You may encounter the following error messages when running a git push from a CI platform, such as Circle CI, Travis CI, Jenkins and others: 
error: Could not read COMMIT_HASH
fatal: revision walk setup failed
fatal: reference is not a tree: COMMIT_HASH
! [remote rejected] master -> master (missing necessary objects)
! [remote rejected] master -> master (shallow update not allowed)
(Where COMMIT_HASH is a long hexadecimal number)

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Cause

These errors are all caused by pushing from a shallow clone. Shallow clones are often used by CI platforms to make builds faster, but you can’t push from a shallow clone to another git repository, which is why this fails when you try pushing to Aptible.

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Resolution

To solve this problem, update your build script to run this command before pushing to Aptible: 
git fetch --unshallow || true
If your CI platform uses an old version of git, --unshallow may not be available. In that case, you can try fetching a number of commits large enough to fetch all commits through to the repository root, thus unshallowing your repository: 
git fetch --depth=1000000