The depot_tools checkout used for building Chromium is updated by default each time the
automate-git.py script is run. This is problematic when building stable branches because the changes to depot_tools are not always backwards compatible (recent examples here, here and here). We should add the capability to pin known-good depot_tools versions (commit hashes) for stable branches to avoid unexpected breakages.
This can work as follows:
- Add a new
CHROMIUM_BUILD_COMPATIBILITY.txtto be specified when a release branch is created.
automate-git.pyto checkout that value, if specified.
We should continue to build master without depot_tools checkout pinning as an early warning system for breaking changes.