How do you create a new project/repository?

A git repository is simply a directory containing a special .git directory.

This is different from "centralised" version-control systems (like subversion), where a "repository" is hosted on a remote server, which you checkout into a "working copy" directory. With git, your working copy is the repository.

Simply run git init in the directory which contains the files you wish to track.

For example,

cd ~/code/project001/
git init

This creates a .git (hidden) folder in the current directory.

To make a new project, run git init with an additional argument (the name of the directory to be created):

git init project002

(This is equivalent to: mkdir project002 && cd project002 && git init)

To check if the current current path is within a git repository, simply run git status - if it's not a repository, it will report "fatal: Not a git repository"

You could also list the .git directory, and check it contains files/directories similar to the following:

$ ls .git
HEAD         config       hooks/       objects/
branches/    description  info/        refs/

If for whatever reason you wish to "de-git" a repository (you wish to stop using git to track that project). Simply remove the .git directory at the base level of the repository.

cd ~/code/project001/
rm -rf .git/

Caution: This will destroy all revision history, all your tags, everything git has done. It will not touch the "current" files (the files you can currently see), but previous changes, deleted files and so on will be unrecoverable!

GUIs for git

Git GUI

Included with git — Run git gui from the command line, and the Windows msysgit installer adds it to the Start menu.

Git GUI can do a majority of what you'd need to do with git. Including stage changes, configure git and repositories, push changes, create/checkout/delete branches, merge, and many other things.

One of my favourite features is the "stage line" and "stage hunk" shortcuts in the right-click menu, which lets you commit specific parts of a file. You can achieve the same via git add -i, but I find it easier to use.

It isn't the prettiest application, but it works on almost all platforms (being based upon Tcl/Tk)

Screenshots | a screencast

GitK

Also included with git. It is a git history viewer, and lets you visualise a repository's history (including branches, when they are created, and merged). You can view and search commits.

Goes together nicely with git-gui.

Gitnub

Mac OS X application. Mainly an equivalent of git log, but has some integration with github (like the "Network view").

Looks pretty, and fits with Mac OS X. You can search repositories. The biggest critisism of Gitnub is that it shows history in a linear fashion (a single branch at a time) - it doesn't visualise branching and merging, which can be important with git, although this is a planned improvement.

Download links, change log and screenshots | git repository

GitX

Intends to be a "gitk clone for OS X".

It can visualise non-linear branching history, perform commits, view and search commits, and it has some other nice features like being able to "Quicklook" any file in any revision (press space in the file-list view), export any file (via drag and drop).

It is far better integrated into OS X than git-gui/gitk, and is fast and stable even with exceptionally large repositories.

The original git repository pieter has not updated recently (over a year at time of writing). A more actively maintained branch is available at brotherbard/gitx - it adds "sidebar, fetch, pull, push, add remote, merge, cherry-pick, rebase, clone, clone to"

Download | Screenshots | git repository | brotherbard fork | laullon fork

SmartGit

From the homepage:

SmartGit is a front-end for the distributed version control system Git and runs on Windows, Mac OS X and Linux. SmartGit is intended for developers who prefer a graphical user interface over a command line client, to be even more productive with Git — the most powerful DVCS today.

You can download it from their website.

Download

TortoiseGit

TortoiseSVN Git version for Windows users.

It is porting TortoiseSVN to TortoiseGit The latest release 1.2.1.0 This release can complete regular task, such commit, show log, diff two version, create branch and tag, Create patch and so on. See ReleaseNotes for detail. Welcome to contribute this project.

Download

QGit

QGit is a git GUI viewer built on Qt/C++.

With qgit you will be able to browse revisions history, view patch content and changed files, graphically following different development branches.

Download

gitg

gitg is a git repository viewer targeting gtk+/GNOME. One of its main objectives is to provide a more unified user experience for git frontends across multiple desktops. It does this not be writing a cross-platform application, but by close collaboration with similar clients for other operating systems (like GitX for OS X).

Features

• Browse revision history.
• Handle large repositories (loads linux repository, 17000+ revisions, under 1 second).
• Commit changes.
• Stage/unstage individual hunks.
• Revert changes.
• Show colorized diff of changes in revisions.
• Browse tree for a given revision.
• Export parts of the tree of a given revision.
• Supply any refspec which a command such as 'git log' can understand to built the history.
• Show and switch between branches in the history view.

Download: releases or source

Gitbox

Gitbox is a Mac OS X graphical interface for Git version control system. In a single window you see branches, history and working directory status.

Everyday operations are easy: stage and unstage changes with a checkbox. Commit, pull, merge and push with a single click. Double-click a change to show a diff with FileMerge.app.

Download

Gity

The Gity website doesn't have much information, but from the screenshots on there it appears to be a feature rich open source OS X git gui.

Download or source

Meld

Meld is a visual diff and merge tool. You can compare two or three files and edit them in place (diffs update dynamically). You can compare two or three folders and launch file comparisons. You can browse and view a working copy from popular version control systems such such as CVS, Subversion, Bazaar-ng and Mercurial [and Git].

