Git commit DAG maps merge parents

The key insight is that Git’s “magic” is just a clean graph data model with cryptographic integrity layered on top.

• –Regular commits usually have one parent; merge commits have two or more, which is why branch history converges without losing lineage.
• –The commit object format in Pro Git explicitly stores parent commit references, making ancestry traversal straightforward.
• –Because each commit hash covers its metadata (including parent pointers), rewriting old history changes downstream hashes and is immediately detectable.
• –This mental model helps developers reason better about `merge`, `rebase`, `cherry-pick`, and `--first-parent` views.