I used git bisect in anger for the first time recently and it felt like magic.
Background: We had two functions in the codebase with identical names and nearly identical implementations, the latter having a subtle bug. Somehow both were imported into a particular python script, but the correct one had always overshadowed the incorrect one - that is, until an unrelated effort to apply code formatting standards to the codebase “fixed” the shadowing problem by removing the import of the correct function. Not exactly mind bending - but, we had looked at the change a few times over in GitHub while debugging and couldn’t find a problem with it - not until we knew for sure that was the commit causing the problem did we find the bug.
Background: We had two functions in the codebase with identical names and nearly identical implementations, the latter having a subtle bug. Somehow both were imported into a particular python script, but the correct one had always overshadowed the incorrect one - that is, until an unrelated effort to apply code formatting standards to the codebase “fixed” the shadowing problem by removing the import of the correct function. Not exactly mind bending - but, we had looked at the change a few times over in GitHub while debugging and couldn’t find a problem with it - not until we knew for sure that was the commit causing the problem did we find the bug.