What is the git commit-graph feature?

The commit-graph is a binary cache file (.git/objects/info/commit-graph) that stores a precomputed representation of the commit graph — parent pointers, commit dates, root tree hashes, and generation numbers. It dramatically speeds up Git operations that need to traverse commit history: git log, git merge-base, reachability queries. Without commit-graph, Git must parse commit objects one by one by loading from disk. With commit-graph, the traversal uses the binary cache — 10-100x faster for large repos. Generation numbers: each commit has a generation number (1 + max of parent generation numbers). This allows efficient "is commit A an ancestor of commit B?" queries without full traversal — if A's generation number > B's, A cannot be an ancestor. Enable: git config --global core.commitGraph true; git config --global fetch.writeCommitGraph true — update on fetch. Generate: git commit-graph write --reachable. Update: git commit-graph write --reachable --changed-paths (also stores bloom filters for path-based queries — enables fast git log -- path). This feature is especially impactful for large monorepos with hundreds of thousands of commits.