tutorial - how to use git




Git for beginners: The definitive practical guide (20)

Ok, after seeing this post by PJ Hyett, I have decided to skip to the end and go with Git.

So what I need is a beginner's practical guide to Git. "Beginner" being defined as someone who knows how to handle their compiler, understands to some level what a Makefile is, and has touched source control without understanding it very well.

"Practical" being defined as this person doesn't want to get into great detail regarding what Git is doing in the background, and doesn't even care (or know) that it's distributed. Your answers might hint at the possibilities, but try to aim for the beginner that wants to keep a 'main' repository on a 'server' which is backed up and secure, and treat their local repository as merely a 'client' resource.

So:

Installation/Setup

Working with the code

Tagging, branching, releases, baselines

Other

Other Git beginner's references

Delving into Git

I will go through the entries from time to time and 'tidy' them up so they have a consistent look/feel and it's easy to scan the list - feel free to follow a simple "header - brief explanation - list of instructions - gotchas and extra info" template. I'll also link to the entries from the bullet list above so it's easy to find them later.


Checking Out Code

First go to an empty dir, use "git init" to make it a repository, then clone the remote repo into your own.

git clone [email protected]:/dir/to/repo

Wherever you initially clone from is where "git pull" will pull from by default.


Console UI - Tig

Installation:

apt-get install tig

Usage

While inside a git repo, type 'tig', to view an interactive log, hit 'enter' on any log to see more information about it. h for help, which lists the basic functionality.

Trivia

"Tig" is "Git" backwards.


Git Reset

Say you make a pull, merge it into your code, and decide you don't like it. Use git-log, or tig, and find the hash of wherever you want to go back to (probably your last commit before the pull/merge) copy the hash, and do:

# Revert to a previous commit by hash:
git-reset --hard <hash>

Instead of the hash, you can use HEAD^ as a shortcut for the previous commit.

# Revert to previous commit:
git-reset --hard HEAD^

How can I create a branch on a remote repository?

Assuming that you have cloned your remote repository from some single remote repository.

# create a new branch locally
git branch name_of_branch
git checkout name_of_branch
# edit/add/remove files    
# ... 
# Commit your changes locally
git add fileName
git commit -m Message
# push changes and new branch to remote repository:
git push origin name_of_branch:name_of_branch

How do you branch?

The default branch in a git repository is called master.

To create a new branch use

git branch <branch-name>

To see a list of all branches in the current repository type

git branch

If you want to switch to another branch you can use

git checkout <branch-name>

To create a new branch and switch to it in one step

git checkout -b <branch-name>

To delete a branch, use

git branch -d <branch-name>

To create a branch with the changes from the current branch, do

git stash
git stash branch <branch-name>

How do you compare two revisions of a file, or your current file and a previous revision?

Compare command is git diff.

To compare 2 revisions of a file:

$ git diff <commit1> <commit2> <file_name>

That diffs commit1 against commit2; if you change order then files are diffed the other way round, which may not be what you expect...

To compare current staged file against the repository:

$ git diff --staged <file_name>

To compare current unstaged file against the repository:

$ git diff <file_name>

How do you merge branches?

If you want to merge a branch (e.g. master to release), make sure your current branch is the target branch you'd like to merge into (use git branch or git status to see your current branch).

Then use

git merge master

(where master is the name of the branch you want to merge with the current branch).

If there are any conflicts, you can use

git diff

to see pending conflicts you have to resolve.


How do you see the history of revisions to a file?

git log -- filename

How to install Git

On Windows:

Install msysgit

There are several downloads:

  • Git: Use this unless you specifically need one of the other options below.
  • PortableGit: Use this if you want to run Git on a PC without installing on that PC (e.g. running Git from a USB drive)
  • msysGit: Use this if you want to develop Git itself. If you just want to use Git for your source code, but don't want to edit Git's source code, you don't need this.

This also installs a Cygwin bash shell, so you can use the git in a nicer shell (than cmd.exe), and also includes git-gui (accessible via git gui command, or the Start > All Programs > Git menu)

Mac OS X

Use the git-osx-installer, or you can also install from source

Via a package manager

Install git using your native package manager. For example, on Debian (or Ubuntu):

apt-get install git-core

Or on Mac OS X, via MacPorts:

sudo port install git-core+bash_completion+doc

…or fink:

fink install git

…or Homebrew:

brew install git

On Red Hat based distributions, such as Fedora:

yum install git

In Cygwin the Git package can be found under the "devel" section

From source (Mac OS X/Linux/BSD/etc.)

