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Tagged “git”

Fixing Github Command Line Authentication Issues

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On at least two ocassions I’ve found myself scratching my head when an attempted push to a newly-created Github repo is met with authentication failures, despite me being sure I’m using the correct credentials.

Here’s the lowdown on the issue and how to resolve it.

Essentially the problem relates to Github expecting a personal access token rather than a password (although it provides no helpful hints that this is the case).

This might be because your Github account has 2FA enabled, and/or for security purposes because your account is part of an organisation that uses SAML single sign-on (SSO).

In my case, I had previously created a personal access token with the requisite privileges (in my Github account’s Developer Settings > Tokens section) for the purposes of API access, so I was able to just reuse that. However, if need be I could have created a new one.

Thanks to Ginny Fahs who had the same problem and documented her solution.

Github’s Help page Creating a personal access token for the command line is also useful.

Semantic Commit Messages

A link posted on in

A fairly rigid commit format (chore, fix, feat etc) which should lead to your git log being an easy-to-skim changelog.

I’d noticed that my git commit messages could benefit from greater consistency. So I’ve started adopting Sparkbox’s approach.

Here’s how to use the different commit types:

chore: add Oyster build script
docs: explain hat wobble
feat: add beta sequence
fix: remove broken confirmation message
refactor: share logic between 4d3d3d3 and flarhgunnstow
style: convert tabs to spaces
test: ensure Tayne retains clothing

My Git Cheatsheet

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I’ve used Git for many years but it can still trip me up. At times I’ve worked primarily in a GUI (like Sourcetree or Fork), and other times directly on the command line. I’ve worked on projects where I’ve been the sole developer and others where I’m part of a large team. Regardless of the tools or context, I’ve learned there are certain need-to-knows. Here’s a list of useful Git concepts and commands for my reference and yours.

Note: the following is not an exhaustive list but rather the thing I keep coming back to and/or regularly forget. For deeper explanations, see the list of resources at the foot of the article.

Table of contents

Starting work

Create a remotely-hosted repo

Option 1: Create a new repo in your Github account

This generates a new, empty repo (optionally initialised with a README).

Do this when you will be working on a new, dedicated project rather than contributing changes to a pre-existing one.

Option 2: Create repo from a “template repository” (owned by you or someone else)

This generates a new repo with the same directory structure and files as the template. It’s a good option for starting your own new, potentially long-lived project from a solid starting point.

Unlike a fork it does not include the entire commit history of the parent repository. Instead it starts with a single commit.

Github Reference: Creating a repository from a template

Option 3: Fork an existing repo (usually owned by someone else)

This generates a new repo which is a copy of another repo, including its commit history. Your commits will update your copy rather than the original repo.

Do this by clicking the Fork button in the header of a repository.

This is good for (often short-lived) collaboration on an existing repo. You can contribute code to someone else’s project, via PRs.

Github Reference: Working with forks

Start locally by cloning

clone creates a local copy on your computer of a remote (Github-hosted) repo.

cd projects
git clone https://github.com/githubusername/projectname.git optionallocaldirectoryname

You might be cloning a repo you own, or one owned by someone else (to use its features in your project).

Your local copy will, by default, have its origin remote set to the Github repo you cloned.

I cloned an empty new project

We’re in easy streets. The default remote is set exactly as you want it. Just write code, push at your leisure, and pull if/when you need to.

I cloned a pre-existing project (owned by me or someone else):
I plan to use it in my own, separate project

You might want to cut all ties and have a clean slate, git-wise.

rm -rf .git
git init
git remote add origin https://github.com/mygithubusername/mynewproject.git
git push -u origin master

Alternatively you might want to keep the original remote available so you can pull in its future project updates, but reset the origin remote to your new/target repo.

git remote rename origin upstream
git remote add origin https://github.com/mygithubusername/mynewproject.git
git push origin master
git pull origin master
# in the future the original repo gets an update
git pull upstream master
The source repo is my fork of a project to which I want to contribute

See Working with forks for how best to stay in sync and open PRs.

Duplicating (also knows as “duplicate without forking”)

This is a special type of clone. I know this is an option, but it‘s not one I’m familiar with or have had call to use. I can refer to Duplicating a repository if need be.

