Git Reset Mechanics

Git Reset Mechanics

Three trees: HEAD (last commit), Index (staged), Working (disk). reset walks them in order and stops by flag.

Reset vs Checkout (no path)

• git reset --hard <ref> moves the branch HEAD points to; overwrites workdir without checking.
• git checkout <ref> moves HEAD (detaches if a commit); refuses if unsaved changes conflict.

With a Path

git reset <commit> -- <path> copies commit→index, skips HEAD move (can't partially move a pointer). --hard with a path is rejected.

git checkout <commit> -- <path> copies commit→index and workdir — destructive. Prefer modern restore:

• git restore --staged <path> — unstage
• git restore <path> — discard workdir change
• git restore --source=<ref> -SW <path> — both

Patterns

git reset --soft HEAD~            # undo commit, keep staging
git reset HEAD~                   # undo commit + unstage
git reset --hard HEAD~            # undo + discard (destructive)
git reset --soft HEAD~3 && git commit   # squash last 3
git reset --patch                 # unstage hunks

Pitfalls

• --hard is the only destructive common flag — no prompt. Recovery: git reflog → git reset --hard HEAD@{1}.
• Reset on a pushed branch rewrites history others have. Use revert instead.