We're still in our working directory:

In [1]:
import os
top_dir = os.getcwd()
git_dir = os.path.join(top_dir, 'learning_git')
working_dir = os.path.join(git_dir, 'git_example')

Sharing your work

So far, all our work has been on our own computer. But a big part of the point of version control is keeping your work safe, on remote servers. Another part is making it easy to share your work with the world In this example, we'll be using the "GitHub" cloud repository to store and publish our work.

If you have not done so already, you should create an account on GitHub: go to https://github.com/, fill in a username and password, and click on "sign up for free".

Creating a repository

Ok, let's create a repository to store our work. Hit "new repository" on the right of the github home screen, or click here.

Fill in a short name, and a description. Choose a "public" repository. Don't choose to add a Readme.

Paying for GitHub

For this course, you should use public repositories in your personal account for your example work: it's good to share! GitHub is free for open source, but in general, charges a fee if you want to keep your work private.

In the future, you might want to keep your work on GitHub private.

Students can get free private repositories on GitHub, by going to GitHub Education and filling in a form (look for the Student Developer Pack).

Adding a new remote to your repository

Instructions will appear, once you've created the repository, as to how to add this new "remote" server to your repository:

In [2]:
git remote add origin https://${GITHUB_TOKEN}@github.com/alan-turing-institute/github-example.git
In [3]:
git push -uf origin master # I have an extra `f` switch here.
      #You should copy the instructions from YOUR repository.
Branch 'master' set up to track remote branch 'master' from 'origin'.
To https://github.com/alan-turing-institute/github-example.git
 + b78ca30...03e1d59 master -> master (forced update)


The first command sets up the server as a new remote, called origin.

Git, unlike some earlier version control systems is a "distributed" version control system, which means you can work with multiple remote servers.

Usually, commands that work with remotes allow you to specify the remote to use, but assume the origin remote if you don't.

Here, git push will push your whole history onto the server, and now you'll be able to see it on the internet! Refresh your web browser where the instructions were, and you'll see your repository!

Let's add these commands to our diagram:

In [4]:
Working Directory -> Staging Area : git add
Staging Area -> Local Repository : git commit
Working Directory -> Local Repository : git commit -a
Staging Area -> Working Directory : git checkout
Local Repository -> Staging Area : git reset
Local Repository -> Working Directory: git reset --hard
Local Repository -> Remote Repository : git push
from wsd import wsd
%matplotlib inline

Playing with GitHub

Take a few moments to click around and work your way through the GitHub interface. Try clicking on 'index.md' to see the content of the file: notice how the markdown renders prettily.

Click on "commits" near the top of the screen, to see all the changes you've made. Click on the commit number next to the right of a change, to see what changes it includes: removals are shown in red, and additions in green.

Working with multiple files

Some new content

So far, we've only worked with one file. Let's add another:

vim lakeland.md
In [5]:
%%writefile lakeland.md
Cumbria has some pretty hills, and lakes too.  
Writing lakeland.md
In [6]:
cat lakeland.md
Cumbria has some pretty hills, and lakes too.  

Git will not by default commit your new file

In [7]:
git commit -am "Try to add Lakeland"
On branch master
Your branch is up to date with 'origin/master'.

Untracked files:

nothing added to commit but untracked files present
CalledProcessError                        Traceback (most recent call last)
<ipython-input-7-b38098616040> in <module>
----> 1 get_ipython().run_cell_magic('bash', '', 'git commit -am "Try to add Lakeland"\n')

~/virtualenv/python3.6.3/lib/python3.6/site-packages/IPython/core/interactiveshell.py in run_cell_magic(self, magic_name, line, cell)
   2321             magic_arg_s = self.var_expand(line, stack_depth)
   2322             with self.builtin_trap:
-> 2323                 result = fn(magic_arg_s, cell)
   2324             return result

~/virtualenv/python3.6.3/lib/python3.6/site-packages/IPython/core/magics/script.py in named_script_magic(line, cell)
    140             else:
    141                 line = script
--> 142             return self.shebang(line, cell)
    144         # write a basic docstring:

<decorator-gen-109> in shebang(self, line, cell)

~/virtualenv/python3.6.3/lib/python3.6/site-packages/IPython/core/magic.py in <lambda>(f, *a, **k)
    185     # but it's overkill for just that one bit of state.
    186     def magic_deco(arg):
--> 187         call = lambda f, *a, **k: f(*a, **k)
    189         if callable(arg):

~/virtualenv/python3.6.3/lib/python3.6/site-packages/IPython/core/magics/script.py in shebang(self, line, cell)
    243             sys.stderr.flush()
    244         if args.raise_error and p.returncode!=0:
--> 245             raise CalledProcessError(p.returncode, cell, output=out, stderr=err)
    247     def _run_script(self, p, cell, to_close):

CalledProcessError: Command 'b'git commit -am "Try to add Lakeland"\n'' returned non-zero exit status 1.

This didn't do anything, because we've not told git to track the new file yet.

Tell git about the new file

In [8]:
git add lakeland.md
git commit -am "Add lakeland"
[master 86cf371] Add lakeland
 1 file changed, 4 insertions(+)
 create mode 100644 lakeland.md

Ok, now we have added the change about Cumbria to the file. Let's publish it to the origin repository.

In [9]:
git push
To https://github.com/alan-turing-institute/github-example.git
   03e1d59..86cf371  master -> master

Visit GitHub, and notice this change is on your repository on the server. We could have said git push origin to specify the remote to use, but origin is the default.

Changing two files at once

What if we change both files?

In [10]:
%%writefile lakeland.md
Cumbria has some pretty hills, and lakes too

* Helvellyn
Overwriting lakeland.md
In [11]:
%%writefile index.md
Mountains and Lakes in the UK   
Engerland is not very mountainous.
But has some tall hills, and maybe a
mountain or two depending on your definition.
Overwriting index.md
In [12]:
git status
On branch master
Your branch is up to date with 'origin/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:   index.md
	modified:   lakeland.md

Untracked files:
  (use "git add <file>..." to include in what will be committed)


no changes added to commit (use "git add" and/or "git commit -a")

These changes should really be separate commits. We can do this with careful use of git add, to stage first one commit, then the other.

In [13]:
git add index.md
git commit -m "Include lakes in the scope"
[master b5f225b] Include lakes in the scope
 1 file changed, 4 insertions(+), 3 deletions(-)

Because we "staged" only index.md, the changes to lakeland.md were not included in that commit.

In [14]:
git commit -am "Add Helvellyn"
[master 563f95e] Add Helvellyn
 1 file changed, 4 insertions(+), 1 deletion(-)
In [15]:
git log --oneline
563f95e Add Helvellyn
b5f225b Include lakes in the scope
86cf371 Add lakeland
03e1d59 Revert "Add a lie about a mountain"
d4a9132 Change title
cb67f8a Add a lie about a mountain
a2f6abf First commit of discourse on UK topography
In [16]:
git push
To https://github.com/alan-turing-institute/github-example.git
   86cf371..563f95e  master -> master
In [17]:
participant "Jim's remote" as M
participant "Jim's repo" as R
participant "Jim's index" as I
participant Jim as J

note right of J: vim index.md
note right of J: vim lakeland.md

note right of J: git add index.md
J->I: Add *only* the changes to index.md to the staging area

note right of J: git commit -m "Include lakes"
I->R: Make a commit from currently staged changes: index.md only

note right of J: git commit -am "Add Helvellyn"
J->I: Stage *all remaining* changes, (lakeland.md)
I->R: Make a commit from currently staged changes

note right of J: git push
R->M: Transfer commits to Github