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Notes on Advanced Git Workflows

The following is a list of notes on git/GitHub workflow tasks that I don't do often enough to remember implicitly.

Working with Forks and upstream repos

Keeping the name as something like upstream is probably a best practice

git remote -v
git remote add upstream <path to upstream repo>

Workflow for syncing an upstream fork

git checkout <local branch name>
git fetch upstream <branch name>
git merge upstream/<branch name>

NOTE: Be mindful here if you are working with multiple local and upstream branches, ie master and future. For example, it's really easy to accidentally merge upstream future into local master.

Gets a list of file names only that are different between the branches

git diff upstream/master origin/master --name-only

Get just a single file out of an upstream repo:

git checkout upstream/future -- docs/breaking_changes.md

Working with Patches

git diff > my.patch

OR:

git diff upstream/master origin/master > my.patch
git apply my.patch

Often useful when there are conflicting changes you want to ignore:

git apply --reject --whitespace=fix my.patch

Scorch the earth in a forked repo and reset it to match the remote again:

git reset --hard upstream/<branch name> git push origin <branch name> --force

  • This is extremely dangerous and the potential for loss of work is high. Plan ahead before running this command.

Rebasing a remote master to make it look like a new repo:

  1. Make sure you have merged the origin/upstream master and have a clean working directory.
  2. If you are planning to rewrite a GitHub repo, it is also recommended you make a fresh clone of it into a different directory for verification and recovery purposes.
  3. Run:
git rebase --interactive --root

NOTE: Using the --root arg is a big time saver if you want to rebase all history. Otherwise, you must pass in args to pick and choose as needed.

  1. As you cycle through the list of commits, pick the ones you want to squash, typically all of them but the top.
    You might need to resolve merge conflicts with git add and git rebase --continue.

NOTE: A rebase replays the list of commits over the current working branch, so the theirs and ours are flipped, so in the case of a rebase, ours means the master. If you want to try to skip merge conflicts, you can try:

git rebase --interactive --root -X ours master

NOTE: git commit --amend is handy here if you just want to rewrite the last commit message instead of re-running rebase.

  1. Once the local history looks the way that you want it to (use git logs to check it), it's time for the most dangerous step. You should hopefully have a backup copy that you made in step #2, and please don't get in the habit of using --force. This will take your local commit history and overwrite the GitHub repository's history to match. Then, once others subsequently do a git pull, their version lineage will be rewritten to match it.
git push --force
  1. Verification (optional). Go to the backup of the repository you made in step #2, and remember not to get latest. Then simply do a git diff origin to confirm that the rewritten history matches the previous contents of the repo.

resolve merge conflicts by accept theirs:

git checkout --theirs -- <filename>

Other ways Ways to squash commits

git reset --soft HEAD~3 && git commit --edit -m'blah' && git push --force

Where 3 is the number of commits back in history to squash.

Using GPG to sign commits

  • Install GPG using brew install gpg or similar based on your OS.
  • Add an alias to your .gitconfig file that associates git ci to commit -S
  • Add the following git configuration: git config --global user.signingkey where signingkey is the public key signature of the GPG key.

Other notes

Configure git to store GitHub creds in local OS store git config --global credential.helper store

GPG helpers

These are GPG commands that I rarely if ever need to run and therefore often forget. In order to import a GPG key from one machine to the other, simply run:

gpg --import <path.to.private>.key

In order to change the passphrase of a private key:

gpg --edit-key <key-id>
passwd
# ...
save

In order to list the currently installed keys:

gpg --list-keys