Frequently used git command

Details

There are some cases I need to use some specific git commands for some special purposes, like 

• Undoing git merge which haven't be pushed
• git reflog (Get the commit desired to return)
• git reset --hard sha
  
  
• Cherry-picking specific file changes from 1 commit to another
• git checkout <branch or sha of commit> -- filename
  
  
• Retrieve just 1 file from specific branch
• git checkout experiment -- app.js
  
  
• Show content changes which have been staged
• git diff --cached
  
  
• Show the diff of the same file between different commits of the same branch
• git diff HEAD^^ HEAD someFile (Show differences of someFile 2 commits before HEAD)
  
  
• Show file changes on specific commit (without diff information)
• git show --pretty="" --name-only {commit-sha}
  
  
• Show commits differences between 2 branches since branch created (file list)
• git log --oneline master..myBranch (Show changes since master branch)
• git log --oneline --no-merges master..myBranch (Show changes since master branch skipping merge commits)
  
  
• Get a list of branches created ordered with create date
• git branch --sort=-committerdate  # DESC
• git branch --sort=committerdate  # ASC
  
  
• Commit with standard input
• echo -e 'Update version number to v1.6.72.0\n\nfrom v1.6.70.0 to v1.6.72.0' | git commit /home/jacky/Documents/gitproj/p2_controller/docker/docker-compose-prod.yml /home/jacky/Documents/gitproj/p2_controller/docker/docker-compose-prod-upgrade.yml /home/jacky/Documents/gitproj/p2_controller/p2_controller/static_data/VERSION -F -

References

• Undo a Git merge that hasn't been pushed yet
• show commits since branch creation
• How to list all the files in a commit?
• How to cherry-pick changes from one file to another file?
• View git log without merge commits
• how-do-i-diff-the-same-file-between-two-different-commits-on-the-same-branch
• How to get just one file from another branch
• How can I get a list of Git branches, ordered by most recent commit?
  
• How do I show the changes which have been staged?

Multiple accounts management in gitlab

Background

Having 2 different gitlab accounts one is for company and the other one is personal, I would like both work independently on the machine at home, pull source code separately with their corresponding username and repository.

Problems

Very often I encountered a situation with permission denied in my company account while listing the remote repository of do anything remote (like git pull), but I can only make my personal account work without success on my company account. Turns out git client is wrongly picking the my personal account ssh information to login to my working account causing the "permission right" error.

Solutions

1. Refer to ~/.ssh/config and update the config file, add 1 more ssh entry to my company gitlab account as follows

Host anywhere.gitlab.com
  PubkeyAcceptedKeyTypes +ssh-rsa
  HostName gitlab.com
  IdentitiesOnly yes
  IdentityFile ~/.ssh/id_rsa2
  User ihmcjacky

Host maxwellhk.gitlab.com
  PubkeyAcceptedKeyTypes +ssh-rsa
  HostName gitlab.com
  IdentitiesOnly yes
  IdentityFile ~/.ssh/id_rsa
  User maxwellhk

Here, we have 2 users, 1 is ihmcjacky for my company usage, another is for my private usage, HostName parameter both specified as gitlab.com, but the Host which is very important, it acts as an alias for git client to identify which configuration it should refer to when trying to login to gitlab. Name anything familiar to you. In my case anywhere.gitlab.com and maxwellhk.gitlab.com.

2. Go to the desired project (in my case, company repository), navigate to .git folder and open config, configure the username and user email manually so as to let git client not to use globally configured settings for log in. Also in remote-origin url settings, configure as follows

url = git@anywhere.gitlab.com:p2Firmware/p2_controller.git

The anywhere.gitlab.com here is important, it is the alias we specified in ~/.ssh/config.

For safety, we can follow References > Multiple SSH keys for different accounts on Github or Gitlab, go through the processes, delete the cached keys and add back the ssh entries and check the ssh connection

3. Finally, add back the new origin URL to the project by using git remote set-url origin new.git.url/here

References

• Git pushing to remote GitHub repository as wrong user
  
• Multiple SSH keys for different accounts on Github or Gitlab
  
• Configure SSH to a different directory
  
• https://medium.com/uncaught-exception/setting-up-multiple-gitlab-accounts-82b70e88c437
  

Configuring Gitlab account in Linux & Windows

Background

I need to create a git working environment on my Windows 10 installed desktop, I then setup the git account, add the ssh key of the machine through the gitlab control panel but gitlab replied me with no access right when trying to git pull my project.

I tried

• Re-generate the RSA key and load again

But not working...

Solution

Turn out the username and the user account must match the one created in gitlab, git client will make use that account for the verification process with git server. I misunderstand that the user account can be arbitrary created on the fly.

