[2023 kcdc] rescuing your git repo using amend, reset, revert, rebase, bisect and cherry picking

Speaker: Brian Gorman

Twitter @blgorman

Repo with all commands

For more, see the table of contents.

Note: The GitHub repo is excellent and has all the instructions/commands. I did not try to recreate them in my blog. Instead I focused on the concepts

Branching strategies

  • Git Flow – main > dev > feature > developer. Good if just starting out. Not doing a lot of rebasing
  • Trunk based – no long running branches, frequent checkins. More popular due to CICD
  • Forking – integration repo, lieutenants and dictators. Good in super large orgs. More advanced
  • While branching strategy doesn’t matter, does matter if linear commit history. (Some operations are trickier if non-linear)

Rebase and Force Push

  • Rebase locally (based on remote or local branch)
  • Can have orphaned commits
  • Force pushing with a lease makes it safer
  • May have to deal with conflicts on a rebase
  • Use pull request; don’t create an extra merge commit
  • Important to delete old branches to avoid confusion

Finding lost commits

  • Can use GitViz (on WIndows only?) to look at graphically – https://github.com/Readify/GitViz
  • git reflog –all
  • git checkout <id> – puts in detached HEAD state to look at it. See double parens around commit id.

Clear local cache

  • Unlikely to need. Cleans up state
  • git reflog expire –expire-unreachable-now –all – expire all commits now
  • git gc –prune – run garbage collection

Removing feature

  • Not a problem if use feature flags
  • Create a branch to keep safe the parts not changing
  • Reset branch to last commit want to keep
  • Create new feature branch and pick commits want

Accidentally committed to main

  • Stop build as quickly as possible
  • Let team know not to change or pull from main
  • Create feature branch and cherry pick commits want
  • Reset main hard. git push –force-with-lease
  • Revert change to keep history
  • Change settings on repo so can’t commit to main again :).
  • (if can’t do this, can revert instead of changing history)

Someone committed a secret

  • If only a local commit, delete .git and start over. If already pushed…
  • If don’t need history, create new repo without history. If can’t….
  • Stop all dev as doing massive history update
  • Ensure all code checked in
  • Use git bisect to find the first commit containing the secret (start, good id, bad id, then you keep saying if a commit is good/bad). Alternatively git log -S “secret” gives you the commit
  • Ensure no branches are dependent on commit after the last good commit
  • Amend commit with one that doesn’t have the secret, Then cherry pick the rest
  • Everyone has to get the repo again since commits have changed

My take

I really like the mix of concepts, visualizations and videos of actually using the functionality. Great session.

One thought on “[2023 kcdc] rescuing your git repo using amend, reset, revert, rebase, bisect and cherry picking

  1. Thank you for the kind words and the awesome summary! I’m glad you enjoyed the session!

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