Git

Submodules embed one repo inside another by pinning a commit, not a branch. Knowing that single fact prevents most of the pain — detached HEADs, missed pushes, and silent divergence after a pull.

How the three dominant branching models differ in branch count, integration cadence, and release rhythm — and how to pick one based on your release model, not the model's brand.

Treat each commit (or tiny branch) as the unit of review, not a large feature branch. Smaller reviews, less waiting, better commit hygiene — and a non-trivial rebase tax to pay.

Local-only ignores, untracking already-tracked files, hiding local edits to tracked files, and a global ignore for OS junk — the four problems .gitignore alone doesn't solve.

Binary search across commit history to find the first bad commit. Works manually or fully automated with a script — turning a needle-in-a-haystack search into log2(n) steps.

Interactive rebase, soft reset, and merge --squash all collapse commits into fewer commits. They differ in granularity, on which branch they leave the result, and how much history they preserve.

What rebase actually does to your commits, how to drive the interactive form, and the recovery moves that keep a bad rebase from becoming a lost-work incident.

How and when to use git worktree to keep multiple branches checked out at once, sharing one object store, without the disk cost or coordination headaches of multiple clones.