Post Git Migration Update! Developer workflow and tools documentation has now largely moved to the man pages provided with depot_tools.
Please see the online version of those docs, and especially the new tutorial page for the most up-to-date information about getting and working with Chromium sources.
Not all the information here has been migrated to the depot_tools docs yet, so this page will stay around for a while as a resource, but where there are discrepancies, the depot_tools pages should be considered authoritative.
If you're new to Git but experienced with Subversion, we recommend following the Git-SVN Crash Course. This guide should help you understand how Git differs from Subversion and how to get up to speed the fastest.
Run gclient TWICE, FROM A CMD WINDOW to download and setup everything else you need. It's important to run twice, and not to use msysgit bash or other non-cmd shells, because otherwise gclient may fail to properly install all its dependencies. Use the "--version" flags just reduce the amount of output spew; it's not necessary for the operations to succeed.
gclient --version gclient --version
After running gclient (twice), depot_tools will now contain a full stand-alone installation of msysgit. If you have a previous installation of msysgit, it is strongly recommended that you use the version installed under depot_tools. This version of msysgit contains custom performance improvements that facilitate working with very large git repositories (like chromium and blink). You can run the shell from the provided version of msysgit using:
/path/to/depot_tools/git-.../bin/sh.exe --login -i
where git-... will depend on which version of msysgit was fetched (e.g. git-1.9.0.chromium.5_bin).
You'll need to manually install:
First, tell git about yourself.
git config --global user.name "My Name"
In the end, ~/.netrc (or %HOME%/_netrc on Windows) should have two lines that look like:
machine chromium.googlesource.com login git-yourusername.chromium.org password <generated pwd>
machine chromium-review.googlesource.com login git-yourusername.chromium.org password <generated pwd>
Make sure that ~/.netrc file's permissions are 0600 as many programs refuse to read .netrc files which are readable by anyone other than you.
On Windows, you must manually create HOME as a per-user environment variable and set it to the same as %USERPROFILE%.
You can check that you have everything set up properly by running tools/check_git_config.py .
If you want to use SVN (optional, only do this if you know you need it), ensure that you have a SVN account and that your login credentials are registered locally via:
svn ls svn://svn.chromium.org/chrome
Password is at https://chromium-access.appspot.com/.
When you first run this, you will be prompted for your credentials, which should then be stored locally. On second run these should automatically log you in, without prompting for credentials, otherwise, make sure "store-passwords" is not explicitly set to "no" in ~/.subversion/servers and ~/.subversion/config.
We will use the fetch tool included in depot_tools to check out Chromium, including all dependencies. This will create a new folder in your current working directory named src.
If you have a slow connection or experiencing long fetch times and not interested in the projects history, you can add a --no-history argument to fetch, as in fetch --no-history chromium, and get a shallow checkout.
fetch --nohooks chromium # 'chromium' may alternatively be one of blink, android, ios, see below. cd src git checkout master # if you are building for Linux only: build/install-build-deps.sh # if you are building for Android: build/install-build-deps-android.sh
Alternatives to 'fetch chromium' are:
fetch chromium # Blink from DEPS (most recent roll) - if you're not working on Blink itself
fetch chromium and fetch blink both fetch both Chromium and Blink, but the two commands fetch different versions of Blink: fetching chromium will get a dated Blink (most recent roll to Chromium), and is sufficient and easier if only working on Chromium, while fetching blink will instead get the latest Blink (ToT), and is useful if working on Blink.
In other words, fetch X if you want to work on X.
Note that, by default, fetch creates a local branch called "master". This can be confusing if you mistake it for the upstream "origin/master". Unless you know what you're doing, you should simply delete this branch as follows:
git checkout origin/master git branch -D master
Note that if e.g. you're developing Blink, you'll want to do this in you Blink directory (likely third_party/WebKit) as well.
Post initial checkout, you should be able to switch between projects via
If you're building Chrome for:
If you'd like to only sync to the last known good revision (lkgr), you can checkout origin/lkgr instead of origin/master. Similarly, the lkcr is available at origin/lkcr.
