4.4 Collaboration
Contents
4.4 Collaboration#
Estimated time to complete this notebook: 20 minutes
Form a team#
Now we’re going to get to the most important question of all with Git and GitHub: working with others.
Organise into pairs. You’re going to be working on the website of one of the two of you, together, so decide who is going to be the leader, and who the collaborator.
Giving permission#
The leader needs to let the collaborator have the right to make changes to his code.
In GitHub, go to Settings on the right, then Collaborators & teams on the left.
Add the user name of your collaborator to the box. They now have the right to push to your repository.
Obtaining a colleague’s code#
Next, the collaborator needs to get a copy of the leader’s code. For this example notebook, I’m going to be collaborating with myself, swapping between my two repositories. Make yourself a space to put it your work. (I will have two)
import os
top_dir = os.getcwd()
git_dir = os.path.join(top_dir, "learning_git")
working_dir = os.path.join(git_dir, "git_example")
os.chdir(git_dir)
%%bash
pwd
rm -rf github-example # cleanup after previous example
rm -rf partner_dir # cleanup after previous example
/home/runner/work/rse-course/rse-course/module04_version_control_with_git/learning_git
Next, the collaborator needs to find out the URL of the repository: they should go to the leader’s repository’s GitHub page, and note the URL on the top of the screen.
As before, we’re using SSH to connect - to do this you’ll need to make sure the ssh button is pushed, and check that the URL begins with git@github.com.
Copy the URL into your clipboard by clicking on the icon to the right of the URL, and then:
%%bash
pwd
git clone git@github.com:alan-turing-institute/github-example.git partner_dir
/home/runner/work/rse-course/rse-course/module04_version_control_with_git/learning_git
Cloning into 'partner_dir'...
partner_dir = os.path.join(git_dir, "partner_dir")
os.chdir(partner_dir)
%%bash
pwd
ls
/home/runner/work/rse-course/rse-course/module04_version_control_with_git/learning_git/partner_dir
lakeland.md
test.md
Note that your partner’s files are now present on your disk:
%%bash
cat lakeland.md
Lakeland
========
Cumbria has some pretty hills, and lakes too
Mountains:
* Helvellyn
Nonconflicting changes#
Now, both of you should make some changes. To start with, make changes to different files. This will mean your work doesn’t “conflict”. Later, we’ll see how to deal with changes to a shared file.
Both of you should commit, but not push, your changes to your respective files:
E.g., the leader:
os.chdir(working_dir)
%%writefile Wales.md
Mountains In Wales
==================
* Tryfan
* Yr Wyddfa
Writing Wales.md
%%bash
ls
Wales.md
__pycache__
lakeland.md
test.md
wsd.py
%%bash
git add Wales.md
git commit -m "Add wales"
[main 79f56b9] Add wales
1 file changed, 5 insertions(+)
create mode 100644 Wales.md
And the partner:
os.chdir(partner_dir)
%%writefile Scotland.md
Mountains In Scotland
==================
* Ben Eighe
* Cairngorm
Writing Scotland.md
%%bash
ls
Scotland.md
lakeland.md
test.md
%%bash
git add Scotland.md
git commit -m "Add Scotland"
[main c5d6b91] Add Scotland
1 file changed, 5 insertions(+)
create mode 100644 Scotland.md
One of you should now push with git push:
%%bash
git push
To github.com:alan-turing-institute/github-example.git
7267535..c5d6b91 main -> main
Rejected push#
The other should then attempt to push, but should receive an error message:
os.chdir(working_dir)
%%bash
git push || echo "Push failed"
To github.com:alan-turing-institute/github-example.git
! [rejected] main -> main (fetch first)
error: failed to push some refs to 'github.com:alan-turing-institute/github-example.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.
Push failed
Do as it suggests:
%%bash
git pull
From github.com:alan-turing-institute/github-example
7267535..c5d6b91 main -> origin/main
* [new branch] experiment -> origin/experiment
Merge made by the 'ort' strategy.
Scotland.md | 5 +++++
1 file changed, 5 insertions(+)
create mode 100644 Scotland.md
Merge commits#
A window may pop up with a suggested default commit message. This commit is special: it is a merge commit. It is a commit which combines your collaborator’s work with your own.
Now, push again with git push. This time it works. If you look on GitHub, you’ll now see that it contains both sets of changes.
