Chromium usesgclient (part of depot_tools) to manage dependencies (e.g. V8, WebRTC). Information such as URLs and hashes is stored in theDEPS file located in the root of the project. In addition toDEPS,gclient may read git submodules (seedepot_tools submodules support).
gclient supports three dependency types: git,gcs, andcipd.
If the code is in a Git repo that you want to mirror, please file aninfra git ticket to get the repo mirrored onto chromium.googlesource.com; we don't allow direct dependencies on non-Google-hosted repositories, so that we can still build if an external repository goes down.
Once the mirror is set up, you can add the actual dependency intoDEPS.
Add your entry inDEPS. Then rungclient gitmodules to generate git submodules; this will contain the.gitmodule change and gitlink. Edit theOWNERS file and add the gitlink path. Then, rungit add DEPS OWNERS to stage those files for commit, followed bygit commit. Your change is now ready to be sent for a review usinggit cl upload.
For example, if your new dependency is “src/foo/bar.git”, its gitlink path is “foo/bar”, and the top levelOWNERS entry isper-file foo/bar=*. You can confirm this by runninggit status.Example CL.
# manual edit of DEPS and OWNERS file (see changes below). % gclient gitmodules.gitmodules and gitlinks updated. Please check `git diff --staged`and commit those staged changes (`git commit` without -a) % git add OWNERS DEPS # stage files % git diff --cached # see staged changesdiff --git a/.gitmodules b/.gitmodulesindex 29c355fa92e3d..89866442d45aa 100644--- a/.gitmodules+++ b/.gitmodules@@ -1,3 +1,6 @@+[submodule "foo/bar"]+ path = foo/bar+ url = https://chromium.googlesource.com/foo/bar.git [submodule "third_party/clang-format/script"] path = third_party/clang-format/script url = https://chromium.googlesource.com/external/github.com/llvm/llvm-project/clang/tools/clang-format.gitdiff --git a/DEPS b/DEPSindex 44fbc53a0d53a..05481be5066ed 100644--- a/DEPS+++ b/DEPS@@ -555,6 +555,10 @@ allowed_hosts = [ ] deps = {+ 'src/foo/bar': {+ 'url': Var('chromium_git') + '/foo/bar.git' + '@' ++ '1111111111111111111111111111111111111111',+ }, 'src/third_party/clang-format/script': Var('chromium_git') + '/external/github.com/llvm/llvm-project/clang/tools/clang-format.git@' +diff --git a/OWNERS b/OWNERSindex 55bfe60fcb03b..02b4117fca1ea 100644--- a/OWNERS+++ b/OWNERS@@ -37,6 +37,7 @@ per-file README.md=* per-file WATCHLISTS=* # git submodules+per-file foo/bar=* per-file third_party/clang-format/script=* per-file chrome/browser/resources/preinstalled_web_apps/internal=* per-file chrome/installer/mac/third_party/xz/xz=*diff --git a/foo/bar b/foo/barnew file mode 160000index 0000000000000..1111111111111--- /dev/null+++ b/foo/bar@@ -0,0 +1 @@+Subproject commit 1111111111111111111111111111111111111111 % git statusOn branch test_newdepYour branch is up to date with 'origin/main'.Changes to be committed: (use "git restore --staged <file>..." to unstage) modified: .gitmodules modified: DEPS modified: OWNERS new file: foo/barChanges not staged for commit: (use "git add/rm <file>..." to update what will be committed) (use "git restore <file>..." to discard changes in working directory) deleted: foo/bar% # At this point, you can run gclient sync if you want to get the dependency.% # But it's not required, and you can use `git cl upload`. % git commit -m "[DEPS] Example of new dependency"[test_newdep 9731cfb680756] [DEPS] Example of new dependency 4 files changed, 9 insertions(+) create mode 160000 foo/bar % git cl uploadFound change with 1 commit...Running Python 3 presubmit upload checks ...-- snip --remote: https://chromium-review.googlesource.com/c/chromium/src/+/4923074 [DEPS] Example of new dependency [NEW]-- snip --If you need a change in a dependency, the general process is to first contribute the change upstream, thenroll into Chromium. Some projects (e.g. Skia) are autorolled, but it is good practice to manually roll after an upstream change to ensure your change can be successfully rolled and there are no resulting compile or test failures.