Start locally from a blank slate

Although cloning is the easiest way to get started locally, ocassionally I start by coding from scratch instead.

mkdir myproject && cd myproject
echo "# Welcome to My Project Repo" >> README.md
git init
git add README.md
git commit -m "first commit"

# go to Github and create an empty repo, if you haven’t already.
# then add as a remote
git remote add origin https://github.com/mygitusername/myproject.git

# push up, passing -u to set the remote branch as the default upstream branch our local branch will track
# this saves typing out ‘origin master’ repeatedly in future.
git push -u origin master

Remotes

Remove a remote from your local settings:

git remote rm <name>

Rename a remote:

git remote rename oldname newname

Configuration

Configure your favourite editor to be used for commit messages:

git config --global core.editor "nano"

Use git st as a shortcut for git status (to stop me mistyping as “statsu”):

git config --global alias.st status

Configure any setting:

git config [--global] <key> <value>

git config --global user.email "myname@domain.com"

Staging, unstaging and deleting files

# stage all unstaged files
git add .

# stage individual file/s
git add filename.txt

Unstage with reset (the opposite of git add):

# unstage all staged files
git reset .

# unstage individual file/s
git reset filename.txt

Delete a physical file and stage the deletion for the next commit:

git rm folder/filename.txt

Committing updates

Commit with a multi-line message:

git commit

Commit with short message:

git commit -m "fix: typo in heading"

Stage and commit all changes in a single command (note: doesn’t work with new, untracked files):

git commit -am "fix: typo in heading"

Branches

Show all local branches:

git branch

Show all local and remote branches:

git branch -a

Show branches you last worked on (most recently commited to):

git branch --sort=-committerdate

Save current state to new branch but don’t yet switch to it (useful after committing to wrong branch):

git branch newbranchname

Create and switch to new branch (main or whatever branch you want to branch off):

git checkout -b mynewbranch

Note that if you branch off foo_feature then when creating a PR in GitHub for your changes in mynewbranch you can change the Base branch from the default of main to foo_feature. This specifies that you are requesting your changes be merged into foo_feature rather than main and makes the comparison of changes relative to foo_feature rather than main.

Switch to an existing branch:

git checkout branchname

Save typing by setting the upstream remote branch for your local branch:

# git branch -u remotename/branchname
git branch -u fuzzylogic/v3

# now there’s no need to type origin master
git pull

Delete local branch:

git branch -d name_of_branch

# need to force it because of some merge issue or similar?
git branch -D name_of_branch

Save changes temporarily

stash is like a clipboard for git.

# Before changing branch, save changes you’re not ready to commit
git stash

# change branch, do other stuff. Then when return:
git stash pop

Staying current and compatible

fetch remote branch and merge simultaneously:

git pull remotename branchname

# common use case is to update our local copy of master
git pull origin master

# shorthand when a default upstream branch has been set
git pull

# an alternative is to update (fetch) which does not auto-merge, then 'reset' to the latest commit on the remote
# https://stackoverflow.com/questions/55731891/effects-of-git-remote-update-origin-prune-on-local-changes
git checkout master
git remote update --prune
git reset --hard origin/master

Merge another branch (e.g. master) into current branch:

git merge otherbranch

# a common requirement is to merge in master
git merge master

Rebasing

git rebase can be used as:

  1. an alternative to merge; and
  2. a means of tidying up our recent commits.

As an alternative to merge its main pro is that it leads to a more linear therefore easier-to-read history. Note however that it is potentially more disruptive therefore not right for every situation.

Say I’ve been working on a feature branch and I think it’s ready.

I might want to just tidy up my feature branch’s commits and can do this with an “interactive rebase”. This technique allows me to tidy my feature branch work to remove trivial, exploratory and generally less relevant commits so as to keep the commit history clean.

I might also want to bring in master to ensure synchronicity and compatibility. rebase sets the head of my feature branch to the head of master then adds my feature branch’s commits on top.

