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Git

Source code mirror: https://github.com/git/git

Git tips -https://github.com/git-tips/tips

Quickly rewrite git repository history (filter-branch replacement) - https://github.com/newren/git-filter-repo

Ask HN: Apps that are built with Git as the back end? - https://news.ycombinator.com/item?id=33261862

https://github.com/github/git-sizer. Compute various size metrics for a Git repository, flagging those that might cause problems. This tools is referenced in https://docs.github.com/en/repositories/working-with-files/managing-large-files/about-large-files-on-github.

Branch models​

Trunk Based Development - https://trunkbaseddevelopment.com

git-flow - https://nvie.com/posts/a-successful-git-branching-model

GitHub flow - https://docs.github.com/en/get-started/quickstart/github-flow

Upstream branch​

Important: 'upstream' is about branches, not repositories - see this.

Documentation of git push -u: https://git-scm.com/docs/git-push#Documentation/git-push.txt--u

git push -u origin main
git push --set-upstream origin main

To avoid having to do this we can set autoSetupRemote to true:

# Set value
git config --global push.autoSetupRemote true
git config --global --add --bool push.autoSetupRemote true

# Get value
git config --global push.autoSetupRemote

See https://twitter.com/JI/status/1546948817462800384 and https://stackoverflow.com/a/72401899/4034572.

Clone a single branch only​

This can be used for exampe to build a Docker container on some specific branch, in order to avoid fetching all the other -unnecessary- branches.

git clone git@github.com:SomeOrg/some-repository.git --branch branch_name --single-branch <local-folder>

https://stackoverflow.com/questions/1778088/how-do-i-clone-a-single-branch-in-git

https://stackoverflow.com/questions/1911109/how-do-i-clone-a-specific-git-branch

--[no-]single-branch docs: https://www.git-scm.com/docs/git-clone#Documentation/git-clone.txt---no-single-branch

Undo last commit​

If not pushed yet:

# Keep changes
git reset --soft HEAD^

# Discard changes
# WARNING: THIS ALSO DISCARDS ANY CHANGES ON TRACKED FILES!
# TO AVOID LOOSING CHANGES DO 'git stash push' BEFORE
git reset --hard HEAD^

source

On a public commit:

git revert HEAD

Also see: git undo: We can do better

Undo merge (eg if we commit on the main branch by mistake)​

If not pushed yet:

# WARNING: THIS ALSO DISCARDS ANY CHANGES ON TRACKED FILES!
# TO AVOID LOOSING CHANGES DO 'git stash push' BEFORE
git reset --hard HEAD^

https://stackoverflow.com/questions/5623162/undo-last-commit-merge

If pushed:

https://www.git-tower.com/learn/git/faq/undo-git-merge/

https://stackoverflow.com/questions/12534312/revert-a-merge-after-being-pushed

Revert the changes done on a file (or files) in a branch, so that it's content is the same as develop or master​

git checkout <branch> -- <filename>

Eg: git checkout develop -- buildsystem/versions.gradle

This leaves in the staging area the changes that bring the file to the same contents as develop. You need to commit then.

Note that you can put as many files as you want: git checkout <branch> -- <filename> ... <filename>.

You can also specify an entire folder: git checkout main -- config/sync.

And you can specify a file extension in a folder: git checkout main -- seed_data/*.json

source1 source2

Merge changes from remote master branch to a feature branch without switching to master​

git checkout some-branch
git fetch origin # gets you up to date with origin by getting all commits on all branches, but named 'origin/branch'
git merge origin/master # brings all commits in 'origin/master' to whatever branch we are; we could use --ff-only
git fetch origin master:master # update master if we have a feature branch checked out
git fetch origin && git merge origin/main && git fetch origin main:main

Note that this fetches all branches. To avoid this do:

git fetch origin main:main && git merge origin/main

source-part-1 source-part-2

GitHub pull request​

https://gist.github.com/Chaser324/ce0505fbed06b947d962

http://blog.davidecoppola.com/2016/11/howto-contribute-to-open-source-project-on-github/

git remote add upstream git@github.com:Kotlin/kotlinx.coroutines.git

Incorporating upstream changes​

git fetch upstream master
git log --oneline --graph --decorate --all
git checkout master
git merge upstream/master
git push origin master

error: pathspec 'some-remote-branch' did not match any file(s) known to git​

When trying to checkout a remote branch (eg when reviewing a pull request), sometimes we get the error "error: pathspec 'some-remote-branch' did not match any file(s) known to git".

