Glosarium
Contents

Engineering Craft

Version Control (Git)

Tracking every change so you can review, undo and collaborate.

Backend Engineer

Junior

Write correct code, ship small changes safely, ask good questions.

Core: start here

  • GitThe distributed version control system almost everyone uses.
  • CommitA snapshot of changes with a message explaining them.
  • .gitignoreFiles Git should never track, like build output and .env.
  • CloneCopying a remote repository, with its full history, to your machine.
  • AmendChanging the most recent commit's content or message.
  • BranchA movable pointer to a line of commits, for isolated work.
  • Commit MessageA summary line plus a body explaining why a change was made.
  • DiffSeeing exactly what changed between commits, branches or your working copy.
  • Log and HistoryBrowsing and filtering commit history.
  • RebaseReplaying commits on top of another base for a linear history.
  • Merge ConflictTwo branches changed the same lines and Git needs you to decide.
20 more junior concepts
  • Git ConfigYour name, email, aliases and defaults, at global or repository level.
  • RepositoryA project's files plus their complete history.
  • Staging AreaWhere you choose which changes go into the next commit.
  • RemoteAnother copy of the repository, usually "origin" on GitHub or GitLab.
  • ForkYour own copy of someone else's repository, for contributing via pull requests.
  • Push, Pull, FetchSending commits, downloading and merging, or only downloading.
  • RevertCreating a new commit that undoes an earlier one.
  • TagA named pointer to a commit, usually marking a release.
  • Version ControlTracking every change to code so you can review, revert and collaborate.
  • Atomic CommitOne commit doing one logical thing, easy to review and revert.
  • BlameSeeing who last changed each line and in which commit.
  • Branch Naming ConventionsNames like feat/login-page that tell people what a branch is for.
  • Conventional CommitsA commit message convention like "feat:" and "fix:" that tools can parse.
  • HEADGit's pointer to the commit you currently have checked out.
  • MergeCombining the histories of two branches.
  • StashTemporarily shelving uncommitted changes.
  • Detached HEADChecking out a commit directly instead of a branch.
  • ResetMoving a branch pointer back, in soft, mixed or hard mode.
  • Force PushOverwriting remote history; use --force-with-lease and never on shared branches.
  • SquashCombining several commits into one.

Mid-level

Own a feature end to end without hand-holding.

Core: start here

  • BisectBinary-searching history to find the commit that introduced a bug.
  • Interactive RebaseRewriting commits: squash, reorder, edit, drop.
  • Merge vs RebasePreserving history as it happened vs rewriting it to be linear.
10 more mid-level concepts

Senior

Own a system, its failure modes, and its trade-offs.

  • Git InternalsBlobs, trees, commits and refs: what Git actually stores.
  • Patch FilesSharing changes as diff files instead of branches.
  • Monorepo vs PolyrepoOne repository for everything vs one per project.
  • WorktreeSeveral working directories checked out from one repository.

Data Analyst

Junior

Write correct SQL, build trusted dashboards, ask good questions.

  • GitThe distributed version control system almost everyone uses.
  • CommitA snapshot of changes with a message explaining them.
  • .gitignoreFiles Git should never track, like build output and .env.
  • RemoteAnother copy of the repository, usually "origin" on GitHub or GitLab.
  • BranchA movable pointer to a line of commits, for isolated work.
  • Push, Pull, FetchSending commits, downloading and merging, or only downloading.
  • Version ControlTracking every change to code so you can review, revert and collaborate.

Mid-level

Own an analysis end to end, from vague question to recommendation.

  • Merge ConflictTwo branches changed the same lines and Git needs you to decide.

Data Engineer

Junior

Build and fix pipelines from clear specs; write correct SQL.

Core: start here

  • GitThe distributed version control system almost everyone uses.
  • CommitA snapshot of changes with a message explaining them.
  • .gitignoreFiles Git should never track, like build output and .env.
  • CloneCopying a remote repository, with its full history, to your machine.
  • AmendChanging the most recent commit's content or message.
  • BranchA movable pointer to a line of commits, for isolated work.
  • Commit MessageA summary line plus a body explaining why a change was made.
  • DiffSeeing exactly what changed between commits, branches or your working copy.
  • Log and HistoryBrowsing and filtering commit history.
  • RebaseReplaying commits on top of another base for a linear history.
  • Merge ConflictTwo branches changed the same lines and Git needs you to decide.
20 more junior concepts
  • Git ConfigYour name, email, aliases and defaults, at global or repository level.
  • RepositoryA project's files plus their complete history.
  • Staging AreaWhere you choose which changes go into the next commit.
  • RemoteAnother copy of the repository, usually "origin" on GitHub or GitLab.
  • ForkYour own copy of someone else's repository, for contributing via pull requests.
  • Push, Pull, FetchSending commits, downloading and merging, or only downloading.
  • RevertCreating a new commit that undoes an earlier one.
  • TagA named pointer to a commit, usually marking a release.
  • Version ControlTracking every change to code so you can review, revert and collaborate.
  • Atomic CommitOne commit doing one logical thing, easy to review and revert.
  • BlameSeeing who last changed each line and in which commit.
  • Branch Naming ConventionsNames like feat/login-page that tell people what a branch is for.
  • Conventional CommitsA commit message convention like "feat:" and "fix:" that tools can parse.
  • HEADGit's pointer to the commit you currently have checked out.
  • MergeCombining the histories of two branches.
  • StashTemporarily shelving uncommitted changes.
  • Detached HEADChecking out a commit directly instead of a branch.
  • ResetMoving a branch pointer back, in soft, mixed or hard mode.
  • Force PushOverwriting remote history; use --force-with-lease and never on shared branches.
  • SquashCombining several commits into one.

