It is really helpful. Thanks a lot! 2015-03-08 17:34 GMT+08:00 Duy Nguyen <pclouds@xxxxxxxxx>: > On Sun, Mar 8, 2015 at 3:57 PM, Dongcan Jiang <dongcan.jiang@xxxxxxxxx> wrote: >> Hi, all >> >> After digging into how "git fetch" works, I have found that my previous >> understanding was too rash. I'm sorry for that. >> >> I find that the current workflow of "git fetch --depth" is as follows: >> >> 1. 'fetch module' calls 'git-upload-pack service' via 'transport module' >> to fetch ref with `depth`. >> 2. Such call is finished by pipe I/O. >> 3. git-upload-pack receives arguments such as 'depth' to fetch commits, >> and send back to the caller. >> >> Therefore, if we want to implement "--deepen" for "git fetch", we have to >> modify the arguments protocol of git-upload-pack service by adding the >> 'shallow commit' hash. >> Then, we can fetch `depth` commits before the 'shallow commit' in >> git-upload-pack service. >> Apparently, we have to output error message when the 'shallow commit' hash >> is not in the repository. > > Close. You can't figure this shallow commit hash from client side > (client repo is shortened). So you can't send it. What you send is > exactly what the user gives you (e.g. --deepen=5, then you send > "deepen 5" or similar). The server side (git-upload-pack) knows about > the shallow boundary of the client and can walk its (i.e. server-side) > commit graph to find out the new, deepened boundary. Then the server > sends necessary objects plus instructions to update shallow boundary > to the client. > > Also, I think this work would include support for smart-http > protocol. It goes a slightly different route, "git fetch" ends up at > transport.c, but then transport-helper.c and calls git-remote-http(s) > which is implemented by remote-curl.c. This one handles http stuff > then passes control to git-fetch-pack.c. It's fetch-pack that talks to > upload-pack.c > > Have a look at Documentation/technical/pack-protocol.txt and > protocol-capabilities.txt (and http-protocol.txt for smart-http). The > function that "draws" shallow boundary based on --depth is > get_shallow_commits() in shallow.c. I suspect you need to improve it a > bit to use with --deepen. I guess you can look at these [1]. Those > changes touch shallow repo in a bit different way, but the main code > path is more or less the same (smart-http not touched). > > [1] https://github.com/pclouds/git/commits/7edde8b83a20abb3cd404e2c5f07e3c29a2891f7 > -- > Duy -- 江东灿（Dongcan Jiang） Team of Search Engine & Web Mining School of Electronic Engineering & Computer Science Peking University, Beijing, 100871, P.R.China -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html