Update your current branch with
If developing Blink, you'll need to pull Blink as well, as follows:
cd "$CHROMIUM_DIR" && git pull
To speed up updating, using more jobs, for example --jobs=16:
With git you should make all your changes in a local branch. Once your change is committed, you can delete this branch.
Create a local branch named "mywork" and make changes to it.
Commit your change locally (this doesn't commit your change to the SVN or Git server)
git commit -a
If you added new files, you should tell git so by running git add <files> before committing.
Upload your change for review
git cl upload
Send a try job
git cl try
See Contributing code for more detailed git instructions, including how to update your CL when you get review comments.
There's a short tutorial that might be helpful to try before your first change: C++ in Chromium 101.
The preferred way to commit changes is by using the commit queue. If this is not an option, you can commit directly from your git checkout (
If you are a multitasker or want to build chromium for different targets without clobbering each other, then perhaps you'll like the gclient-new-workdir.py script located in depot_tools. The script works by creating a new working directory with symlinks pointing to the git database(s) found in your original chromium checkout. You can have as many working directories as you want without the overhead and hassle of cloning chromium multiple times.
gclient-new-workdir.py /path/to/original/chromium chromium2
[Note, this only applies to branches of src.git. Other repos, particularly from external deps, can and do have their own branching logic, which should be documented by the maintainers of those repos.]
# Make sure you are in 'src'.
From there, 'git cl land' commits to the right branch magically! Edit files, 'git commit', and 'git cl upload' as normal.
To get back to the "trunk":
# Make sure you are in 'src'.
Also, if you need to merge changes to DEPS, see the internal ChromeReleaseBranches?? wiki page for some notes.
Releases are tagged in git with the release version number.
Enumerate your local branches:
Switching from one branch to another: Example: Switching from branch 'branch1' to branch 'branch2'.
We normally do our feature work in branches to keep changes isolated from each other. The recommended workflow is to make local branches off the server master, referred to as the origin/master branch. The
git new-branch branch_nameNote that this is equivalent to the following:
git checkout -b new_branch origin/master
If you have dependent changes, a very productive workflow is to have a branch off a branch. Notably, this means that your patch sets (in Rietveld) will show the separate changes, and be easy to review, rather than showing the merged changes (including irrelevant changes), and means you can commit downstream CLs without having to rebase them after the upstream has landed. Do this as follows:
Now when you update the first branch, you can simply git pull on the second branch as normal to pull in your changes:
Note that these incremental patch sets are easy to review, but cannot be applied to HEAD (because they are based off another branch), so you cannot test them on try bots. To test these, upload the diff from HEAD to a different (test-only) issue and test there:
TEST_ISSUE=$(git cl issue | sed -r 's/[^0-9]*([0-9]*).*/\1/') # Save test issue
To open the test issue in Rietveld:
To try again:
git cl upload -t 'Try again' -f origin/master
...and then when finished, delete the CL to clean up (via Rietveld):
Lastly, when an upstream branch has landed, and you've rebased it so it agrees with master, you can set the downstream branch's upstream branch to be origin/master, which means you can now forget about the earlier branch:
A common variant of "branch off a branch" is splitting up a large CL into pieces. Given a local branch
One way to do this is to split off
This can be done manually, particularly if the files don't overlap, by making a new branch
However, this can be done more cleanly via git. The main points are
You generally want to delete local branches after the changes have been committed to master. It is safest to check that your work has, in fact, been committed before deleting it.
Remember that you can always apply a CL that has been posted via:
git checkout -b myworkfrompatch
...so as long as your CL has been posted, you can easily recover your work. Otherwise, you'll need to dig through the git repository, so be careful.
Simply, if master (remote or local) is up-to-date and your branch has been rebased, git branch -d will delete the branch. If not, it will refuse; to force deletion, use git branch -D. So make sure master is up-to-date, rebase branch, and then try deleting (optionally check manually before).
Beware that if your local branch has many revisions (instead of always amending a single revision), rebasing to master may fail, since it will try to apply the patches incrementally. You can avoid this by squashing your local revisions into a single revision (see 6.4 Git Tools - Rewriting History, or more simply squashing commits with rebase). This may be more trouble than it's worth, but it's the safest way.
