mockbuild: don't use short commit ids

The length of these is not predictable. It depends on the shortest
unique prefix in the repository and git configuration.

Just use the full one, which also makes it easier to copy the id from
`git log` or GitHub.

schutzbot/mockbuild.sh

@@ -33,7 +33,7 @@ sudo dnf -y install createrepo_c make mock rpm-build s3cmd
 MOCK_CONFIG="${ID}-${VERSION_ID%.*}-$(uname -m)"
 
 # The commit this script operates on.
-COMMIT=$(git rev-parse --short HEAD)
+COMMIT=$(git rev-parse HEAD)
 
 # Bucket in S3 where our artifacts are uploaded
 REPO_BUCKET=osbuild-composer-repos