Downloads

Katana

A Git GUIfor OSX by Steve Dekorte.

At a glance, see which remote branches have changes to pull and local repos have changes to push. The git ops of add, commit, push, pull, tag and reset are supported as well as visual diffs and visual browsing of project hieracy that highlights local changes and additions.

Free for 1 repository, $25 for more.

Download

Sprout (formerly GitMac)

Focuses on making Git easy to use. Features a native Cocoa (mac-like) UI, fast repository browsing, cloning, push/pull, branching/merging, visual diff, remote branches, easy access to the Terminal, and more.

By making the most commonly used Git actions intuitive and easy to perform, Sprout (formerly GitMac) makes Git user-friendly. Compatible with most Git workflows, Sprout is great for designers and developers, team collaboration and advanced and novice users alike.

Download | Website

Tower

A feature-rich Git GUI for Mac OSX. 30-day free trial, $59USD for a single-user license.

Download | Website

EGit

EGit is an Eclipse Team provider for the Git version control system. Git is a distributed SCM, which means every developer has a full copy of all history of every revision of the code, making queries against the history very fast and versatile.

The EGit project is implementing Eclipse tooling on top of the JGit Java implementation of Git.

Download | Website

Git Extensions

Open Source for Windows - installs everything you need to work with Git in a single package, easy to use.

Git Extensions is a toolkit to make working with Git on Windows more intuitive. The shell extension will intergrate in Windows Explorer and presents a context menu on files and directories. There is also a Visual Studio plugin to use git from Visual Studio.

Download

Big thanks to dbr for elaborating on the git gui stuff.

SourceTree

SourceTree is a free Mac client for Git, Mercurial and SVN. Built by Atlassian, the folks behind BitBucket, it seems to work equally well with any VC system, which allows you to master a single tool for use with all of your projects, however they're version-controlled. Feature-packed, and FREE.

Expert-Ready & Feature-packed for both novice and advanced users:

Review outgoing and incoming changesets. Cherry-pick between branches. Patch handling, rebase, stash / shelve and much more.

Download | Website

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.

How to configure it to ignore files:

The ability to have git ignore files you don't wish it to track is very useful.

To ignore a file or set of files you supply a pattern. The pattern syntax for git is fairly simple, but powerful. It is applicable to all three of the different files I will mention bellow.

• A blank line ignores no files, it is generally used as a separator.
• Lines staring with # serve as comments.
• The ! prefix is optional and will negate the pattern. Any negated pattern that matches will override lower precedence patterns.
• Supports advanced expressions and wild cards
  • Ex: The pattern: *.[oa] will ignore all files in the repository ending in .o or .a (object and archive files)
• If a pattern has a directory ending with a slash git will only match this directory and paths underneath it. This excludes regular files and symbolic links from the match.
• A leading slash will match all files in that path name.
  • Ex: The pattern /*.c will match the file foo.c but not bar/awesome.c

Great Example from the gitignore(5) man page:

$ git status
[...]
# Untracked files:
[...]
#       Documentation/foo.html
#       Documentation/gitignore.html
#       file.o
#       lib.a
#       src/internal.o
[...]
$ cat .git/info/exclude
  # ignore objects and archives, anywhere in the tree.
  *.[oa]
$ cat Documentation/.gitignore
# ignore generated html files,
*.html
# except foo.html which is maintained by hand
!foo.html
$ git status
[...]
# Untracked files:
[...]
#       Documentation/foo.html
[...]

Generally there are three different ways to ignore untracked files.

1) Ignore for all users of the repository:

Add a file named .gitignore to the root of your working copy.

Edit .gitignore to match your preferences for which files should/shouldn't be ignored.

git add .gitignore 

and commit when you're done.

2) Ignore for only your copy of the repository:

Add/Edit the file $GIT_DIR/info/exclude in your working copy, with your preferred patterns.

Ex: My working copy is ~/src/project1 so I would edit ~/src/project1/.git/info/exclude

You're done!

3) Ignore in all situations, on your system:

Global ignore patterns for your system can go in a file named what ever you wish.

Mine personally is called ~/.gitglobalignore

I can then let git know of this file by editing my ~/.gitconfig file with the following line:

core.excludesfile = ~/.gitglobalignore

You're done!

I find the gitignore man page to be the best resource for more information.

How do you 'tag' a particular set of revisions

How do you 'mark' 'tag' or 'release' a particular set of revisions for a particular set of files so you can always pull that one later?

Using the git tag command.

