$BITBUCKET_COMMIT is too short

The $BITBUCKET_COMMIT variable contains a commit hash that is too short. It should be a string with a length of 40, but it a string with a length of 12.

As a consequence, the Codecov Bash uploader uses a commit hash that does not pass validation and I cannot upload reports.

I also reported this to Codecov Support: https://community.codecov.io/t/uploading-report-fails-with-ci-provider-bitbucket/130