To fix it run git fetch --all.

More info: https://stackoverflow.com/questions/30800454/error-pathspec-test-branch-did-not-match-any-files-known-to-git

Rebase​

Rewriting History - https://git-scm.com/book/en/v2/Git-Tools-Rewriting-History

Squash, Merge, or Rebase? https://matt-rickard.com/squash-merge-or-rebase

Rebase Considered Harmful: https://www.fossil-scm.org/home/doc/trunk/www/rebaseharm.md - See discussion on HN

Golden Rule of Rebasing​

The golden rule of git rebase is to never use it on public branches.

https://www.atlassian.com/git/tutorials/merging-vs-rebasing#the-golden-rule-of-rebasing

--update-refs​

https://github.blog/2022-10-03-highlights-from-git-2-38/#rebase-dependent-branches-with-update-refs - https://news.ycombinator.com/item?id=33071275

Rebase interactive​

TODO check for interactive rebase https://github.com/jesseduffield/lazygit

https://git-scm.com/docs/git-rebase

git rebase -i <commit you want to amend>^
# or with the alias
grbi <commit you want to amend>^

r or reword - amend commit message (note that if we are only rewording we don't need to do any of the following commands, just save the new commit message and we are done)

gc! (git commit --amend)
grbc (git rebase --continue)

e or edit - modify commit

// edit file(s)...
gaa (or) ga some/file.txt
gc! (git commit --amend)
# it's also possible to do just do gcan!, or gaa and then gcn!
grbc (git rebase --continue)

Rebase until first (root) commit​

git rebase -i --root

Amend​

https://git-scm.com/docs/git-commit

-a/--all: Automatically stage files that have been modified and deleted, but new files you have not told Git about are not affected

--no-edit: Use the selected commit message without launching an editor. For example, git commit --amend --no-edit amends a commit without changing its commit message.

alias | grep amend:

'gc!'='git commit -v --amend'
'gcn!'='git commit -v --no-edit --amend'

'gca!'='git commit -v -a --amend'
'gcan!'='git commit -v -a --no-edit --amend'

Amend undo​

https://stackoverflow.com/questions/1459150/how-to-undo-git-commit-amend-done-instead-of-git-commit

Fix conflict 'both added'​

https://stackoverflow.com/questions/9823692/resolving-a-both-added-merge-conflict-in-git

Estic a una branca i faig merge de dev a la meva branca. Si vull lo de dev faig:

git checkout --theirs <filename>
git add <filename>

I si vull lo de la meva branca:

git checkout --ours <filename>
git add <filename>

Nota: pel <filename> es pot fer servir * per seleccionar varis fitxers alhora, i també pot ser una carpeta.

Overwrite/reset local branch like remote branch​

danger

This will discard any changes on tracked files! To avoid loosing changes do git stash push before.

git reset --hard @{u}

or

git fetch origin
git reset --hard origin/mybranch

source1, source2

Remove untracked files​

git clean -f -d

Prune​

git remote prune origin

Ensure merge without merge commit with --ff-only​

From the docs:

--ff is the default...

With --ff, when possible resolve the merge as a fast-forward (only update the branch pointer to match the merged branch; do not create a merge commit). When not possible (when the merged-in history is not a descendant of the current history), create a merge commit.

With --ff-only, resolve the merge as a fast-forward when possible. When not possible, refuse to merge and exit with a non-zero status.

git checkout -b feature-branch

# make some commits

git rebase main
git checkout main
git merge --ff-only feature-branch

source

--ff-only docs

See commit and code differences between two branches​

# commits
git log main..feature-branch
# code
git diff main..feature-branch
# code for specific file, if we are on the feature-branch
git diff main.. path/to/file.ts
# files changed
git diff --name-status main..feature-branch

Note that you can have 3 dots (...). And if you've already switched to feature-branch you can use git log main...