%%bash
git push
To github.com:alan-turing-institute/github-example.git
c5d6b91..f8080e1 main -> main
The partner now needs to pull down that commit:
os.chdir(partner_dir)
%%bash
git pull
From github.com:alan-turing-institute/github-example
c5d6b91..f8080e1 main -> origin/main
Updating c5d6b91..f8080e1
Fast-forward
Wales.md | 5 +++++
1 file changed, 5 insertions(+)
create mode 100644 Wales.md
%%bash
ls
Scotland.md
Wales.md
lakeland.md
test.md
Nonconflicted commits to the same file#
Go through the whole process again, but this time, both of you should make changes to a single file, but make sure that you don’t touch the same line. Again, the merge should work as before:
%%writefile Wales.md
Mountains In Wales
==================
* Tryfan
* Snowdon
Overwriting Wales.md
%%bash
git diff
diff --git a/Wales.md b/Wales.md
index f3e88b4..90f23ec 100644
--- a/Wales.md
+++ b/Wales.md
@@ -2,4 +2,4 @@ Mountains In Wales
==================
* Tryfan
-* Yr Wyddfa
+* Snowdon
%%bash
git commit -am "Translating from the Welsh"
[main 970500e] Translating from the Welsh
1 file changed, 1 insertion(+), 1 deletion(-)
%%bash
git log --oneline
970500e Translating from the Welsh
f8080e1 Merge branch 'main' of github.com:alan-turing-institute/github-example
79f56b9 Add wales
c5d6b91 Add Scotland
7267535 Add Helvellyn
bb45a08 Include lakes in the scope
35a257c Add lakeland
65ba0b3 Revert "Add a lie about a mountain"
e6c8259 Change title
589000c Add a lie about a mountain
bb05a4f First commit of discourse on UK topography
os.chdir(working_dir)
%%writefile Wales.md
Mountains In Wales
==================
* Pen y Fan
* Tryfan
* Yr Wyddfa
Overwriting Wales.md
%%bash
git commit -am "Add a beacon"
[main 153e1b1] Add a beacon
1 file changed, 1 insertion(+)
%%bash
git log --oneline
153e1b1 Add a beacon
f8080e1 Merge branch 'main' of github.com:alan-turing-institute/github-example
79f56b9 Add wales
c5d6b91 Add Scotland
7267535 Add Helvellyn
bb45a08 Include lakes in the scope
35a257c Add lakeland
65ba0b3 Revert "Add a lie about a mountain"
e6c8259 Change title
589000c Add a lie about a mountain
bb05a4f First commit of discourse on UK topography
%%bash
git push
To github.com:alan-turing-institute/github-example.git
f8080e1..153e1b1 main -> main
Switching back to the other partner…
os.chdir(partner_dir)
%%bash
git push || echo "Push failed"
To github.com:alan-turing-institute/github-example.git
! [rejected] main -> main (fetch first)
error: failed to push some refs to 'github.com:alan-turing-institute/github-example.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.
Push failed
%%bash
git pull
From github.com:alan-turing-institute/github-example
f8080e1..153e1b1 main -> origin/main
Auto-merging Wales.md
Merge made by the 'ort' strategy.
Wales.md | 1 +
1 file changed, 1 insertion(+)
%%bash
git push
To github.com:alan-turing-institute/github-example.git
153e1b1..79a3294 main -> main
%%bash
git log --oneline --graph
* 79a3294 Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * 153e1b1 Add a beacon
* | 970500e Translating from the Welsh
|/
* f8080e1 Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * c5d6b91 Add Scotland
* | 79f56b9 Add wales
|/
* 7267535 Add Helvellyn
* bb45a08 Include lakes in the scope
* 35a257c Add lakeland
* 65ba0b3 Revert "Add a lie about a mountain"
* e6c8259 Change title
* 589000c Add a lie about a mountain
* bb05a4f First commit of discourse on UK topography
os.chdir(working_dir)
%%bash
git pull
From github.com:alan-turing-institute/github-example
153e1b1..79a3294 main -> origin/main
Updating 153e1b1..79a3294
Fast-forward
Wales.md | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
%%bash
git log --graph --oneline
* 79a3294 Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * 153e1b1 Add a beacon
* | 970500e Translating from the Welsh
|/
* f8080e1 Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * c5d6b91 Add Scotland
* | 79f56b9 Add wales
|/
* 7267535 Add Helvellyn
* bb45a08 Include lakes in the scope
* 35a257c Add lakeland
* 65ba0b3 Revert "Add a lie about a mountain"
* e6c8259 Change title
* 589000c Add a lie about a mountain
* bb05a4f First commit of discourse on UK topography
message = """
participant Sue as S
participant "Sue's repo" as SR
participant "Shared remote" as M
participant "Jim's repo" as JR
participant Jim as J
note left of S: git clone
M->SR: fetch commits
SR->S: working directory as at latest commit
note left of S: edit Scotland.md
note right of J: edit Wales.md
note left of S: git commit -am "Add scotland"
S->SR: create commit with Scotland file
note right of J: git commit -am "Add wales"
J->JR: create commit with Wales file
note left of S: git push
SR->M: update remote with changes
note right of J: git push
JR-->M: !Rejected change
note right of J: git pull
M->JR: Pull in Sue's last commit, merge histories
JR->J: Add Scotland.md to working directory
note right of J: git push
JR->M: Transfer merged history to remote
"""
from wsd import wsd
%matplotlib inline
wsd(message)
Conflicting commits#
Finally, go through the process again, but this time, make changes which touch the same line.
