When looking up git commits, find_commit.dart uses a git log invocation here:

This is called from here:

Since we hardcode master as both the primary and secondary repo branches, it will fail for repos that have only a main branch and no master, such as flutter/cocoon.

See example failure here:
https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8797370543676737825/+/u/Customer_testing/customer_testing/test_stderr

Related, but we should probably fail whichever tools are using find_commit.dart if the lookup fails. In the log above it looks like even though the lookup fails, we continue on and run the tests anyway:

git -C ../../bin/cache/pkg/tests checkout
dart --enable-asserts run_tests.dart

Note the lack of SHA in the checkout command, which I presume is meant to be there.