|
|
|
|
@ -1,186 +0,0 @@
|
|
|
|
|
=========================== WHY USE GIT+TOPGIT? ==========================
|
|
|
|
|
|
|
|
|
|
Three major concerns were on our mind when setting up this project.
|
|
|
|
|
|
|
|
|
|
o First we needed to structure the project in such a way that it would be
|
|
|
|
|
easy to rebase all of our changes on the latest official ZFS release
|
|
|
|
|
from Sun. We absolutely need to be able to benefit from the upstream
|
|
|
|
|
improvements and not get locked in to an old version of the code base.
|
|
|
|
|
|
|
|
|
|
o Secondly, we wanted to be able to easily manage our changes in terms
|
|
|
|
|
of a patch stack or graph. This allows us to easily isolate specific
|
|
|
|
|
changes and push them upstream for inclusion. It also allows us to
|
|
|
|
|
easily update or drop specific changes based on what occurs upstream.
|
|
|
|
|
|
|
|
|
|
o Thirdly we needed our DVCS to be integrated with the management of this
|
|
|
|
|
patch stack or graph. We have tried other methods in the past such as
|
|
|
|
|
SVN+Quilt but have found managing the patch stack becomes cumbersome.
|
|
|
|
|
By using Git+TopGit to more tightly integrate our patches in to the repo
|
|
|
|
|
we expect several benefits. One of the most important will be the
|
|
|
|
|
ability to easily work on the patch's with a distributed development
|
|
|
|
|
team, additionally the repo can track patch history, and we can utilize
|
|
|
|
|
Git to merge patches and resolve conflicts.
|
|
|
|
|
|
|
|
|
|
TopGit is designed to specifically address these concerns by providing
|
|
|
|
|
tools to simplify the handling of large numbers of interdependent topic
|
|
|
|
|
branches. When using a TopGit aware repo every topic branch represents
|
|
|
|
|
a 'patch' and that branch references its dependent branches. The union
|
|
|
|
|
of all these branches is your final source base.
|
|
|
|
|
|
|
|
|
|
========================= SETTING UP GIT+TOPGIT ==========================
|
|
|
|
|
|
|
|
|
|
First off you need to install a Git package on your system. For my
|
|
|
|
|
purposes I have been working on a RHEL5 system with git version 1.5.4.5
|
|
|
|
|
installed and it has been working well. You will also need to go get
|
|
|
|
|
the latest version of TopGit which likely is not packaged nicely so you
|
|
|
|
|
will need to build it from source. You can use Git to clone TopGit
|
|
|
|
|
from the official site here and your all set:
|
|
|
|
|
|
|
|
|
|
> git clone git://repo.or.cz/w/topgit.git
|
|
|
|
|
> make
|
|
|
|
|
> make install # Default installs to $(HOME)
|
|
|
|
|
|
|
|
|
|
========================== TOPGIT AND ZFS ================================
|
|
|
|
|
|
|
|
|
|
One you have Git and TopGit installed you will want to clone a copy of
|
|
|
|
|
the Linux ZFS repo. While this project does not yet have a public home
|
|
|
|
|
it hopefully will some day. In the meanwhile if you have VPN access to
|
|
|
|
|
LLNL you can clone the latest official repo here. Cloning a TopGit
|
|
|
|
|
controlled repo is very similar to cloning a normal Git repo, but you
|
|
|
|
|
need to remember to use 'tg remote' to populate all topic branches.
|
|
|
|
|
|
|
|
|
|
> git clone http://eris.llnl.gov/git/zfs.git zfs
|
|
|
|
|
> cd zfs
|
|
|
|
|
> tg remote --populate origin
|
|
|
|
|
|
|
|
|
|
Now that you have the Linux ZFS repo the first thing you will probably
|
|
|
|
|
want to do is have a look at all the topic branches. TopGit provides
|
|
|
|
|
a summary command which shows all the branches and a brief summary for
|
|
|
|
|
each branch obtained from the .topmsg files.
