From: Johannes Schindelin Date: Thu, 20 Oct 2005 01:51:18 GMT Subject: Re: [PATCH] Do not send "want" lines for complete objects Message-ID: In-Reply-To: <7vzmp5xfwu.fsf@assigned-by-dhcp.cox.net> Hi, On Wed, 19 Oct 2005, Junio C Hamano wrote: > Johannes Schindelin 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. Sure. You are thinking along chronological lines. Okay. > > + 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. That was my idea. Ciao, Dscho