While it’s a good idea to rebase before making a PR, don’t use it after making a PR because from that point on the branch is public and rebasing a public branch can cause problems for collaborators on the branch. (The only exception to the previous rule is if you’re likely to be the only person working on the PR branch)

Rebuild your feature branch’s changes on top of master:

git checkout master
git pull origin master
git checkout myfeaturebranch
git rebase master

Force push your rebased branch (again, only when you’re unlikely to have/require collaborators on the PR):

git push --force origin myfeaturebranch

Tidy a feature branch before making a PR:

git checkout myfeaturebranch
git rebase -i master

# just tidy the last few (e.g. 3) commits
git rebase -i HEAD~3

# this opens a text editor listing all commits due to be moved, e.g.:
pick 33d5b7a Message for commit #1
pick 9480b3d Message for commit #2
pick 5c67e61 Message for commit #3

# change 'pick' to 'fixup' to condense commits, say if #2 was just a small fix to #1
pick 33d5b7a Message for commit #1
fixup 9480b3d Message for commit #2
pick 5c67e61 Message for commit #3

# alternatively if use 'squash', after saving it will open an editor
# and prompt you to set a new commit message for the combined stuff.
pick 33d5b7a Message for commit #1
squash 9480b3d Message for commit #2
squash 5c67e61 Message for commit #3

More on squash including a handly little video if I forget how it works.

Undo a rebase:

git reset --hard ORIG_HEAD

For more detail, read Atlassian’s guide to rebasing.

Reviewing your activity

Show commit history (most recent first; q to quit):

git log

# compact version
git log --oneline

# limit scope to commits on a branch
git log branchname

Check if your feature branch is trailing behind:

# show commits in master that are not yet in my feature branch
git log --oneline my-feature..master

# show commits on remote branch that are not yet in my local branch
git log --pretty='format:%h - %an: %s' new-homepage..origin/new-homepage

# show commits by me that included “heroku” and that changed file Gemfile
git log --author=Demaree --grep=heroku --oneline Gemfile

Show changes that occurred in the most recent commit or a given commit.

git show

# show changes in a given commit
git show 591672e

Review differences between staged changes and last commit:

git diff --cached

Review changes between a given version/commit and the latest:

git diff 591672e..master

Fixing Things

Discard all your as-yet uncommitted changes:

git restore .

Get your local feature branch out of a problem state by resetting to the state it is on the remote (e.g. at last push).

git reset --hard origin/my-branch

Undo all the changes in a given commit:

git revert 591672e

Alter the previous commit (change the message and/or include further updates):

# we are amending the previous commit rather than creating a new commit.
# if file changes are staged, it amends previous commit to include those.
# if there are no staged changes, it lets us amend the previous commit’s message only.
git commit --amend

Move current branch tip backward to a given commit, reset the staging area to match, but leave the working directory alone:

git reset 591672e

# additionally reset the working directory to match the given commit
git reset --hard 591672e

See what the app/site was like (e.g. whether things worked or were broken) at a given previous commit, noting the following:

  • You’re now “detatched”, in that your computer’s HEAD is pointing at a commit rather than a branch.
  • You’re expected to merely review, not to make commits. Any commits you make would be “homeless”, since commits are supposed to go in branches. (However you could then branch off.)
git checkout 591672e

Return one or more files to the state they were in at a previous commit, without reverting everything else.

git checkout 3aa647dac9a8a251ca223a693d4c140fd3c1db11 /path/to/file.md /path/to/file2.erb

# if happy you then need to commit those changes
git commit

When git st reveals a list of staged files including lots of strange files you don’t want there mixed with others you do…

# add those you want to stay modified and staged
git add path/to/file-I-want-1.rb path/to/file-I-want-2.md

# this will clear all others out of the stage
git checkout .

Grab one or more commits from elsewhere and drop into your current branch:

git cherry-pick 591672e

# grab the last commit from a branch e.g. master
git cherry-pick master

Fix a pull that went wrong / shouldn’t have been done:

git pull origin branchname
# whoops!

git reflog
# shows a list of every thing you've
# done in git, across all branches!
# each one has an index HEAD@{index}
# find the one before you broke everything

git reset HEAD@{index}
# magic time machine

Miscellaneous handy things

Revert to the previous branch you were on

git checkout -

Useful GitHub stuff

Useful external resources

See all tags.