Re: [PATCH] Do not send "want" lines for complete objects

> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> 
> > Also, git-fetch-pack does not have to ask for descendants of remote refs 
> > which are complete (for now, git-rev-list is told to ignore only the first 
> > parent).
> 
> I should interpret what you said with s/descendant/ancestor/
> applied, I think.  I would like to make sure I understand what
> you are doing here.

> > +		if (has_sha1_file(remote)
> > +				&& parse_object(remote)->flags & COMPLETE) {
> > +			if (rev_command_len + 44 < sizeof(rev_command)) {
> > +				snprintf(rev_command + rev_command_len, 44,
> > +					" ^%s^", sha1_to_hex(remote));
> > +				rev_command_len += 43;
> > +			}
> 
> This rev-list command is to generate the list of "have", and we
> learned that the other side says she has remote -- we choose not
> to tell her that we have ancestors of it, but we do tell her
> about the remote head itself.
> 
> Let's draw a single strand of pearl case to illustrate.  You
> have a commit chain A->B->C->D, and the other end says she has
> C.  At this point, telling her that you have C is enough, and by
> not telling her about A and B, you would save her from depreting
> MAX_HAVE slots.  Of course, if the other end has D as another
> head, then the above logic would give "^D^" to rev-list as well,
> telling it not to tell her about C, but that is what we want --
> because she already knows you have C too when you tell her that
> you have D.  I think I like this optimization.
> 
> One thing that might help, when we are telling the other end
> about what we have, is an output ordering option to get-rev-list
> that shows not in chronological order, but in the order of
> distance from the tip.  That may give the other end a better
> chance to find the latest (in commit order) common commit in
> each branch without running out is MAX_HAS buffer.