In Mac OS X, if you have the Developer Tools installed, you can compile Git from source very easily. Download the latest version of Git as a .tar.bz or .tar.gz from http://git-scm.com/, and extract it (double click in Finder)

On Linux/BSD/etc. it should be much the same. For example, in Debian (and Ubuntu), you need to install the build-essential package via apt.

Then in a Terminal, cd to where you extracted the files (Running cd ~/Downloads/git*/ should work), and then run..

./configure && make && sudo make install

This will install Git into the default place (/usr/local - so git will be in /usr/local/bin/git)

It will prompt you to enter your password (for sudo), this is so it can write to the /usr/local/ directory, which can only be accessed by the "root" user so sudo is required!

If you with to install it somewhere separate (so Git's files aren't mixed in with other tools), use --prefix with the configure command:

./configure --prefix=/usr/local/gitpath
make
sudo make install

This will install the git binary into /usr/local/bin/gitpath/bin/git - so you don't have to type that every time you, you should add into your $PATH by adding the following line into your ~/.profile:

export PATH="${PATH}:/usr/local/bin/gitpath/bin/"

If you do not have sudo access, you can use --prefix=/Users/myusername/bin and install into your home directory. Remember to add ~/bin/ to $PATH

The script x-git-update-to-latest-version automates a lot of this:

This script updates my local clone of the git repo (localy at ~/work/track/git), and then configures, installs (at /usr/local/git-git describe) and updates the /usr/local/git symlink.

This way, I can have /usr/local/git/bin in my PATH and I'm always using the latest version.

The latest version of this script also installs the man pages. You need to tweak your MANPATH to include the /usr/local/git/share/man directory.


How to track remote branches

Assuming there is a remote repository that you cloned your local repository from and also assuming that there is a branch named 'some_branch' on that remote repository, here is how to track it locally:

# list remote branches
git branch -r

# start tracking one remote branch
git branch --track some_branch origin/some_branch

# change to the branch locally
git checkout some_branch

# make changes and commit them locally
....

# push your changes to the remote repository:
git push

Getting the latest Code

$ git pull <remote> <branch> # fetches the code and merges it into 
                             # your working directory
$ git fetch <remote> <branch> # fetches the code but does not merge
                              # it into your working directory

$ git pull --tag <remote> <branch> # same as above but fetch tags as well
$ git fetch --tag <remote> <branch> # you get the idea

That pretty much covers every case for getting the latest copy of the code from the remote repository.


How do I delete a branch on a remote repository?

Perform a push in your remote using : before the name of the branch

git push origin :mybranchname

being origin the name of your remote and mybranchname the name of the branch about to be deleted

http://help.github.com/remotes/


Git Magic is all you'll ever need. Guaranteed or your money back!


git status is your friend, use it often. Good for answering questions like:

  • What did that command just do?
  • What branch am I on?
  • What changes am I about to commit, and have I forgotten anything?
  • Was I in the middle of something last time I worked on this project (days, weeks, or perhaps months ago)?

Unlike, say svn status, git status runs nigh-instantly even on large projects. I often found it reassuring while learning git to use it frequently, to make sure my mental model of what was going on was accurate. Now I mostly just use it to remind myself what I've changed since my last commit.

Obviously, it's much more useful if your .gitignore is sanely configured.


A real good paper for understanding how Git works is The Git Parable. Very recommended!



I got started with the official Git tutorial. I think it's practical enough for beginners (I was, and still am, a beginner, by your definition! I barely grasp makefiles, I've only played a bit with Apache Subversion, etc.).



Well, despite the fact that you asked that we not "simply" link to other resources, it's pretty foolish when there already exists a community grown (and growing) resource that's really quite good: the Git Community Book. Seriously, this 20+ questions in a question is going to be anything but concise and consistent. The Git Community Book is available as both HTML and PDF and answers many of your questions with clear, well formatted and peer reviewed answers and in a format that allows you to jump straight to your problem at hand.

Alas, if my post really upsets you then I'll delete it. Just say so.


Why yet another howto? There are really good ones on the net, like the git guide which is perfect to begin. It has good links including the git book to which one can contribute (hosted on git hub) and which is perfect for this collective task.

On , I would really prefer to see your favorite tricks !

Mine, which I discovered only lately, is git stash, explained here, which enables you to save your current job and go to another branch

EDIT: as the previous post, if you really prefer stackoverlow format with posts as a wiki I will delete this answer





version-control