Procedure

1. Configure the username and user account (MUST match with the one in gitlab / github, skip the --global parameter if you are managing multiple users)
• git config --global user.name "yourname"
• git config --global user.email“your@email.com"
2. Remove known_hosts (may not be necessary, it depends)
3. ssh-keygen -t rsa -C "whateverName"
4. Copy all text in /Users/your_user_directory/.ssh/id_rsa.pub
5. Go to setting in gitlab and add the public key for authentication
6. Set the git remote url with "git remote set-url origin https://gitUsername:gitPassword@gitlab.com/yourRepo.git"

Points to Note

Sometimes, login still failed with

sign_and_send_pubkey: signing failed: agent refused operation
Permission denied (publickey).
fatal: Could not read from remote repository.

Due to ssh-agent cannot find the keys attached, in such case we need to add the private key identities by running command

ssh-add

repeat step 6 and the remote origin may now be read


But in case... If it sill fails to log in for some error messages like no access rights to the repo, navigate to ~/.ssh/config, add the entry as follows.

Note: You can also specify multiple IdentityFile entries if you have same hostname using different key pairs, just add 1 more IdentityFile entry would be done, remember, you should put the private key in the IdentityFile option

Host gitlab.com
  PubkeyAcceptedKeyTypes +ssh-rsa
  HostName gitlab.com
  IdentityFile ~/.ssh/id_rsa_anywhere /*Private key directory here!!*/
  User git

And use all the possible keys for login

ssh git@gitlab.com -vv

After the configuration, gitlab should be able to login and fetch updates again

References

• https://gitlab.com/gitlab-com/support-forum/-/issues/638#note_32211207
• https://blog.csdn.net/jingtingfengguo/article/details/51892864
• https://stackoverflow.com/questions/4220416/can-i-specify-multiple-users-for-myself-in-gitconfig
• https://askubuntu.com/questions/762541/ubuntu-16-04-ssh-sign-and-send-pubkey-signing-failed-agent-refused-operation
• https://dotblogs.com.tw/Echo/2017/06/28/Linux_AuthorizedKeys_Setting
  

Setup VCS Using Redmine + Git

We all know that Git is a very good VCS, with redmine, like Bugzilla, we have even better control and graphical view on our repository, and this is undoubtedly aid development. The following is how to make the whole VCS system happens.

What we need
1) Git (of course!)
2) Redmine
3) Apache Server

Procedure
1) Install all the necessary components respectively
sudo apt-get install apache2
sudo apt-get install mysql-server
sudo apt-get install redmine-mysql
sudo apt-get install libapache2-mod-passenger
sudo apt-get install redmine
sudo apt-get install git-core

2) Set up soft link from redmine source to the Apache source
sudo ln -s /usr/share/redmine/public /var/www/redmine

3) mod passenger needs www-data to execute, add the following to /etc/apache2/mods-available/passenger.conf

vi /etc/apache2/mods-available/passenger.conf

PassengerDefaultUser www-data

 4) Add redmine's web directory to Apache2's sites-available/default

                RailsBaseURI /redmine
                PassengerAppRoot /usr/share/redmine
                RailsEnv production
                PassengerResolveSymlinksInDocumentRoot on

5) Setup plugin linkage
 ln -s /var/cache/redmine/default/plugin_assets /usr/share/redmine/public/

6) Create new repository (server side), note that the directory should be with owner "www-data"

cd /var/www

mkdir test-repo.git

cd test-repo.git

git --bare init

git update-server-info

chown -R www-data.www-data .

 7) Enable webDAV
a2enmod dav_fs
a2enmod dav

If high security is required, carry on, if not, restart apache and all services will be done

8) Create the following file
/etc/apache2/conf.d/git.conf

9) Configure the repository path for authentication

        DAV on

        AuthType Basic

        AuthName "Git"

        AuthUserFile /etc/apache2/passwd.git

        Require valid-user

10) Create user which can access the repository
 htpasswd -c /etc/apache2/passwd.git

11) Restart Apache service
/etc/init.d/apache2 restart

Done! You have made a git VCS with redmine geared!

Almost forgot, modifying the config file in .git directory is necessary for authentication when pushing

[remote "origin"]

fetch = +refs/heads/*:refs/remotes/origin/*

url = http://username:password@git.repository.url/repo.git

References:
- Linking git remote server to Apache
http://blog.bobbyallen.me/2012/07/23/installing-a-git-server-using-apache-webdav-on-ubuntu-server-12-04/

- Installing Apache + Git + Redmine
http://blog.chiichen.com/2014/05/raspberry-pi-redmine.html

- Git config fix on http/https authentication
http://stackoverflow.com/questions/5264949/cannot-push-git-to-remote-repository-with-http-https

- Others
https://randomthoughtsgr.wordpress.com/2011/10/17/redmine-sub-uri-and-apache-configuration/