Upstream projects have a variety of contribution workflows. The two most common are Gerrit-based reviews usinggit cl upload (like Chromium itself) and GitHub PRs. Some projects have aCONTRIBUTING.md file in their root that gives instructions.
In most cases, creating a standalone checkout/clone of the project you‘re modifying, outside your Chromium checkout, is the best way to ensure you’re contributing to upstreamHEAD and can run the project‘s presubmit checks. Follow the project’s contribution instructions (e.g. runningfetch orgclient sync as needed, possibly after downloading or cloning the source). If you do attempt to create and upload changes directly inside submodules in your Chromium checkout, be careful not to commit the new submodule hashes to any Chromium changes. You may also need tocreate symlinks to enable other projects' presubmits, or else skip them by uploading with--bypass-hooks.
If you want to roll dependency to a specific version, you can do by running the following:
gclient setdep -r {path to dependency}@{hash}For example, let's say you want to roll boringssl in chromium/src to commit e4acd6cb568214b1c7db4e59ce54ea2e1deae1f5. You would run the following:
gclient setdep -r src/third_party/boringssl/src@e4acd6cb568214b1c7db4e59ce54ea2e1deae1f5
Under the hood, gclient understands DEPS file, and knows what needs to update. In the example above, it actually updates boringssl_revision variable that is used in boringssl deps declaration.
Example of DEPS file:vars = { 'boringssl_git': 'https://boringssl.googlesource.com', 'boringssl_revision': 'e4acd6cb568214b1c7db4e59ce54ea2e1deae1f5', } deps = { 'src/third_party/boringssl/src': Var('boringssl_git') + '/boringssl.git' + '@' + Var('boringssl_revision'), }
It also updates gitlink if git submodules are used. Git status will show the following:
$ git status-- snip --Changes to be committed: modified: DEPS modified: third_party/boringssl/src
depot_tools also provides aroll-dep script which can roll the desired repository to the latest commit on main branch.roll-dep handles both DEPS and git submodules.
You can update things yourself by modifying the DEPS file directly. If git submodules are used, you also need to update gitlinks - an entry for submodules in the git database by using:
git update-index --add --cacheinfo 160000,{hash},{path}git update-index instructs git to register git submodule change to the index (ie stages submodule for commit). Particularly, --cacheinfo argument instructs git to directly insert the specified info into the index: 160000 is gitlink mode (used by git submodules), {hash} is a new commit hash you want to roll, and path is relative path to git submodule.
Using the boringssl example above, the following will need to be run inside chromium/src worktree:
git update-index --add --cacheinfo 160000,e4acd6cb568214b1c7db4e59ce54ea2e1deae1f5,third_party/boringssl/src
Once executed,git status will report there is an update to the submodule, which you can commit as any other file change.
Alternatively, you can regenerate git submodules once you update DEPS file (see section below).
gclient doesn't provide a way to delete dependencies. You can delete dependency by manually editing DEPS file and running the following to update git submodules:
export DEPENDENCY={dependency}git rm --cached "$DEPENDENCY"git config -f .gitmodules --remove-section "submodule.$DEPENDENCY"git add .gitmodulesUsing the example from the previous section:
export DEPENDENCY=third_party/boringssl/srcgit rm --cached "$DEPENDENCY"git config -f .gitmodules --remove-section "submodule.$DEPENDENCY"git add .gitmodules
Once the commands are executed, you can proceed with committing your change. You should see change in DEPS, .gitmodule and {dependency}.
If there are many git dependency changes to DEPS file, it may be impractical to manually update-index. For those reasons, gclient provides a convenient way to regenerate git modules entries and to update .gitmodules file.
Once you are done with your DEPS modifications, run the following script in the root of you project:
gclient gitmodules
The script will create a new .gitmodules files and update all gitlinks. Please note that old gitlinks won't be deleted, and you will need to remove them manually (see section above for deleting dependencies).
Creating the following symlinks (POSIX:ln -s DEST SRC, Windows:mklink /D SRC DEST from an Admincmd prompt) will get other projects' presubmit checks working, if you want to upload directly from inside your Chromium checkout and don't want to use--bypass-hooks. All directories assume you are in your Chromiumsrc dir. This list is non-exhaustive; please add to it as necessary.
v8/buildtools tobuildtoolsv8/third_party/depot_tools todepot_toolsthird_party/webrtc/build tobuildthird_party/webrtc/buildtools tobuildtoolsthird_party/src to.