Advanced Operations

Interactive Rebase

git rebase -i HEAD~5        # edit last 5 commits
git rebase -i main          # edit all since diverging from main

Commands in editor:

pick = keep as-is
reword = edit message
squash = merge into previous, keep message
fixup = merge into previous, discard message
drop = remove commit

git rebase --continue       # after resolving conflicts
git rebase --abort          # cancel and restore
git rebase --skip           # skip problematic commit

Bisect (Find Bug)

git bisect start
git bisect bad              # current has bug
git bisect good v1.0.0      # known good version

# Git checks out middle commit. Test, then:
git bisect good             # no bug here
git bisect bad              # bug here
# Repeat until found

git bisect reset            # done, return to branch

Automated bisect:

git bisect start HEAD v1.0.0
git bisect run ./test-script.sh   # exit 0 = good, 1 = bad

Worktree (Parallel Work)

git worktree add ../hotfix hotfix-branch   # new dir with branch
git worktree add ../feature -b new-feature # create new branch
git worktree list                          # show all worktrees
git worktree remove ../hotfix              # clean up

Use cases:

Review PR while keeping current work
Run tests on main while developing
Compare behavior between versions

Reflog (Recovery)

git reflog                  # all HEAD movements
git reflog show branch      # specific branch history

Recovery patterns:

# After bad rebase
git reflog
git reset --hard HEAD@{5}   # go back 5 reflog entries

# Recover deleted branch
git reflog
git branch recovered commit-hash

# Recover dropped stash
git fsck --unreachable | grep commit

Sparse Checkout (Large Repos)

git sparse-checkout init --cone
git sparse-checkout set packages/my-app packages/shared
git sparse-checkout add packages/another
git sparse-checkout disable         # checkout everything again

Clone with sparse:

git clone --filter=blob:none --sparse URL
cd repo
git sparse-checkout set path/to/need

Subtree vs Submodule

Subtree (copies code into repo):

git subtree add --prefix=lib/shared URL main --squash
git subtree pull --prefix=lib/shared URL main --squash
git subtree push --prefix=lib/shared URL main

Submodule (pointer to commit):

git submodule add URL path
git submodule update --init --recursive
git submodule update --remote

Choose subtree for: simpler workflow, infrequent updates Choose submodule for: large deps, independent release cycles

Merge vs Rebase

Merge (preserves history):

git checkout main
git merge feature           # creates merge commit
git merge --no-ff feature   # always create merge commit

Rebase (linear history):

git checkout feature
git rebase main             # replay commits on top of main
git checkout main
git merge feature           # fast-forward

Rule: Rebase local unpublished commits. Never rebase published branches.

Conflict Resolution Tools

git mergetool               # launch configured tool
git checkout --ours file    # take current branch version
git checkout --theirs file  # take incoming version

See all versions:

git show :1:file            # common ancestor
git show :2:file            # ours
git show :3:file            # theirs

Rerere (Remember Resolution)

git config --global rerere.enabled true   # remember conflict resolutions
git rerere forget file                    # forget bad resolution

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