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Git

tech/software engineering

Basics

  • Delete a branch. git branch -d branch_name
  • List all the branches. git branch
  • Switch to a branch git checkout branch_name
  • Git make the current branch exactly the same as upstream. git fetch upstream git reset --hard upstream/master git push -f origin [current_branch_name]
  • Delete a branch remotely git push origin --delete <branchName>
  • How to checkout a remote branch that doesn't exist locally?

git branch -v -a To see all the branches available for checkout. git fetch git checkout <branch_name> The branch name should not contain origin/ or remotes/.

  • How to deal with a detached HEAD?

It is caused by checking out a remote branch directly like git checkout origin/devel Or caused by checkout a commit with SHA1. It is starting a new route from a previous node (commit). So you need to create a branch to save the changes on the detached HEAD. Just use git checkout -b <branch_name> is good enough.

  • Show remote URL. git remote show origin
  • Show git branch tree-structure view. git status --graph
  • Stash by hunks. git stash -p and use ? to print the instructions.

Tags

List the tags 

git tag

Get pull the tags 

git fetch

Add a tag 

git tag -a tag_name
git push origin tag_name

Undo Things

  • How to undo a commit (not pushed to remote) to unstagged? git reset HEAD~
  • Unstage a single file git restore --staged my_file.py
  • How to revert the last several commits? First you can use git reset <SHA1> and git push origin <branch_name> -f. However, this is not recommended, since it lost the information of those commits in the commit history. You should use revert. If only revert one commit, just git revert <SHA>. This command will directly fire a new commit for you to reverse the changes. If multiple revert, use git revert -n <SHA> multiple times for different commits in the latest to the oldest order. -n means do not auto fire a commit for it. If the commit to be reverted is a merge commit, use git revert -n <SHA> -m 1 to revert to the 1st branch or -m 2 to revert to the second branch. Then make a commit. It can only revert the last changes, instead of jumping over some commits and revert the previous ones.
  • How to revert commits in the middle of the history? If we have commit A B C D E, and you want to revert B and C. You first git checkout -b <new_branch_name> <SHA of A>. Then cherry-pick the commits from D to E with git cherry-pick <SHA of D>..<SHA of E>.
  • how to delete a tag? git tag -d [tag_name] git push origin :[tag_name]
  • how to delete a release? click the release name. The delete button is on the top right.
  • How to stash? We stash the uncommited changes and pull from remote and unstash them to apply. git stash git stash pop

Clean Up

rebase master -i

Sync with Remote

Force push the local changes.

git push origin branch_name --force-with-lease

Force pull.

git checkout branch_name
git fetch --all
git reset --hard origin/branch_name

Across Branches

How to merge two branches?

You can use git merge but not recommended. git rebase is more professional. For example, you are rebasing the master branch when you are on a feature branch. It would start from the current master branch head, and add the commits of your feature branch one by one to it. So that in the log of the current branch (feature) the commits from master would before the commits of the feature branch. If there is a conflict, it would stop and ask you to solve. You just solve it and git add the files with conflicts. and no commit is needed just use git rebase --continue to continue the rebase process. When push to the remote branch, it needs to use git push --force-with-release origin branch_name .

How to cherry-pick?

Just find the commit in other branch you need. And on the branch you want to add the commit, execute git cherry-pick <SHA>.

Working on a branch with a dependence on another branch that is being reviewed

feature_b is created like this git checkout feature_a git checkout -b feature_b

update feature_b for the latest changes in feature_a git checkout feature_b git rebase feature_a

When feature_a has been merged into master, you simply get the new master and rebase feature_a onto it a last time: git checkout master git pull origin master git checkout feature_b git rebase --onto master feature_a feature_b

Checkout a pull request branch of other's fork

$ git remote add theirusername git@github.com:theirusername/reponame.git
$ git fetch theirusername
$ git checkout -b mynamefortheirbranch theirusername/theirbranch