To simply "tag" the current revision, you would just run..

git tag -a thetagname
git tag -a 0.1
git tag -a 2.6.1-rc1 -m 'Released on 01/02/03'

To list the current tags, simply run git tag with no arguments, or -l (lower case L):

$ git tag -a thetagname # and enter a message, or use -m 'My tag annotation'
$ git tag -l
thetagname

To delete a tag, you use the -d flag:

$ git tag -d thetagname 
Deleted tag 'thetagname'
$ git tag
[no output]

To tag a specific (previous) commit, you simply do..

git tag [tag name] [revision SHA1 hash]

For example:

git tag 1.1.1 81b15a68c6c3e71f72e766931df4e6499990385b

Note: by default, git creates a "lightweight" tag (basically a reference to a specific revision). The "right" way is to use the -a flag. This will launch your editor asking for a tag message (identical to asking for a commit message, you can also use the -m flag to supply the tag message on the command line). Using an annotated tag creates an object with its own ID, date, tagger (author), and optionally a GPG signature (using the -s tag). For further information on this, see this post

git tag mytagwithmsg -a -m 'This is a tag, with message'

And to list the tags with annotations, use the -n1 flag to show 1 line of each tag message (-n245 to show the first 245 lines of each annotation, and so on):

$ git tag -l -n1
mytagwithmsg    This is a tag, with message

For more information, see the git-tag(1) Manual Page

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.

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^

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.

Commit Changes

Once you've edited a file, you need to commit your changes to git. When you execute this command it will ask for a commit message - which is just a simple bit of text that tells everyone what you've changed.

$ git commit source/main.c

Will commit the file main.c in the directory ./source/

$ git commit -a # the -a flag pulls in all modified files

will commit all changed files (but not new files, those need to be added to the index with git-add). If you want to commit only certain files then you will need to stage them first with git-add and then commit without the -a flag.

Commiting only changes your local repository though not the remote repositories. If you want to send the commits to the remote repository then you will need to do a push.

$ git push <remote> <branch> # push new commits to the <branch> on the <remote> repository

For someone coming from CVS or SVN this is a change since the commit to the central repository now requires two steps.

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>

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

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

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 stackoverflow, 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

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.

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.).

Push and pull changes

In an simplified way, just do git push and git pull. Changes are merged and if there's a conflict git will let you know and you can resolve it manually.

When you first push to a remote repository you need to do a git push origin master (master being the master branch). From then on you just do the git push.

Push tags with git push --tags.

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 user@host.com:/dir/to/repo

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

Resource: Definitely check out Scott Chacon's Gitcasts, especially the Railsconf talk.

Github is awesome and also has some helpful guides.

WRT good GUIs/frontends, you may also want to check out qgit which is a cross-platform (Linux/Win32) repository viewer for Git and can be also used as high level frontend for the most common Git operations, in fact it can be easily enhanced by so called "custom actions" so that users can provide customized actions.

I found this post to be very useful to get me started. I still need to read the book and other resources but the post was helpful in, as the title says, "understanding git conceptually". I also recommend taking the Git & GitHub course offered at RubyLearning.

One more item I really think should be in this list, probably very useful for beginners:

Don't Panic

What if I've done some commits and then I did something scary, like maybe a rebase, and now something—or even everything—seems to be lost? (Rebase seems to be the one that gets most people the first time, so I'm concentrating on it. While git rebase --abort helps a lot, sometimes you'll find that you botched an edit during an interactive rebase, for instance, and let the rebase finish and now you want to get your old stuff back. And then there are things like filter-branch...)

One key git principle is that it never actually deletes anything you've committed. ("What, never?" "No, never!" "What, never?" "Well, hardly ever!") If you have not run git gc, it's still in there. It may take some digging around to find your previous work, but if you did some successful git commits earlier, then, for instance, even your apparently-wrecked series of commits from a tragic rebase error are still in there, normally for at least a month (technically, until the "reflogs" expire).

It's important to keep in mind that each branch name labels—or points to—a "commit-ID". These are the the funny numbers like 7cc5272. Many of the things you do, like adding a new commit to a branch, make the branch name point to a new, different commit-ID. Each commit-ID has a link pointing back to some previous commit-ID(s), and this is what actually makes up a "branch" full of commits.

The rebase entry talks about "rewriting history," and commands like git filter-branch also "rewrite history," but they do it not by destroying the previous history, but rather by adding new history. Once the new history is in place, git will "move the labels around" so that it looks like history has changed. If you are on your fix-nasty-bug branch and do a git rebase and manage to wreck things, the label fix-nasty-bug now refers to the wreckage, but the original versions are still there. Rebase in particular makes a temporary (non-moving, not-a-branch) label spelled ORIG_HEAD that lets you find them. The filter-branch command saves all the original names as well. In some cases, there may be no obvious name, but the commits can always be found. If necessary, find yourself a "git guru" and explain what you did that led to the wreckage.

(The command git reflog show can also help with finding commit-IDs.)

If you have found what you think is some or all of your previous work, try:

git log <commit-ID>   # ORIG_HEAD after a bad rebase, for instance
git show <commit-ID>  # or some long SHA1 value you can still see in a window

If it looks right or useful, put a name to it:

git branch recover-my-stuff ORIG_HEAD

and it's all back again! In fact, now both your bad rebase and your original work are in your git repo "forever" (or at least, until you delete the branch names and let a few months go by, and then they get garbage-collected). You can put as many names to as many recovered commits as you like. (Branch names are virtually free, except for cluttering up your git branch output, and of course they also keep commits from being garbage-collected. You can also, or instead, put tags on specific commit-IDs, if you prefer those.)