From: Matt Mackall <firstname.lastname@example.org> To: linux-kernel <email@example.com> Subject: Mercurial v0.1 - a minimal scalable distributed SCM Date: Wed, 20 Apr 2005 03:10:54 -0700 Message-ID: <20050420101054.GE21897@waste.org> (raw) http://selenic.com/mercurial/ April 19, 2005 I've spent the past couple weeks working on a completely new proof-of-concept SCM. The goals: - to initially be as simple (and thereby hackable) as possible - to be as scalable as possible - to be memory, disk, and bandwidth efficient - to be able to do "clone/branch and pull/sync" style development It's still very early on, but I think I'm doing surprisingly well. Now that I've got something that actually does some interesting things if you poke at it right, I figure it's time to throw it out there. Here's what I've got so far: - O(1) file revision storage and retrieval with efficient delta compression - efficient append-only layout for rsync and http range protocols - bare bones commit, checkout, stat, history - working "clone/branch" and "pull/sync" functionality - functional enough to be self-hosting - all in less than 600 lines of Python When I say "pull/sync" works, that means I can do: hg merge other-repo and it will pull all "changesets/deltas" that are in other-dir that I don't have, merge them into the changeset history graph, and do the same for all files changed for those deltas. It will call out to a user-specified merge tool like tkdiff for a proper 3-way merge with the nearest common ancestor in the case of conflicts. Right now, "cloning/branching" is simply a matter of "cp -al" or "rsync" (mercurial knows how to break hardlinks if needed). Some benchmarks from my laptop: - prepare for commit of Linux 2.6.10: ~1s - commit Linux 2.6.10: 27s - checkout Linux 2.6.10: 45s - full tree stat for added/changed/deleted files: <1s - local hardlink clone: 1.5s - empty merge between full trees: <.1s - trivial 3-way merge with changes to Makefile: ~1s Much thought has gone into what the best asymptotic performance can be for the various things an SCM has to do and the core algorithms and data structures here should scale relatively painlessly to arbitrary numbers of changesets, files, and file revisions. What remains to be done: - a halfway-usable command line tool - remote (network) repository support - diff generation - changelog entry editing - various manual interventions for merge - handle rename - handle rollback - all sorts of other error handling - all sorts of cleanup, packaging, documentation, testing... Sample usage: export HGMERGE=tkmerge # set a 3-way merge tool mkdir foo hg create # create a repository in .hg/ echo foo > Makefile hg add Makefile # add a file to the current changeset hg commit # commit files currently marked for add or delete hg history # show all changesets hg index Makefile # show change touch Makefile hg stat # find changed files cd ..; cp -al foo branch # make a branch hg merge ../branch-foo # sync changesets from a branch  though the repository format is still in flux -- Mathematics is the supreme nostalgia of our time.
next reply index Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2005-04-20 10:10 Matt Mackall [this message] 2005-04-22 16:21 ` Bill Davidsen
Reply instructions: You may reply publically to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20050420101054.GE21897@waste.org \ --firstname.lastname@example.org \ --email@example.com \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
LKML Archive on lore.kernel.org Archives are clonable: git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git # If you have public-inbox 1.1+ installed, you may # initialize and index your mirror using the following commands: public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \ firstname.lastname@example.org public-inbox-index lkml Example config snippet for mirrors Newsgroup available over NNTP: nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel AGPL code for this site: git clone https://public-inbox.org/public-inbox.git