Git Revision Selection and Ancestry Queries Quiz

Review

1. What does `MERGE^2` select on a two-parent merge commit?

   `^n` selects the nth parent directly.
2. What does `MERGE~2` follow?

   `~n` follows the first-parent chain n generations.
3. What does `MERGE^@` name?

   `R^@` is the parent-set shorthand that names all parents.
4. What does `MERGE^!` select?

   `R^!` includes R and excludes its parents and their reachable history.
5. Which expression is equivalent to `MERGE^2..MERGE`?

   `R^-n` is shorthand for `R^n..R`.
6. What does `v1^{commit}` do when v1 is an annotated tag pointing to a commit?

   `^{commit}` requires a commit object and recursively dereferences tag objects.
7. What does `:/fix parser` identify?

   `:/<text>` is a commit-message revision selector that returns the youngest reachable match.
8. What does `HEAD:README.md` name?

   `R:path` names the blob or tree at the specified path in the tree-ish R.
9. For history-walking commands, what is `A...B`?

   The official `gitrevisions` manual defines three-dot syntax as symmetric difference.
10. What is `A..B` shorthand for?

    Two-dot notation is the shorthand for excluding A's reachable set from B's reachable set.
11. What does `git diff A...B` mean?

    The current `git-diff` manual defines `A...B` as `git diff $(git merge-base A B) B`.
12. What does `--ancestry-path` do to a range such as `D..J`?

    The option filters the range to commits that are descendants of the ancestry point and ancestors of the other endpoint.
13. What does `--first-parent` do at a merge?

    The official traversal docs define first-parent traversal as continuing only through the first parent at merges.
14. Why use `git rev-parse --verify R^{commit}` in a script?

    `--verify` validates the revision and `^{commit}` asserts the resulting object type.