Mid-level

Own pipelines and models end to end, including their quality.

  • MonorepoMany projects living in one repository.
  • SubmoduleA repository embedded inside another at a fixed commit.
  • Cherry-PickApplying one specific commit onto another branch.
  • Git HooksScripts that run on Git events, like linting before a commit.
  • Git LFSStoring large binary files outside normal Git history.
  • ReflogGit's log of where HEAD has been; your undo history after disasters.
  • Signed CommitsCryptographically proving who authored a commit.
  • BisectBinary-searching history to find the commit that introduced a bug.
  • Fast-Forward vs Merge CommitMoving a branch pointer ahead vs recording a merge commit.
  • Interactive RebaseRewriting commits: squash, reorder, edit, drop.
  • Merge vs RebasePreserving history as it happened vs rewriting it to be linear.
  • Rewriting Shared HistoryWhy rebasing or force-pushing shared branches breaks teammates.
  • Removing Secrets from Git HistoryPurging a committed secret with git filter-repo, and why you must rotate it anyway.

Senior

Design the platform's storage, processing and modeling choices.

  • Git InternalsBlobs, trees, commits and refs: what Git actually stores.
  • Patch FilesSharing changes as diff files instead of branches.
  • Monorepo vs PolyrepoOne repository for everything vs one per project.
  • WorktreeSeveral working directories checked out from one repository.

Frontend Engineer

Junior

Build UI that works, ship small changes safely, ask good questions.

Core: start here

  • GitThe distributed version control system almost everyone uses.
  • CommitA snapshot of changes with a message explaining them.
  • .gitignoreFiles Git should never track, like build output and .env.
  • CloneCopying a remote repository, with its full history, to your machine.
  • AmendChanging the most recent commit's content or message.
  • BranchA movable pointer to a line of commits, for isolated work.
  • Commit MessageA summary line plus a body explaining why a change was made.
  • DiffSeeing exactly what changed between commits, branches or your working copy.
  • Log and HistoryBrowsing and filtering commit history.
  • RebaseReplaying commits on top of another base for a linear history.
  • Merge ConflictTwo branches changed the same lines and Git needs you to decide.
20 more junior concepts
  • Git ConfigYour name, email, aliases and defaults, at global or repository level.
  • RepositoryA project's files plus their complete history.
  • Staging AreaWhere you choose which changes go into the next commit.
  • RemoteAnother copy of the repository, usually "origin" on GitHub or GitLab.
  • ForkYour own copy of someone else's repository, for contributing via pull requests.
  • Push, Pull, FetchSending commits, downloading and merging, or only downloading.
  • RevertCreating a new commit that undoes an earlier one.
  • TagA named pointer to a commit, usually marking a release.
  • Version ControlTracking every change to code so you can review, revert and collaborate.
  • Atomic CommitOne commit doing one logical thing, easy to review and revert.
  • BlameSeeing who last changed each line and in which commit.
  • Branch Naming ConventionsNames like feat/login-page that tell people what a branch is for.
  • Conventional CommitsA commit message convention like "feat:" and "fix:" that tools can parse.
  • HEADGit's pointer to the commit you currently have checked out.
  • MergeCombining the histories of two branches.
  • StashTemporarily shelving uncommitted changes.
  • Detached HEADChecking out a commit directly instead of a branch.
  • ResetMoving a branch pointer back, in soft, mixed or hard mode.
  • Force PushOverwriting remote history; use --force-with-lease and never on shared branches.
  • SquashCombining several commits into one.

Mid-level

Own a feature end to end without hand-holding.

Core: start here

  • Merge vs RebasePreserving history as it happened vs rewriting it to be linear.
12 more mid-level concepts

Senior

Own an app's architecture, performance, and failure modes.

  • Git InternalsBlobs, trees, commits and refs: what Git actually stores.
  • Patch FilesSharing changes as diff files instead of branches.
  • Monorepo vs PolyrepoOne repository for everything vs one per project.
  • WorktreeSeveral working directories checked out from one repository.