[doc][git] playing with git, and netdev/libata-dev trees

Hopefully, this email can quick-start some people on git.

One of the things Linus's new 'git' tool allows me to do is make public the 50+ repositories that were previously only available on my local workstation. This should make it a lot easier for developers to see precisely what I have merged, and makes generating follow-up patches a whole lot easier.

When I merge a patch for drivers/net/forcedeth.c, I merge it into a brand new 'forcedeth' repository, a peer to the 40+ other such repository. Under BitKeeper, I made these repositories available merged together into one big "netdev-2.6" repository because it was too time consuming to make the individual 50+ trees publicly available. With git, developers have direct access to the individual trees.

I thought I would write up a quick guide describing how to mess around with the netdev and libata-dev trees, and with git in general.

1) installing git

git requires bootstrapping, since you must have git installed in order to check out git.git (git repo), and linux-2.6.git (kernel repo). I have put together a bootstrap tarball of today's git repository.

Download tarball from: http://www.kernel.org/pub/linux/kernel/people/jgarzik/git-20050526.tar.bz2

tarball build-deps:  zlib, libcurl

install tarball:  unpack && make && sudo make prefix=/usr/local install

jgarzik helper scripts, not in official git distribution: http://www.kernel.org/pub/linux/kernel/people/jgarzik/git-switch-tree http://www.kernel.org/pub/linux/kernel/people/jgarzik/git-new-branch http://www.kernel.org/pub/linux/kernel/people/jgarzik/git-changes-script

After reading the rest of this document, come back and update your copy of git to the latest: rsync://rsync.kernel.org/pub/scm/linux/kernel/git/torvalds/git.git

2) download a linux kernel tree for the very first time

mkdir -p linux-2.6/.git
cd linux-2.6
rsync -a --delete --verbose --stats --progress \ 
rsync://rsync.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git/ 
\          <- word-wrapped backslash; sigh
    .git/

3) download latest changes to on-disk local tree

cd linux-2.6 git-pull-script \ rsync://rsync.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git

4) check out files from the git repository into the working directory

cd linux-2.6 git-read-tree -m HEAD && git-checkout-cache -q -f -u -a

5) check in your own modifications (e.g. apply a patch)

# go to repo cd linux-2.6

# make some modifications patch -sp1 < /tmp/my.patch diffstat -p1 < /tmp/my.patch

# NOTE: add '--add' and/or '--remove' if files were added or removed git-update-cache <list of all files changed>

# commit changes
GIT_AUTHOR_NAME="John Doe"		\
    GIT_AUTHOR_EMAIL="jdoe@foo.com"	\
    GIT_COMMITTER_NAME="Jeff Garzik"	\
    GIT_COMMITTER_EMAIL="jgarzik@pobox.com"	\
    git-commit-tree `git-write-tree`	\
    -p $(cat .git/HEAD )			\
    < changelog.txt			\
    > .git/HEAD

6) List all changes in working dir, in diff format.

git-diff-cache -p HEAD

7) List all changesets (i.e. show each cset's description text) in local 
tree that are not present in remote tree.

cd my-kernel-tree-2.6 git-changes-script -L ../linux-2.6 | less

8) List all changesets:

git-whatchanged

9) apply all patches in a Berkeley mbox-format file

First, download and add to your PATH Linus's git tools: rsync://rsync.kernel.org/pub/scm/linux/kernel/git/torvalds/git-tools.git

cd my-kernel-tree-2.6 dotest /path/to/mbox # yes, Linus has no taste in naming useful scripts

10) don't forget to download tags from time to time.

git-pull-script only downloads sha1-indexed object data, and the requested remote head. This misses updates to the .git/refs/tags/ and .git/refs/heads directories. It is advisable to update your kernel .git directories periodically with a full rsync command, to make sure you got everything:

cd linux-2.6
rsync -a --delete --verbose --stats --progress \ 
rsync://rsync.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git/ 
\          <- word-wrapped backslash; sigh
    .git/

11) [jg-specific] list all branches found in netdev-2.6 or libata-dev trees.

Download
rsync://rsync.kernel.org/pub/scm/linux/kernel/git/jgarzik/netdev-2.6.git
	or
rsync://rsync.kernel.org/pub/scm/linux/kernel/git/jgarzik/libata-dev.git

cd netdev-2.6 ls .git/refs/heads/

{ these are the current netdev-2.6 branches }

12) [jg-specific] make desired branch current in working directory

git-switch-tree $branch

13) [jg-specific] create a new branch, and make it current

git-new-branch $branch

14) [jg-specific] examine which branch is current

ls -l .git/HEAD

15) undo all local modifications (same as checkout):

git-read-tree -m HEAD && git-checkout-cache -q -f -u -a