See source

Squash all commits on a branch​

Can be used to split a big pull request into various PR by creating several commits.

git checkout your-branch
git reset $(git merge-base master-or-develop your-branch-name)

This leaves all changes on the branch at the staging area. Then you can git add . and git commit.

source

Tags​

View: git show 2.4.0

Delete local tag: git tag -d 2.4.0

Delete remote tag: git push -d origin 2.4.0

Push single tag: git push origin <tag_name>

Push all tags (warning: should not be used generally, see why in this comment): git push -–tags or git push origin --tags

Always use annotated tags​

git tag -a v1.0

They have extra information like author, date, SHA and message (more info).

Remove carriage return​

If you see ^M run sed -i.bak $'s/\r//' filename (with backup) or sed -i '' -e $'s/\r//' filename (no backup).

source

Change commit email​

Start by setting the new email either on the global config or the repository (local) config:

git config --global user.email new@email.com
git config --local user.email new@email.com

Then get the SHA of the previous commit of the commit with the wrong email.

Run this command (source):

git -c rebase.instructionFormat='%s%nexec GIT_COMMITTER_DATE="%cD" GIT_AUTHOR_DATE="%aD" git commit --amend --no-edit --reset-author' rebase -f <previous commit SHA, or --root for all commits>

Note that this keeps both the AuthorDate and CommitDate unchanged, which is what makes sense. Other solutions set the date of all the modified commits to the current date, which is nonsense since you end up with dozens of commits with the same date, and you loose all the date history. The SHA of the commits will of course change though, since we are rebasing.

Another way to do it​

Alternatively, you can also do it like this, but it requires running 2 commands (source):

git rebase -r <previous commit SHA> --exec "git commit --amend --no-edit --author 'Albert Vila Calvo <new@emailcom>'"

After this commit, if you run git log --pretty=fuller you'll get a wrong CommitDate (set to the current date, instead of the original):

Author:     Albert Vila Calvo <my@email.com>
AuthorDate: Sun May 5 21:59:28 2024 +0200
Commit:     Albert Vila Calvo <my@email.com>
CommitDate: Sun Jun 2 14:07:23 2024 +0200

To fix it run:

git rebase --committer-date-is-author-date <previous commit SHA>

This changes the SHA of the commits again.

Branch name​

Set the default branch name for new repositories​

git config --global init.defaultBranch <name>

Rename local branch only​

git branch (-m | -M) [<oldbranch>] <newbranch>

Eg to rename master to main:

  • If you are in master: git branch -m main.
  • If you are not in master git branch -m master main.

Rename local and remote branch​

# Rename:
git branch -m new-name # if we are on the branch
git branch -m old-name new-name # if we are not

# Delete the old-name remote branch and push the new-name local branch:
git push origin :old-name new-name

source and more info

Fix error​

When doing git push origin :master main sometimes we get this error:

 ! [remote rejected] master (refusing to delete the current branch: refs/heads/master)
error: failed to push some refs to 'github.com:AlbertVilaCalvo/JavaScript-Udacity-Memory-Game.git'

This happens when eg we are renaming the branch master to main on a GitHub/Bitbucket repository that has master set as the default branch. To fix this, go to the GitHub website → navigate to the repository → Settings tab → Branches, and change the 'Default branch'. After doing this, try again and it will work. (On Bitbucket, to change the default branch go to the repository → Repository settings → Repository details tab, expand the ADVANCED section and change 'Main branch'.)

Prevent commiting on main/master branch by mistake​

Add this .git/hooks/pre-commit.

#!/bin/sh

branch="$(git rev-parse --abbrev-ref HEAD)"

if [ "$branch" = "main" ]; then
  echo "You can't commit directly to main branch"
  exit 1
fi

Then make it executable with chmod +x .git/hooks/pre-commit.

From https://stackoverflow.com/questions/40462111/prevent-commits-in-master-branch and https://stackoverflow.com/questions/17293938/prevent-commits-in-a-local-branch.

