Git & GitHub Highlights Summary

Every highlight bullet from the 9 pages in this section, gathered on one page and grouped by the page it came from.

The Git Object Model

• A commit is a full snapshot of the whole repo tree plus a parent pointer - not a diff
• A branch is just a movable pointer to one commit - creating one is nearly free
• A Jupyter notebook's diff noise comes from output cells being part of the tracked snapshot, not from Git itself
• Rebase creates brand-new commits with new hashes - it never edits the originals in place

Essential Git Commands

• status, diff, log, add, commit, push cover daily loops
• stash and restore save context switches without junk commits
• show and blame debug regressions with file history
• fetch and pull --rebase keep feature branches current
• Commit uv.lock and pyproject.toml together on dep changes

Branching & Merging

• Short-lived feat branches rebased onto main daily
• Squash merge features; cherry-pick hotfixes to release lanes
• Never merge main into release/* - cherry-pick fixes only
• Resolve conflicts with tests and lockfile care
• Protect main with required CI: ruff, pytest, mypy

Merge Conflict Resolution Checklist

• Stop, identify conflicted files, and understand both sides before editing
• Regenerate uv.lock - never hand-edit lockfile conflict markers
• Run pytest and ruff after every conflict resolution
• Abort rebase if scope exploded - reset and merge instead
• Ask for help when migrations or shared schemas conflict

Git Worktrees

• git worktree add creates second directory same repo
• Review PR in worktree while keeping WIP on main checkout
• Each worktree needs its own .venv or uv sync
• Remove worktrees with git worktree remove when done
• Avoid two worktrees running migrations on same local DB

GitHub CLI

• gh pr create links commits to tickets and templates
• gh run watch streams CI without browser tab
• gh api for scripted org automation
• Authenticate with gh auth login SSH or HTTPS
• Same uv/pytest commands locally as GitHub Actions

Git for Data/Notebooks

• nbstripout strips outputs before commit - diffs stay reviewable
• Git LFS for parquet, checkpoints, and large CSV artifacts
• Never commit raw datasets with PII - use DVC or cloud URIs
• Jupytext pairs .ipynb with .py for cleaner PRs
• pre-commit hooks enforce strip and file size limits

Git Configuration

• user.name and user.email required for auditable commits
• pull.rebase preserves linear history on feature branches
• pre-commit runs ruff and nbstripout before commit
• aliases shorten log, checkout, and sync workflows
• Signed commits when org policy mandates

Git Best Practices

• main stays shippable with green ruff and pytest
• Commit uv.lock with every dependency change
• Ticket IDs in commits for cherry-pick traceability
• Never force-push shared branches
• pre-commit mirrors CI scripts exactly

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