Charles Poli, PhD

Head of Artificial Intelligence,
Cambridge Quantum Computing Limited, London.

: a super short documentation


Git is a distributed revision control system, it allows to: To do so, Git stores the different versions of your project in a repository located in your project directory.

Installation


Visit the website http://git-scm.com to download Git and find the complete documentation.
During the installation, select Git from Git bash only. When this is done,
for Mac/Linux:
  launch a Terminal.
for Windows:
  menu → Git → Git Bash


Create a Git account

  • git config --global user.name "Alex Dumas"
  • git config --global user.email ”alex@dumas.fr”

Git commands


initialize Git


Go to the project directory using Terminal/Powershell:
  • cd project
  • git init
The last command will create a hidden Git repository.

First backup (commit)


The first commit is done in 2 steps:
  • git add .
  • git commit -m ”first comments”
The first command sends the files from the Working area to the Staging area.
The second command sends the files from the Staging area to the Repository.

Next commits

  • git commit -am ”new comments”

Useful commands


Check the difference between the working copy and the repository.
  • git status
Get commit history
  • git log
Delete a Git project
  • rm -rf .git

An Example


creation of a folder containing a very simple file:
  • mkdir git-test
  • cd git-test
  • emacs file.txt
File.txt:
one line
Git initialization
  • git init
       Initialized empty Git repository in /Users/adumas/git-test/.git/
Git first commit
  • git add .
  • git commit -m "first commit: 1 text file"
    •   [master (root-commit) 209f961] first commit: 1 text file
      1 file changed, 1 insertion(+)
      create mode 100644 file.txt
check the repository
  • git log
    •   commit 209f961f9c8cfaad8f5689d354faa240ee161f7b
      Author: Alex Dumas "alex@dumas.fr"
      Date: Sat May 16 17:27:06 2015 +0100
      first commit: 1 text file
modification the text file
first line
second line
third line
check the difference between the working area and the repository:
  • git diff file.txt
    •   diff --git a/file.txt b/file.txt
      index e3c0674..ae0d792 100644
      --- a/file.txt
      +++ b/file.txt
      @@ -1 +1,3 @@
      -one line
      +first line
      +second line
      +third line
Commit the new file
  • git commit -am "second commit: 3 lines"
    •    [master e869c09] second commit: 3 lines
       1 file changed, 3 insertions(+), 1 deletion(-)
Check the commits history
  • git log
    •   commit e869c09ec49f611828ac45d48a5ea1106a806ac4
      Author: Alex Dumas "alex@dumas.fr"
      Date: Sat May 16 17:28:57 2015 +0100
      second commit: 3 lines
      commit 209f961f9c8cfaad8f5689d354faa240ee161f7b
      Author: Alex Dumas "alex@dumas.fr"
      Date: Sat May 16 17:27:06 2015 +0100
      first commit: 1 text file
Note that a tracking number is associated to each commit:

the first commit has the tracking number:
209f961f9c8cfaad8f5689d354faa240ee161f7b

the second commit has the tracking number:
e869c09ec49f611828ac45d48a5ea1106a806ac4

Now, let's go back to the first commit:
  • git checkout 209f961f9c8cf -- file.txt
  • # note that the full tracking number is not needed
Commit the new version
  • git commit -am "third commit: going back to first commit"
Last check of the commits history
  • git log
    •   commit 7cd3dc1a4c2bf9a974231c666f0c5b9b0ae49987
      Author: Alex Dumas "alex@dumas.fr"
      Date: Sat May 16 17:30:34 2015 +0100
      third commit: going back to first commit
      commit e869c09ec49f611828ac45d48a5ea1106a806ac4
      Author: Alex Dumas alex@dumas.fr
      Date: Sat May 16 17:28:57 2015 +0100
      second commit: 3 lines
      commit 209f961f9c8cfaad8f5689d354faa240ee161f7b
      Author: Alex Dumas alex@dumas.fr
      Date: Sat May 16 17:27:06 2015 +0100
      first commit: 1 text file