To check that the branch has been committed upstream:
git checkout mywork
If there are no differences, delete the branch:
git checkout origin/master
NOTE: If you haven't waited long enough after your commit, it is possible that 'git fetch' did not get your svn commit and git will continue to believe that you have local changes, which will prevent "git branch -d" from succeeding. It's best to redo the steps later, (The repo is updated every 3 minutes) but you can also instruct git to force-delete your branch.
Note that when you delete your branch, it will give you the SHA-1 hash for its tip:
Deleted branch mywork (was 123abc0).
You can then recover the branch via:
git checkout -b mywork 123abc0
If you forget the hash, you can find it via git reflog. (Reference: Can I recover branch after the deletion in git?)
If you commit to master, updating will be messy. (This is a good reason to simply delete master entirely, as noted near the top of this document. You only need to read the remainder of this section if you don't do this.)
You can prevent this by adding a pre-commit hook that checks if you're in master and stops you from doing this. Create a file named chromium/src/.git/hooks/pre-commit and add the below to it, then mark executable. (Blink developers: add in blink directory as well.)
If you've accidentally uploaded a change list from master, you can clear the association of an issue number with master via:
git cl issue 0
If you've accidentally committed to master, then, after copying your work to a new branch (e.g., make patch and then apply to new branch), you can clean up master by deleting your accidental commit as per this answer to How to undo the last Git commit? -- see more details there.
git reset --hard HEAD~1
Sometimes you'll get the message "You have unstaged changes." when you personally don't, often due to a directory that has been moved or delete. You can fix this by moving the directory outside of the repo directory (or deleting it), and then trying gclient sync again.
It is also possible that you're getting this due to local changes (or other problems) in the depot_tools directory. You can fix these by going to depot_tools and resetting:
git reset --hard HEAD
Your source tree includes many other repositories in subdirectories - mainly in third_party, but also elsewhere. See src/DEPS for the full list.
Each subdirectory is its own git tree, so you should start a branch inside a subdirectory if you want to work there. Be sure to commit and checkout master again when you want to sync your tree again later!
If you wish to commit to one of these repositories, you will need to configure git svn like you did for the main Chromium repository.
However, in order to ensure that git cl dcommit will do the right thing, some additional configuration is needed in order to match the svn repository the git mirror is mirroring from.
To do so, run:
And look for the line beginning with git-svn-id: . For example, if you wanted to commit to ffmpeg (src/third_party/ffmpeg), running git log would show something like git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/ffmpeg@12345 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
If the URL starts with svn://svn.chromium.org/svn, the steps are very similar to SVN setup for committers, replacing every occurrence of trunk/src with whatever the path was in the git log command was (eg:trunk/deps/third_party/ffmpeg).
If the URL starts with http://src.chromium.org/svn or https://src.chromium.org/svn, you will need to configure git svn to fetch from that URL, but when committing, to use svn://svn.chromium.org/svn. If the URL was https://, use https://' instead of http://` below:
The key is setting svn-remote.svn.pushurl to the read-write URL of the project, even though the URL passed to git svn init may be the read-only URL.
For projects hosted on code.google.com (for example, gyp) there's slightly different incantations required. For example with gyp:
git svn init https://gyp.googlecode.com/svn -Ttrunk --rewrite-root=http://gyp.googlecode.com/svn
git svn info
From a branch, find the Git Commit ID (SHA1) of the revision you want to revert
Revert the change and commit it locally
git revert <sha1>
Upload for review
git cl upload
git cl dcommit --tbr
Never commit changes to .DEPS.git. This file is maintained by an automated system based on what's in DEPS and your changes will be overwritten.
While Chromium's main source server remains in Subversion, rolling DEPS using the Git workflow requires a couple of extra steps:
1. Start out with a SVN revision you want to roll a given dependency in DEPS to.
2. Find the corresponding Git SHA1 commit ID to the SVN revision you are rolling to. You can use https://chromium.googlesource.com/chromium/src to find the SHA1 commit ID for a given project + SVN revision.
