git-squash-merge-tree-hash-diagnosis

A branch shows commits ahead after a squash merge because squash merges create a new commit on main without recording the original branch commits, leaving the branch history intact and appearing divergent. Comparing tree hashes confirms the file state is actually identical.

To check if a branch was absorbed by a squash merge, compare the branch tree hash with origin/main using git. If the tree hashes match, the file contents are identical, proving the work was fully integrated and only ghost commits remain.

The best way to clean up branches after a squash merge is to verify tree hashes match, then safely reset your divergent local main to origin/main and delete the fully integrated branch, avoiding misleading rebase or cherry-pick checks.

Cherry-pick checks and three-dot diffs mislead you after a squash merge because they rely on commit history rather than file state. Since squash merges rewrite commit ancestry, these methods fail to recognize identical tree hashes.

You should reset local main instead of rebasing when tree hash verification proves your branch contains only ghost commits. Rebasing would replay empty commits, while resetting aligns your local main directly with origin/main.

Comparing tree hashes diagnoses ghost commits by proving file content parity between a branch and origin/main. If the hashes match despite divergent commit graphs, it confirms the branch holds no new work and only contains ghost commits.