Git

initial setup

mac

## base config
MAIL_ADDRESS="jan.weyrich@example.de"
git config --global user.name "Jan Weyrich"
git config --global user.email "$MAIL_ADDRESS"

## alias
git config --global alias.co checkout
git config --global alias.br branch
git config --global alias.ci commit
git config --global alias.st status

## generate ssh key
ssh-keygen -t rsa -b 4096 -C "$MAIL_ADDRESS"

# add ssh key agent for passwort prompt
# see https://docs.github.com/en/authentication/connecting-to-github-with-ssh/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent#adding-your-ssh-key-to-the-ssh-agent

## gpg
brew install gpg2 gnupg pinentry-mac

gpg --full-generate-key

# config for git
gpg -K --keyid-format SHORT
export GPG_SEC_ID=8627004B
gpg --armor --export $GPG_SEC_ID > ~/gpg-public.pem
git config --global user.signingkey $GPG_SEC_ID
git config --global gpg.program $(which gpg)
git config --global commit.gpgsign true
echo 'export GPG_TTY=$(tty)' >> ~/.zshrc
source ~/.zshrc

# for pw prompt see here: https://unixb0y.de/blog/articles/2019-01/gpg-password-macos-keychain
echo 'use-agent' > ~/.gnupg/gpg.conf
echo "pinentry-program /opt/homebrew/bin/pinentry-mac" > ~/.gnupg/gpg-agent.conf
gpgconf --kill gpg-agent


# check with
echo "test" | gpg --clearsign

# if you got: gpg: signing failed: No pinentry
# you may want to try with:
echo "/opt/homebrew/bin/pinentry" > ~/.gnupg/gpg-agent.conf
gpgconf --kill gpg-agent

## save passphrase for twelve hours
echo "default-cache-ttl 43200" >> ~/.gnupg/gpg-agent.conf

linux

# config
export MAIL_ADDRESS="jan.weyrich@example.de"
git config --global user.name "Jan Weyrich"
git config --global user.email "$MAIL_ADDRESS"

# alias
git config --global alias.co checkout
git config --global alias.br branch
git config --global alias.ci commit
git config --global alias.st status

# ssh
ssh-keygen -t rsa -b 4096 -C "$MAIL_ADDRESS"
echo 'eval `ssh-agent -s`' >> ~/.bashrc && source ~/.bashrc
ssh-add ~/.ssh/*_rsa

# gpg

gpg --full-generate-key
gpg --armor --export 7C37CF3A > ~/gpg-public.pem
git config --global gpg.program $(which gpg)
git config --global commit.gpgsign true

## save passphrase for twelve hours
echo "default-cache-ttl 43200" > ~/.gnupg/gpg-agent.conf


## view ssh pub key
cat ~/.ssh/id_rsa.pub
## view gpg pub key
gpg --armor --export 7C37CF3A > ~/gpg-public.pem

https and password manager

windows

# check existing methods
git help -a | grep credential

# there options might be available 
## credential           Retrieve and store user 
## credential-cache     Helper to temporarily store passwords in memory
## credential-store     Helper to store credentials on disk in plaintext (~/.git-credentials)

# credential-cache
git config --global credential.helper "cache --timeout 30000"

# credential-store 
git config --global credential.helper "store"

# you might need to install manager-core to use it
# and then set it via
# git config --global credential.helper "manager-core"

Workaround if no credential manager works (in windows probably):

git config --global credential.helper manager stores the credentials in plain text file ~/.git-credentials the next time you log in. The format in the file is like this: https://user:password@git.example.de. It only works, when using https. Sometimes the password is not saved after the frist prompt, in this case you can add the following to ~/.gitconfig:

[credential "https://git.example.de"]
 provider = generic

configure output behavior (disable pager)

git config --global pager.branch false

see here

wording

• Good references
• Usage of index explained
• index = staging area
• working tree = working directory
• (branch) head: pointer to the newest commit on a branch
• tag: fixed pointer to commit
• HEAD: movable pointer which usually points to the head/tip of a branch. The next commit will take action on the commit which HEAD points to.
• reset (HEAD vs index vs working tree)
• Reset Soft (HEAD only)
• Mixed (Head and index)
• Hard (Head, index, Working Tree)

clear working directory (with untracked files)

With reset:

• To last commit including ignored files: git reset --hard && git clean -dfx
• To last commit: git reset --hard && git clean -df

With stash. Allows to revert changes, but not recommended with many files:

• To last commit including ignored files: git stash --all
• To last commit: git stash --include-untracked
• Permanently deleting files: git stash drop
• Revert changes: git stash pop

checkout remote branch

git fetch

git switch BRANCH_NAME

# or
git checkouto -B BRANCH_NAME origin/BRANCH_NAME 

revert or delete commits

• interactive wizard

# rework last commit ()
git reset HEAD^

# delete last commit
git reset --hard HEAD^

change old commit

Source

git rebase --interactive HEAD~10
# mark commit with 'e' or 'edit'
# change files and add to stage
git add <stuff>
git commit --amend --no-edit
git rebase --continue

clean files in history

If you want to delete passwords or other sensible stuff from git history use bfg. It does not touch your current commit (HEAD) just older commits.

# easy install (instead of working with bfg.jar)
brew install bfg

# example how to erase  password

# in git repo directory
echo "supersecret" > passwords.txt
bfg --replace-text passwords.txt
# push changed git history
git push --force

git submodules

# init submodule
git submodule update --init --recursive

# point submodule to HEAD
git submodule update --remote --merge

certs

• ignore:
• via system env variable: env GIT_SSL_NO_VERIFY=true
• or via cli: git config --global http.sslVerify "false"
• Windows:
• git config --global http.sslbackend channel

tag

# create tag and push (beware push only tags not commits)

git tag 1.2.3
#git tag -a 1.2.3 -m "message"
git push --tags

# delte remote tag
git push --delete oririn 1.2.3

# delete local
git tag -d 1.2.3

ssh generate keys

ssh-keygen -t rsa -b 4096

ssh remember passphrase

In bash:

echo 'eval `ssh-agent -s`' >> ~/.bashrc && source ~/.bashrc
ssh-add ~/.ssh/*_rsa

For WSL:

sudo apt install keychain
echo "eval `keychain --quiet --eval --agents ssh id_rsa`" >> ~/.bashrc  && source ~/.bashrc

work with gpg

Sign commitsa

# for one commit
git co -S -m ""
# for all
git config --global commit.gpgsign true

# in vscode add to settings json:
"git.enableCommitSigning": true

create and configure gpg keys:

• Gitlab doc

Save passphrase for twelve hours

echo "default-cache-ttl 43200" > ~/.gnupg/gpg-agent.conf