This describes how you can use msysgit on Windows to work on the Chromium git
repository, without setting up Cygwin or hacking the git cl
, git try
and
other scripts to work under a regular Windows shell.
The basic setup is to set up a regular git checkout on a Linux (or Mac) box, and
use this exclusively to create your branches and run tools such as git cl
, and
have your Windows box treat this git repository as its upstream.
The advantage is, you get a pretty clean setup on your Windows box that is
unlikely to break when the various custom git tools like git cl
change. The
setup is also advantageous if you regularly build code on Windows and then want
to test it on Linux, since all you need to test on your Linux box is a git push
from Windows followed by building and testing under Linux.
The disadvantage is that it adds an extra layer between the Chromium git repo and your Windows checkout. In my experience (joi@chromium.org) this does not actually slow you down much, if at all.
The most frequently used alternative to this workflow on Windows seems to be using Cygwin and creating a checkout directly according to the instructions at UsingGit. The advantage of that approach is you lose the extra overhead, the disadvantage seems to be mostly speed and having to run a Cygwin shell rather than just a normal Windows cmd.
Please note that the instructions below are mostly from memory so they may be slightly incorrect and steps may be missing. Please feel free to update the page with corrections and additions based on your experience.
Create your checkouts:
- Create a git checkout on your Linux box, with read/write abilities, as per UsingGit. The rest of these instructions assume it is located at /home/username/chrome
- Install msysgit on your Windows box.
Starting a new topic branch:
- Linux:
git branch mytopic
(or you may want to use e.g. the LKGR script from UsingGit). - Windows:
git fetch
thengit checkout mytopic
Normal workflow on Windows:
- ...edit/add some files...
git commit -a -m "my awesome change"
- ...edit more...
git commit -a -m "follow-up awesomeness"
git push
Normal workflow on Linux:
- (after
git push
from windows):git cl upload && git try
- (after LGTM and successful try):
git cl commit
(but note thetot-mytopic
trick in the pipelining section below)
Avoiding excessive file changes (to limit amount of Visual Studio rebuilds when switching between branches):
- Base all your different topic branches off of the same base branch; I
generally create a new LKGR branch once every 2-3 working days and then
git merge
it to all of my topic branches. - To track which base branch topic branches are based off, you can use a naming convention; I use e.g. lk0426 for an LKGR branch created April 26th, then use e.g. lk0426-topic1, lk0426-topic2 for the topic branches that have all changes merged from lk0426. I (joi@chromium.org) also have a script to update the base branch for topic branches and rename them - let me know if interested.
- Now that all your branch names are prefixed with the base revision (whether
you use my naming convention or not), you can know before hand when you
switch between branches on Windows whether you should expect a major
rebuild, or a minor rebuild. If you are able to remember which of your
topic branches have gn changes and which don't (or I guess you could use
git diff
to figure this out), then you will also have a good idea whether you need to rungclient runhooks
or not when you switch branches. Another nice thing is that you should never have to rungclient sync
when you switch between branches with the same base revision, unless some of your branches have changes to DEPS files.
Pipelining:
- Linux:
git checkout lk0426-mytopic
git checkout -b lk0426-mytopic-nextstep
- Windows:
git fetch && git checkout lk0426-mytopic-nextstep
- ...work as usual...
git push
- Later, on Linux:
make_new_lkgr_branch lk0428
git merge lk0428 lk0426-mytopic
git branch -m lk0426-mytopic lk0428-mytopic
(to rename)git merge lk0428-mytopic lk0426-mytopic-nextstep
git branch -m lk0428-mytopic-nextstep lk0428-mytopic-nextstep
(to rename)
- Later, when you want to commit one of the earlier changes in the pipeline; all on Linux. The reason you may want to create the separate tip-of-tree branch is in case the try bots show your change failing on tip-of-tree and you need to do significant additional work, this avoids having to roll back the tip-of-tree merge:
Janitorial work on Windows:
- When you rename branches on the Linux side, the Windows repo will not know
automatically; so if you already had a branch
lk0426-mytopic
open on Windows and thengit fetch
, you will still havelk0426-mytopic
even if that was renamed on the Linux side tolk0428-mytopic
. - Dealing with this is straight-forward; you just
git checkout lk0428-mytopic
to switch to the renamed (and likely updated) branch. Thengit branch -d lk0426-mytopic
to get rid of the tracking branch for the older name. Then, occasionally,git remotes prune origin
to prune remote tracking branches (you don't normally see these listed unless you dogit branch -a
).
Gotchas:
- You should normally create your branches on Linux only, so that the Windows repo gets tracking branches for them. Any branches you create in the Windows repo would be local to that repository, and so will be non-trivial to push to Linux.
git push
from Windows will fail if your Linux repo is checked out to the same branch. It is easy to switch back manually, but I also have a script I callsafepush
that switches the Linux-side branch for you before pushing; let me (joi@chromium.org) know if interested.