Git 101 – Quick Start Guide

Here is a set of commands I found using… There might be a lot of other useful commands.

Setting up a Git project

If you want to work with an existing project, clone it:

$ git clone <url> - for example: git clone https://greenido@github.com/greenido/html5-boilerplate.git

If you do not have an existing git project, create one:

$ cd project/
$ git init          # initializes the repository
$ git add .         # add those 'unknown' files
$ git commit        # commit all changes, edit changelog entry
$ git rm --cached <file>... # ridiculously complicated command to undo, in case you forgot .gitignore

Git will look for a file named .gitignore in the root of your repository which contains a set of shell patterns to ignore in file paths.

Branching and merging

$ git checkout -b linux-work        # create a new branch named "linux-work"
$ <make changes>
$ git commit -a
$ git checkout master               # go back to master branch
$ git merge linux-work              # merge changesets from linux-work (Git >= 1.5)
$ git pull . linux-work             # merge changesets from linux-work (all Git versions)

Importing patches

$ git apply < ../p/foo.patch
$ git commit -a

Exporting a patch

$ <make changes>
$ git commit -a -m "commit message"
$ git format-patch HEAD^  # creates 0001-commit-message.txt
                          # (HEAD^ means every patch since one revision before the
                          # tip of the branch, also known as HEAD)

Network support

# clone from the primary Git repo
$ git clone git@github.com:greenido/html5-boilerplate.git
$ cd git

# pushing changes to a remote repo with SSH
$ git push user@github.com:my-repository.git/

# fetch changes to a remote branch into a local branch
$ git fetch user@example.com:my-repository.git/ remote-branch:local-branch

# merge changes from a remote machine
bar$ git pull git://foo/repo.git/ branch

# Serve repository via git protocol
$ cd /my/repository/
$ touch .git/git-daemon-export-ok
$ git daemon  # now others can fetch from git://your.machine/my/repository/.git/

# Set up a bare (= without working directory) repository (e.g. on a webserver)
$ mkdir my-repo.git
$ cd my-repo.git
$ git --bare init
$ chmod a+x hooks/post-update # this is needed for HTTP transport
                                      # you need to populate this repository via push

Inspecting revisions

# inspect history visually
$ gitk       # this opens a Tk window, and shows you how the revisions are connected

# inspect history
$ git log    # this pipes a log of the current branch into your PAGER
$ git log -p # ditto, but append a patch after each commit message

# inspect a specific commit
$ git show HEAD    # show commit info, diffstat and patch
                      # of the tip of the current branch

Referring to revisions

# by name
$ git log v1.0.0   # show history leading up to tag "v1.0.0"
$ git log master   # show history of branch "master"

# relative to a name
$ git show master^   # show parent to last revision of master
$ git show master~2  # show grand parent to tip of master
$ git show master~3  # show great grand parent to tip of master (you get the idea)

# by output of "git describe"
$ git show v1.4.4-g730996f  # you get this string by calling "git describe"

# by hash (internally, all objects are identified by a hash)
$ git show f665776185ad074b236c00751d666da7d1977dbe
$ git show f665776   # a unique prefix is sufficient

# tag a revision
$ git tag v1.0.0                      # make current HEAD known as "v1.0.0"
$ git tag interesting v1.4.4-g730996f # tag a specific revision (not HEAD)

Comparing revisions

# diff between two branches
$ git diff origin..master            # pipes a diff into PAGER
$ git diff origin..master > my.patch # pipes a diff into my.patch

# get diffstat of uncommitted work
$ git diff --stat HEAD

Last But Not…

I recommend this quick good GIT course. Feel free to check around: https://github.com/greenido

Other Resources

* Simple and contain most of the basic commands you need: http://rogerdudler.github.io/git-guide/
* A ‘Game’ that will teach you Git: http://pcottle.github.io/learnGitBranching/


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