspec, int flags)

- how to determine efficiently where to spend a lot of time to determine 
  what could be similar enough.

For example, the diff would still look pretty unreadable if you determined 
that there was a code move which involved a reindentation, so I am not at 
all sure if it is worth to try hard to detect that that was a move after 
all.

Ciao,
Dscho