Merge 2 git repositories​

From https://stackoverflow.com/a/10548919/4034572

Merge project-A into project-B.

cd /path/to/project-B
git fetch /path/to/project-A main
git merge --allow-unrelated-histories FETCH_HEAD

Seguint aquest post: https://stackoverflow.com/a/10548919/4034572. Commands:

git remote add backblaze ../Backblaze_exclusion_rule
git fetch backblaze --tags
git merge --allow-unrelated-histories backblaze/main

Be careful with conflicts! Eg if both projects have a README.md, it's better to re-name one of them first (do commit), otherwise you'll have to deal with conflicts.

To put project-A into a subfolder of project-B in a simple way, before running the commands above, first create a folder inside project-B, move all the files there, and then commit. Afterwards run the commands above.

--allow-unrelated-histories documentation: https://git-scm.com/docs/git-merge#Documentation/git-merge.txt---allow-unrelated-histories

More info:

Ignore mass reformatting with --ignore-rev and git config blame.ignoreRevsFile​

https://news.ycombinator.com/item?id=27643608

https://akrabat.com/ignoring-revisions-with-git-blame/

Config​

git config REFERENCE - https://git-scm.com/docs/git-config

Customizing Git - Git Configuration - https://git-scm.com/book/en/v2/Customizing-Git-Git-Configuration

Git Commands - Setup and Config - https://git-scm.com/book/en/v2/Appendix-C%3A-Git-Commands-Setup-and-Config

There are 3 type of settings:

Locationgit config option
System-wide (applies to every user)/etc/gitconfig--system
User-specific~/.gitconfig--global
Repo-specific.git/config--local

Show global config:

git config --list
git config -l
less ~/.gitconfig
bat ~/.gitconfig
~/.gitconfig
[core]
        editor = emacs -nw
[user]
        name = Albert Vila Calvo
        email = my@email.com
[init]
        defaultBranch = main

First time setup​

Getting Started - First-Time Git Setup - https://git-scm.com/book/en/v2/Getting-Started-First-Time-Git-Setup

git config --global user.name "Albert Vila Calvo"
git config --global user.email my@email.com
git config --global core.editor "emacs -nw"
git config --global init.defaultBranch main
git config --global push.autoSetupRemote true

Change email on a specific repo only​

Useful if you are using your personal computer for work or vice versa.

git config --local user.email my@email.com

Change colors​

All the things that can be customized are listed at https://git-scm.com/docs/git-config. Search for eg "color.diff".

Accepted color values: https://git-scm.com/docs/git-config#Documentation/git-config.txt-color

You can give it numbers, from 0 to 255, using the ANSI 256-color mode. Tip: test the color with echo $(git config --get-color "" "120 bold reverse") color test $(git config --get-color "" reset) (source).

Default color values: https://shallowsky.com/blog/programming/gitcolors.html

diff​

Available slots:

[color "diff"]
    meta = blue

Diff customization​

Commit message format​

Conventional Commits: https://www.conventionalcommits.org

Semantic Commit Messages: https://sparkbox.com/foundry/semantic_commit_messages

https://github.com/conventional-changelog/commitlint

Extra info:

Shell script execution permissions​

Make a shell script executable when you pull a repository.

https://stackoverflow.com/questions/40978921/how-to-add-chmod-permissions-to-file-in-git

Note: after running git update-index --chmod=+x path/to/file, then you need to commit.

After making the file executable, when doing git ls-files --stage it should have 100755.

.gitignore​

https://github.com/github/gitignore - A collection of useful .gitignore templates

https://git-scm.com/docs/gitignore

To match a directory only (but not files) add a slash at the end, eg build/. If there is a separator at the end of the pattern then the pattern will only match directories, otherwise the pattern can match both files and directories (source). You can also do /build if the directory is at the same level of the .gitignore, see https://github.com/github/gitignore/blob/main/Elixir.gitignore

CLI​

https://github.com/scmbreeze/scm_breeze

https://github.com/extrawurst/gitui

https://github.com/jesseduffield/lazygit

https://github.com/jonas/tig