Creating a local repository

From scratch:

$ mkdir git-test
$ cd git-test
$ git init
Initialized empty Git repository in /home/pallier/cours/Python/version_control/git-test/.git/

Importing from an existing project on the Internet:

$ git clone git clone https://github.com/chrplr/pyepl_examples

Adding files to the local repository

The command 'git add' is used to tell git which files it must track:

$ echo 'essai1' > readme.txt
$ git add readme.txt

Interestingly, you can also add whole directories, for example:

$ git add .

Note that it is possible to prevent certain files to be tracked (see https://help.github.com/articles/ignoring-files).

To check which files are currently being tracked (or staged), use the command git status:

$ git status
# On branch master
#
# Initial commit
#
# Changes to be committed:
#   (use "git rm --cached <file>..." to unstage)
#
#       new file:   readme.txt
#

Creating a snapshot, or commiting

Once you are satisfied with the files in your working directory, you can take a snapshot. This is also called commiting your changes:

$ git commit
[master (root-commit) a7a3a47] First commit
1 file changed, 1 insertion(+)
create mode 100644 readme.txt

Modifying the project

Let us now modify the file readme.txt in the working directory:

$ echo 'line2' >readme.txt

The command git status allows us to compare the state of files in the current directory and in the repository:

$ git status
# On branch master
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#       modified:   readme.txt
#
no changes added to commit (use "git add" and/or "git commit -a")
$ git add readme.txt
$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#       modified:   readme.txt
#

Let us create a new file, readme2.txt:

$ echo 'trial2' >readme2.txt
$ ls
readme2.txt  readme.txt
$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#       modified:   readme.txt
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#       readme2.txt

We now add readme2.txt to the repository:

$ git add readme2.txt
$ git commit
[master a7e25a1] First revision; added readme2.txt
2 files changed, 2 insertions(+), 1 deletion(-)
create mode 100644 readme2.txt

Let us consult the history of the project:

$ git log
commit a7e25a158ce52a75c62381420f7dc375de631b1b
Author: Christophe Pallier <christophe@pallier.org>
Date:   Mon Aug 27 10:49:54 2012 +0200

    First revision; added readme2.txt

commit a7a3a47edfae9d7c720356b691000a81ded73906
Author: Christophe Pallier <christophe@pallier.org>
Date:   Mon Aug 27 10:47:32 2012 +0200

    First commit



$ git status
# On branch master
nothing to commit (working directory clean)

Renaming a file

To rename a tracked file, you should use git mv rather then just mv:

$ git mv file.ori file.new

Recovering a file deleted by accident

Let us delete readme2.txt "by accident":

$ rm readme2.txt # oops
$ ls
readme.txt
$ git status
# On branch master
# Changes not staged for commit:
#   (use "git add/rm <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#       deleted:    readme2.txt
#
no changes added to commit (use "git add" and/or "git commit -a")

To recover it:

$ git checkout -- readme2.txt
$ ls
readme2.txt  readme.txt
$ cat readme2.txt
trial2

Checking for changes

Let us now modify readme2.txt and then compare the file in the current directory from the ones in the last commit:

$ echo 'line2 of 2' > readme2.txt
$ git diff
diff --git a/readme2.txt b/readme2.txt
index 33d1e15..e361691 100644
--- a/readme2.txt
+++ b/readme2.txt
@@ -1 +1 @@
-trial2
+line2 of 2
$ git status
# On branch master
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#       modified:   readme2.txt
#
no changes added to commit (use "git add" and/or "git commit -a")

Faster commit

The command 'git commit -a' performs both a 'git add' and a 'git commit':

$ git commit -a
[master a74359e] Second revision
1 file changed, 1 insertion(+), 1 deletion(-)
$ git log
commit a74359e148aff0c369b6ddd482d0fbe0e7ad93ab
Author: Christophe Pallier <christophe@pallier.org>
Date:   Mon Aug 27 10:52:50 2012 +0200

    Second revision

commit a7e25a158ce52a75c62381420f7dc375de631b1b
Author: Christophe Pallier <christophe@pallier.org>
Date:   Mon Aug 27 10:49:54 2012 +0200

    First revision; added readme2.txt

commit a7a3a47edfae9d7c720356b691000a81ded73906
Author: Christophe Pallier <christophe@pallier.org>
Date:   Mon Aug 27 10:47:32 2012 +0200

    First commit

Downloading the most recent changes from the distant repository

If you imported your repository from the internet with 'git clone', you can import the recent changes with:

$ git pull

Pushing your changes to the distant repository

You can send your modified repository (after commiting) to the original internet repository:

$ git push