3. Update your .DEPS.git to that project's SHA1 commit ID, testing this change in your Git working copy. When you're through testing, remove this change so you don't accidentally modify .DEPS.git.
4. Modify DEPS to use the desired SVN revision. (Once change on DEPS is committed by you, the automated system commits update on .DEPS.git soon)
If you want to locally test changes to .DEPS.git. You can manually generate .DEPS.git by running (from the src) directory:
python tools/deps2git/deps2git.py -o .DEPS.git -w /path/to/chrome # w/o src
Just remember not to check it in!
If you are developing using a SVN dependency that's not in any of the mirrored Git repos (eg. a development branch), follow these instructions:
1. Make sure your checkout is up-to-date by running 'gclient sync'.
2. Edit src/.DEPS.git to point your dependency at the SVN equivalent for your change. (eg. change 'src/third_party/v8-i18n' to point to http://v8-i18n.googlecode.com/svn/branches/globalization@45)
3. Move or remove that dependency's directory in your checkout (eg. rm -rf src/third_party/v8-i18n)
4. Re-run 'gclient sync' to pull that SVN checkout locally.
5. Verify your change. You're free to test that dependency now. If you used a SVN URL that allows you to commit back to that repo, you can also use it to develop against that repo.
6. Revert your change to src/.DEPS.git. Never commit changes to .DEPS.git.
If you are adding a new repository to pull from, make sure that repository's svn URL can be parsed by the tools by running:
python tools/deps2git/deps2git.py -o .DEPS.git
Don't manually check in changes to .DEPS.git (see "Rolling Deps" above).
Make sure that the repository in question is mirrored at chromium.googlesource.com. To mirror a repository or add a custom URL mapping to deps2git.py, please file an infrastructure ticket.
If the Git command line doesn't work for you, please ensure that your environment variables like EDITOR, HOME, and GIT_SSH are all set to strings not enclosed in double quotes. We have fixed at least one error caused by this previously. It's possible that overusing quotes in your variables will cause other errors, as well.
Check out these links:
After you read those and understand the git-svn commands and workflow, then you'll realize that all git-svn does is set up and manage a new git remote. If you don't know about git remotes, you'll want to learn more about those, too.
Using the Cocoa version of Emacs as the EDITOR environment variable on Mac OS will cause "git commit" to open the message in a window underneath all the others. To fix this, create a shell script somewhere (call it $HOME/bin/EmacsEditor? in this example) containing the following:
and in your .bashrc or similar,
git-cl defaults to using 50% similarity as a threshold for detecting renames. This is sometimes inappropriate, e.g., if splitting off a small file from a large file (in which case you want a smaller threshold, to avoid false negatives), or when adding a small file (in which case you want a larger threshold, to avoid false positives from common boilerplate). This is controlled by the add_git_similarity function in git_cl.py, and you can set threshold to a given value for a branch (saved in config for that branch), or not look for copies on a specific upload (but not saved in config for the branch):
git cl upload --similarity=80 # set threshold to 80% for this branch
Managed mode is a deprecated feature of gclient. It was conceived to give an easier workflow for newcomers to git, but turned out to be full of surprising behaviors. It has thus been deprecated, unmanaged mode is the default, and existing users of managed mode are encouraged to change to unmanaged mode.
To check which mode you are using, check .gclient (the gclient config file) and see the value of the "managed" flag. To switch to unmanaged mode from managed mode:
To make the Blink repo also unmanaged, first fetch blink and then:
The main difference between managed mode and unmanaged mode is that in managed mode, local branches track local master branch instead of origin/master, and gclient “manages” the branches so that they stay in sync. However in practice this leads to two master branches (local master and origin/master) that go out of sync and prevent further uploads/commits. With unmanaged mode you always have only one master: origin/master. The local master still exists but is not treated in any special way by the tools.
If you find yourself needing help with the new workflow, please file a bug with the infrastructure team athttps://code.google.com/p/chromium/issues/entry?template=Build%20Infrastructure