Git refuses to merge unrelated histories during a rebase when the branches being rebased do not share a common ancestor. This typically happens when two repositories or branches were initialized separately, causing Git to treat them as entirely distinct histories. To resolve this, you can use the –allow-unrelated-histories flag during the rebase or merge operation. For example, running:
git rebase –allow-unrelated-histories
This command tells Git to allow merging histories that don’t share a common base. Be cautious when using this option, as it may require resolving conflicts between the two unrelated histories.