[INFO] cloning repository https://github.com/mickvangelderen/incremental
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/mickvangelderen/incremental" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fmickvangelderen%2Fincremental", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fmickvangelderen%2Fincremental'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] 80c9859a0a33af8b196256c0cf65153e447f48ca
[INFO] checking mickvangelderen/incremental against master#69fd5e4059f8840f09f60269bcda23dcdcb77151 for pr-135733
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fmickvangelderen%2Fincremental" "/workspace/builds/worker-4-tc1/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-4-tc1/source'...
[INFO] [stderr] done.
[INFO] [stderr] fatal: update_ref failed for ref 'HEAD': cannot update ref 'refs/heads/master': couldn't write '/workspace/builds/worker-4-tc1/source/.git/refs/heads/master.lock'


failed to checkout https://github.com/mickvangelderen/incremental

Caused by:
    command failed: exit status: 128