|
|
|
|
|
|
|
|
|
|
> tg summary
|
|
|
|
|
0 feature-branch [PATCH] feature-branch
|
|
|
|
|
feature-commit-cb [PATCH] feature commit cb
|
|
|
|
|
feature-zap-cursor-to-key [PATCH] feature zap cursor to key
|
|
|
|
|
...
|
|
|
|
|
|
|
|
|
|
By convention all TopGit branches are usually prefixed with 't/', however
|
|
|
|
|
I have chosen not to do this for simplicity. A different convention I have
|
|
|
|
|
adopted is to tag the top most TopGit branch as 'top' for easy reference.
|
|
|
|
|
This provides a consistent label to be used when you need to reference the
|
|
|
|
|
branch which contains the union of all topic branches.
|
|
|
|
|
|
|
|
|
|
One thing you may also notice about the 'tg summary' command is it does
|
|
|
|
|
not show the branches in dependent order. This is done because TopGit allows
|
|
|
|
|
each branch to express multiple dependencies as a DAC. Initially this seemed
|
|
|
|
|
like an added complication which I planned to avoid by just implementing a
|
|
|
|
|
stack using the graph. However, this ended up being problematic because
|
|
|
|
|
with a stack when a change was made to a branch near the base, it was a
|
|
|
|
|
very expensive operation to merge the change up to the top of the stack.
|
|
|
|
|
By defining the dependencies as a graph it is possible to keep the depth
|
|
|
|
|
much shallower thus minimizing the merging. It has also proved insightful
|
|
|
|
|
as to each patches actual dependencies.
|
|
|
|
|
|
|
|
|
|
To see the dependencies you will need to use the --graphviz option and pipe
|
|
|
|
|
the result to dot for display. The following command works fairly well for
|
|
|
|
|
me. Longer term it would be nice to update this option to use a preferred
|
|
|
|
|
config options stored in the repo.
|
|
|
|
|
|
|
|
|
|
> tg summary --graphviz | dot -Txlib -Nfontsize=8
|
|
|
|
|
|
|
|
|
|
========================= UPDATING A TOPIC BRANCH ========================
|
|
|
|
|
|
|
|
|
|
Updating a topic branch in TopGit is a pretty straight forward but there
|
|
|
|
|
are a few rules you need to be aware of. The basic process involves
|
|
|
|
|
checking out the relevant topic branch where the changes need to be made,
|
|
|
|
|
making the changes, committing the changes to the branch and then merging
|
|
|
|
|
those changes in to dependent branches. TopGit provides some tools to make
|
|
|
|
|
this pretty easy, although it may be a little sluggish depending on how many
|
|
|
|
|
dependent branches are impacted by the change. Here is an example:
|
|
|
|
|
|
|
|
|
|
> git checkout modify-topic-branch # Checkout the proper branch
|
|
|
|
|
> ...update branch... # Update the branch
|
|
|
|
|
> git commit -a # Commit your changes
|
|
|
|
|
> git checkout top # Checkout the top branch
|
|
|
|
|
> tg update # Recursively merge in new branch
|
|
|
|
|
|
|
|
|
|
Assuming you change does not introduce any conflicts your done. All branches
|
|
|
|
|
were dependent on your change will have had the changed merged in. If your
|
|
|
|
|
change introduced a conflict you will need to resolve the conflict and then
|
|
|
|
|
continue on with the update.
|
|
|
|
|
|
|
|
|
|
========================== ADDING A TOPIC BRANCH =========================
|
|
|
|
|
|
|
|
|
|
Adding a topic branch in TopGit can be pretty straight forward. If your
|
|
|
|
|
adding a non-conflicting patch in parallel with other patches of the same
|
|
|
|
|
type, then things are pretty easy and TopGit does all the work.
