Git & GitHub

You can explain what Git stores and recover work that looks deleted.

1. 1Snapshots, not diffsYou can apply this in a live incident: Git stores snapshots of the whole tree, with unchanged files reused by hash.12m30xp
2. 2The three treesYou can apply this in a live incident: HEAD is the last commit, the index is the next snapshot, the working tree is the files.12m30xp
3. 3Add and commitYou can apply this in a live incident: git add copies a file from the worktree into the index.12m30xp
4. 4Status and diffYou can apply this in a live incident: status names the files; diff shows the hunks.12m30xp
5. 5Log as a graphYou can apply this in a live incident: Log walks reachable commits from the starting refs.12m30xp
6. 6A branch is a pointerYou can apply this in a live incident: A branch is a movable name for a commit.12m30xp
7. 7Switching branchesYou can apply this in a live incident: switch updates HEAD, the index and the worktree to match the target.12m30xp
8. 8Fast-forward versus merge commitsYou can apply this in a live incident: Fast-forward just moves the pointer when there is no divergence.12m30xp
9. 9Merge conflictsYou can apply this in a live incident: A conflict means both sides edited the same region.12m30xp
10. 10Reflog recoveryYou can apply this in a live incident: Reflog records every movement of HEAD.12m30xp

You can collaborate on GitHub without rewriting anyone else's history by accident.

1. 1Remotes and trackingYou can apply this in a live incident: A remote is a named URL plus fetch refspecs.12m30xp
2. 2Fetch versus pullYou can apply this in a live incident: fetch updates remote-tracking branches only.12m30xp
3. 3Push and force-with-leaseYou can apply this in a live incident: A non-fast-forward push is rejected by default.12m30xp
4. 4RebaseYou can apply this in a live incident: Rebase copies commits onto a new base, creating new hashes.12m30xp
5. 5Pull requestsYou can apply this in a live incident: A pull request is a request to merge one ref into another.12m30xp

You can configure Git and recover work without rewriting shared history.

1. 1git config identityYou can apply this in a live incident: user.name and user.email are recorded on every commit.12m30xp
2. 2init versus cloneYou can apply this in a live incident: clone copies a remote and sets origin.12m30xp
3. 3.gitignoreYou can apply this in a live incident: gitignore only affects untracked files.12m30xp
4. 4git show and blameYou can apply this in a live incident: git show displays a commit and its diff.12m30xp
5. 5stashYou can apply this in a live incident: stash records worktree and optionally index state.12m30xp
6. 6TagsYou can apply this in a live incident: Lightweight tags are names; annotated tags are objects with a message.12m30xp
7. 7restore versus checkoutYou can apply this in a live incident: restore is the modern command to restore files from index or HEAD.12m30xp
8. 8git switch -cYou can apply this in a live incident: switch -c creates a branch and checks it out.12m30xp
9. 9git cleanYou can apply this in a live incident: clean deletes untracked files.12m30xp
10. 10git archiveYou can apply this in a live incident: git archive exports a tree without the .git directory.12m30xp

You can choose revert, reset, cherry-pick and bisect without guessing.

1. 1Cherry-pickYou can apply this in a live incident: Cherry-pick copies a commit's change onto HEAD as a new commit.12m30xp
2. 2Revert versus resetYou can apply this in a live incident: revert adds a new commit that undoes a previous one.12m30xp
3. 3Detached HEADYou can apply this in a live incident: Detached HEAD means HEAD points at a commit, not a branch name.12m30xp
4. 4git bisectYou can apply this in a live incident: bisect binary-searches history between a known good and bad commit.12m30xp
5. 5git notesYou can apply this in a live incident: Notes attach extra blobs to commits without changing the commit hash.12m30xp
6. 6origin/HEADYou can apply this in a live incident: origin/HEAD is the remote's default branch pointer.12m30xp
7. 7fetch --pruneYou can apply this in a live incident: fetch updates remote-tracking branches.12m30xp
8. 8Commit and tag signingYou can apply this in a live incident: GPG or SSH signing attaches a signature to commits or tags.12m30xp

You can use GitHub flow, protection and Actions without treating the website as Git.

1. 1Fork versus cloneYou can apply this in a live incident: A fork is a server-side copy under your account.12m30xp
2. 2Protected branchesYou can apply this in a live incident: Protected branches can require PRs, reviews and status checks.12m30xp
3. 3CODEOWNERSYou can apply this in a live incident: CODEOWNERS maps paths to users or teams that must review.12m30xp
4. 4Squash, merge commit and rebase-mergeYou can apply this in a live incident: Merge commit keeps all commits and adds a merge.12m30xp
5. 5GitHub Actions on pull requestsYou can apply this in a live incident: Actions workflows are YAML under .github/workflows.12m30xp
6. 6SubmodulesYou can apply this in a live incident: A submodule records a commit of another repository.12m30xp
7. 7git worktreeYou can apply this in a live incident: worktree adds a second working directory sharing the same object database.12m30xp
8. 8HooksYou can apply this in a live incident: Client hooks live in .git/hooks and are not committed.12m30xp
9. 9sparse-checkoutYou can apply this in a live incident: sparse-checkout limits which paths populate the worktree.12m30xp

You can keep a clone honest without shrinking history by accident.

1. 1gc and fsckYou can apply this in a live incident: gc packs and expires unreachable objects.12m30xp
2. 2rerereYou can apply this in a live incident: rerere records a conflict resolution and replays it.12m30xp

You can keep remotes, amends and attributes from surprising a teammate.

1. 1commit --amendYou can apply this in a live incident: amend replaces the tip commit with a new hash if it has not been rewritten otherwise.12m30xp
2. 2SSH versus HTTPS remotesYou can apply this in a live incident: HTTPS remotes use a credential helper or token.12m30xp
3. 3gitattributesYou can apply this in a live incident: attributes set line endings, diff drivers and merge behaviour per path.12m30xp
4. 4Partial clone and bloblessYou can apply this in a live incident: Partial clone can omit blobs until checkout needs them.12m30xp
5. 5Shallow clonesYou can apply this in a live incident: A shallow clone truncates history.12m30xp
6. 6Review comments and force-pushYou can apply this in a live incident: Review comments attach to commit line ranges.12m30xp
7. 7Required status checksYou can apply this in a live incident: Required checks match a context name from the status API or check run.12m30xp
8. 8rerereYou can apply this in a live incident: rerere records conflict resolutions.12m30xp