+++ /dev/null
-=========================== 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/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 git://eris.llnl.gov/zfs.git
- > cd zfs
- > tg remote --populate origin
-
-Alternately, if you don't want to worry about using TopGit on your system
-you can simply clone the repo and then checkout the origin/top branch. At
-this point you can simply create a new branch to track your changes. You
-can then feed your patch back to the official repo maintainers to be merged
-in to the proper topic branches.
-
- > git clone git://eris.llnl.gov/zfs.git
- > cd zfs
- > git checkout origin/top
- > git checkout -b <new_branch_name>
-
-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.
git://git.camperquake.de / zfs.git / commitdiff