|
|
|
|
|
|
|
|
|
|
> git co existing-topic-branch # Checkout the branch to add after
|
|
|
|
|
> tg create new-topic-branch # Create a new topic branch
|
|
|
|
|
> ...update .topmsg... # Update the branch message
|
|
|
|
|
> ...create patch... # Update with your changes
|
|
|
|
|
> git commit -a # Commit your changes
|
|
|
|
|
> git co dependent-topic-branch # Checkout dependent branch
|
|
|
|
|
> tg depend add new-topic-branch # Update dependencies
|
|
|
|
|
> git checkout top # Checkout the top branch
|
|
|
|
|
> tg update # Recursively merge in new branch
|
|
|
|
|
|
|
|
|
|
If you need to add your patch in series with another change things are
|
|
|
|
|
a little more complicated. In this case TopGit does not yet support removing
|
|
|
|
|
dependencies so you will need to do it by hand, as follows.
|
|
|
|
|
|
|
|
|
|
> git co existing-topic-branch # Checkout the branch to add after
|
|
|
|
|
> tg create new-topic-branch # Create a new topic branch
|
|
|
|
|
> ...update .topmsg... # Update the branch message
|
|
|
|
|
> ...create patch... # Update with your changes
|
|
|
|
|
> git commit -a # Commit your changes
|
|
|
|
|
> git co dependent-topic-branch # Checkout dependent branch
|
|
|
|
|
> ...update .topdeps... # Manually update dependencies
|
|
|
|
|
> git commit -a # Commit your changes
|
|
|
|
|
> tg update # TopGit update
|
|
|
|
|
> git checkout top # Checkout the top branch
|
|
|
|
|
> tg update # Recursively merge in new branch
|
|
|
|
|
|
|
|
|
|
Once your done, I find it is a good idea view the repo using the
|
|
|
|
|
'tg summary --graphviz' command and verify the updated dependency graph.
|
|
|
|
|
|
|
|
|
|
========================= REMOVING A TOPIC BRANCH ========================
|
|
|
|
|
|
|
|
|
|
Removing a topic branch in TopGit is also currently not very easy. To remove
|
|
|
|
|
a dependent branch the basic process is to commit a patch which reverts all
|
|
|
|
|
changes on the branch. Then that reversion must be merged in to all dependent
|
|
|
|
|
branches, the dependencies manually updated and finally the branch removed.
|
|
|
|
|
If the branch is not empty you will not be able to remove it.
|
|
|
|
|
|
|
|
|
|
> git co delete-topic-branch # Checkout the branch to delete
|
|
|
|
|
> tg patch | patch -R -p1 # Revert all branch changes
|
|
|
|
|
> git commit -a # Commit your changes
|
|
|
|
|
> git checkout top # Checkout the top branch
|
|
|
|
|
> tg update # Recursively merge revert
|
|
|
|
|
> git co dependent-topic-branch # Checkout dependent branch
|
|
|
|
|
> ...update .topdeps... # Manually update dependencies
|
|
|
|
|
> git commit -a # Commit your changes
|
|
|
|
|
> tg delete delete-topic-branch # Delete empty topic branch
|
|
|
|
|
|
|
|
|
|
Once your done, I find it is a good idea view the repo using the
|
|
|
|
|
'tg summary --graphviz' command and verify the updated dependency graph.
|
|
|
|
|
|
|
|
|
|
============================ TOPGIT TODO =================================
|
|
|
|
|
|
|
|
|
|
TopGit is still a young package which seems to be under active development
|
|
|
|
|
by its author. It provides the minimum set of commands needed but there
|
|
|
|
|
are clearly areas which simply have not yet been implemented. My short
|
|
|
|
|
list of features includes:
|
|
|
|
|
|
|
|
|
|
o 'tg summary --deps', option to display a text version of the topic
|
|
|
|
|
branch dependency DAC.
|
|
|
|
|
|
|
|
|
|
o 'tg depend list', list all topic branch dependencies.
|
|
|
|
|
|
|
|
|
|
o 'tg depend delete', cleanly remove a topic branch dependency.
|
|
|
|
|
|
|
|
|
|
o 'tg create', cleanly insert a topic branch in the middle
|
|
|
|
|
of the graph and properly take care updating all dependencies.
|
|
|
|
|
|
|
|
|
|
o 'tg delete', cleanly delete a topic branch in the middle
|
|
|
|
|
of the graph and properly take care updating all dependencies.
|
Brian Behlendorf