Allowing commits that break builds means the commit history will include commits that represent broken code. CI is much more useful when the CI implements a pre-commit policy which requires the commit to pass a CI (bamboo) build prior to being accepted as a commit. If the CI build fails, the push to Stash should fail with the appropriate error message(s) and the developer should fix their branch and attempt push to Stash with corrected code. Having this capability completely changes developer culture in that developers must be proactive rather than reactive.

In a feature branch development model, the pre-commit verification would ensure that the feature + baseline builds as a minimum commit requirement. That would be a good starting point. My assumption here is that Bamboo and Stash would work together to enable this functionality. Stash should see the intent to commit and Bamboo should validate pre-commit conditions. Once validated, Stash should accept or reject the commit accordingly.