%%writefile Wales.md
Mountains In Wales
==================
* Pen y Fan
* Tryfan
* Snowdon
* Fan y Big
Overwriting Wales.md
%%bash
git commit -am "Add another Beacon"
git push
[main 5187cad] Add another Beacon
1 file changed, 1 insertion(+)
To github.com:alan-turing-institute/github-example.git
79a3294..5187cad main -> main
os.chdir(partner_dir)
%%writefile Wales.md
Mountains In Wales
==================
* Pen y Fan
* Tryfan
* Snowdon
* Glyder Fawr
Overwriting Wales.md
%%bash
git commit -am "Add Glyder"
[main 2218446] Add Glyder
1 file changed, 1 insertion(+)
%%bash
git push || echo "Push failed"
To github.com:alan-turing-institute/github-example.git
! [rejected] main -> main (fetch first)
error: failed to push some refs to 'github.com:alan-turing-institute/github-example.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.
Push failed
When you pull, instead of offering an automatic merge commit message, it says:
%%bash
git pull || echo "Pull failed"
From github.com:alan-turing-institute/github-example
79a3294..5187cad main -> origin/main
Auto-merging Wales.md
CONFLICT (content): Merge conflict in Wales.md
Automatic merge failed; fix conflicts and then commit the result.
Pull failed
Resolving conflicts#
Git couldn’t work out how to merge the two different sets of changes.
You now need to manually resolve the conflict.
It has marked the conflicted area:
%%bash
cat Wales.md
Mountains In Wales
==================
* Pen y Fan
* Tryfan
* Snowdon
<<<<<<< HEAD
* Glyder Fawr
=======
* Fan y Big
>>>>>>> 5187cad95966e5b0330566d0279058a99793c47f
Manually edit the file, to combine the changes as seems sensible and get rid of the symbols:
%%writefile Wales.md
Mountains In Wales
==================
* Pen y Fan
* Tryfan
* Snowdon
* Fan y Big
* Glyder Fawr
Overwriting Wales.md
Commit the resolved file#
Now commit the merged result:
%%bash
git commit -a --no-edit # I added a No-edit for this non-interactive session. You can edit the commit if you like.
[main 1acc420] Merge branch 'main' of github.com:alan-turing-institute/github-example
%%bash
git push
To github.com:alan-turing-institute/github-example.git
5187cad..1acc420 main -> main
os.chdir(working_dir)
%%bash
git pull
From github.com:alan-turing-institute/github-example
5187cad..1acc420 main -> origin/main
Updating 5187cad..1acc420
Fast-forward
Wales.md | 1 +
1 file changed, 1 insertion(+)
%%bash
cat Wales.md
Mountains In Wales
==================
* Pen y Fan
* Tryfan
* Snowdon
* Fan y Big
* Glyder Fawr
%%bash
git log --oneline --graph
* 1acc420 Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * 5187cad Add another Beacon
* | 2218446 Add Glyder
|/
* 79a3294 Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * 153e1b1 Add a beacon
* | 970500e Translating from the Welsh
|/
* f8080e1 Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * c5d6b91 Add Scotland
* | 79f56b9 Add wales
|/
* 7267535 Add Helvellyn
* bb45a08 Include lakes in the scope
* 35a257c Add lakeland
* 65ba0b3 Revert "Add a lie about a mountain"
* e6c8259 Change title
* 589000c Add a lie about a mountain
* bb05a4f First commit of discourse on UK topography
Distributed VCS in teams with conflicts#
message = """
participant Sue as S
participant "Sue's repo" as SR
participant "Shared remote" as M
participant "Jim's repo" as JR
participant Jim as J
note left of S: edit the same line in wales.md
note right of J: edit the same line in wales.md
note left of S: git commit -am "update wales.md"
S->SR: add commit to local repo
note right of J: git commit -am "update wales.md"
J->JR: add commit to local repo
note left of S: git push
SR->M: transfer commit to remote
note right of J: git push
JR->M: !Rejected
note right of J: git pull
M->J: Make conflicted file with conflict markers
note right of J: edit file to resolve conflicts
note right of J: git add wales.md
note right of J: git commit
J->JR: Mark conflict as resolved
note right of J: git push
JR->M: Transfer merged history to remote
note left of S: git pull
M->SR: Download Jim's resolution of conflict.
"""
wsd(message)
The Levels of Git#
message = """
Working Directory -> Staging Area : git add
Staging Area -> Local Repository : git commit
Local Repository -> Local Repository : git commit -a
Local Repository -> Working Directory : git checkout
Local Repository -> Staging Area : git reset
Local Repository -> Working Directory: git reset --hard
Local Repository -> Remote Repository : git push
Remote Repository -> Local Repository : git fetch
Local Repository -> Working Directory : git merge
Remote Repository -> Working Directory: git pull
"""
wsd(message)
Editing directly on GitHub#
Note that you can also make changes in the GitHub website itself. Visit one of your files, and hit “edit”.
Make a change in the edit window, and add an appropriate commit message.
That change now appears on the website, but not in your local copy. (Verify this).
Now pull, and check the change is now present on your local version.