Reflog and Git Hooks

Build the mental model

Reflog and hooks are both quietly powerful because they operate below the level of commits and branches: reflog tracks where HEAD has actually been, and hooks let scripts react automatically to what you are about to do.

The reflog is a local log of every place your HEAD and branch tips have pointed, including commits that no longer belong to any branch, like ones erased by a hard reset. Git keeps the commit object around, unreachable but intact, until garbage collection eventually cleans it up, usually after 30 to 90 days. Run git reflog, find the hash from before the mistake, and git reset --hard back to it.

Hooks are scripts Git runs automatically at defined points in its workflow, stored as executable files in .git/hooks, one file per trigger point. A pre-commit hook runs right before a commit is finalized, commonly used to lint or format changed files and reject the commit if checks fail. A commit-msg hook can enforce message conventions, and a pre-push hook can run a test suite before code ever leaves your machine.

Reflog

A local, chronological log of every position HEAD and branch tips have held, including commits no longer reachable from any branch.

Git Hook

An executable script Git runs automatically at a defined point in its workflow, such as pre-commit or pre-push.

REFLOG TIMELINE AND HOOK TRIGGER POINTS
---------------------------------------
REFLOG (local history of where HEAD has pointed)

HEAD@{2}   HEAD@{1}              HEAD@{0}
  A ------> B ------> (hard reset back to A)
            ^
            still exists, just orphaned from any
            branch -- recoverable via its hash

HOOKS (scripts triggered at points in the workflow)

edit files -> pre-commit -> commit -> pre-push -> push
              (lint/test)            (run tests)

Connect it to a real scenario

The reflog example commits a notes file twice, Add project notes then Add important analysis, then deliberately loses the second commit with git reset --hard HEAD~1. git log --oneline afterward shows only the first commit, as if the second never existed.

• Reflog is a local log of every position HEAD has held, including orphaned commits no branch points to anymore — it's how you recover from a bad reset.
• Reflog is not a backup: it's local-only, doesn't transfer with clones, and expires after roughly 30-90 days.
• Hooks are executable scripts in .git/hooks that run automatically at points like pre-commit, commit-msg, and pre-push, commonly used for linting, formatting, and tests.

Try the working example

export GIT_AUTHOR_NAME="Thuta Learner"
export GIT_AUTHOR_EMAIL="learner@example.com"
export GIT_COMMITTER_NAME="Thuta Learner"
export GIT_COMMITTER_EMAIL="learner@example.com"

git init -q -b main
export GIT_AUTHOR_DATE="2026-01-01T09:00:00"
export GIT_COMMITTER_DATE="2026-01-01T09:00:00"
echo "draft 1" > notes.txt
git add notes.txt
git commit -m "Add project notes"

export GIT_AUTHOR_DATE="2026-01-01T10:00:00"
export GIT_COMMITTER_DATE="2026-01-01T10:00:00"
echo "draft 2 - important work" > notes.txt
git add notes.txt
git commit -m "Add important analysis"
LOST_COMMIT=$(git rev-parse HEAD)

git log --oneline
git reset --hard HEAD~1
git log --oneline
git reflog

git reset --hard $LOST_COMMIT
git log --oneline

# --- hooks ---
printf "#!/bin/sh
echo \"Running pre-commit checks...\"
echo \"pre-commit hook: OK\"
" > .git/hooks/pre-commit
chmod +x .git/hooks/pre-commit

export GIT_AUTHOR_DATE="2026-01-01T11:00:00"
export GIT_COMMITTER_DATE="2026-01-01T11:00:00"
echo "more notes" >> notes.txt
git add notes.txt
git commit -m "Add more notes"

After the hard reset, git log --oneline shows only:

ea0d552 Add project notes

git reflog shows the full history, including the lost commit:

ea0d552 HEAD@{0}: reset: moving to HEAD~1
a628635 HEAD@{1}: commit: Add important analysis
ea0d552 HEAD@{2}: commit (initial): Add project notes

After git reset --hard a628635, git log --oneline shows both commits again:

a628635 Add important analysis
ea0d552 Add project notes

For the hook: committing with the pre-commit hook installed printed, before the commit completed:

Running pre-commit checks...
pre-commit hook: OK

Git - githooks Documentation — Git & GitHub