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 16f7517] 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 7b72dce] 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
ef29071..7b72dce 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 not
hint: have locally. This is usually caused by another repository pushing to
hint: the same ref. If you want to integrate the remote changes, use
hint: '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
ef29071..7b72dce 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
7b72dce..2ed3750 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
7b72dce..2ed3750 main -> origin/main
Updating 7b72dce..2ed3750
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 e41e48f] Translating from the Welsh
1 file changed, 1 insertion(+), 1 deletion(-)
%%bash
git log --oneline
e41e48f Translating from the Welsh
2ed3750 Merge branch 'main' of github.com:alan-turing-institute/github-example
16f7517 Add wales
7b72dce Add Scotland
ef29071 Add Helvellyn
9cba9c4 Include lakes in the scope
bd7c0f2 Add lakeland
43f3942 Revert "Add a lie about a mountain"
ee151c1 Change title
da208a3 Add a lie about a mountain
973ce32 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 a0e175d] Add a beacon
1 file changed, 1 insertion(+)
%%bash
git log --oneline
a0e175d Add a beacon
2ed3750 Merge branch 'main' of github.com:alan-turing-institute/github-example
16f7517 Add wales
7b72dce Add Scotland
ef29071 Add Helvellyn
9cba9c4 Include lakes in the scope
bd7c0f2 Add lakeland
43f3942 Revert "Add a lie about a mountain"
ee151c1 Change title
da208a3 Add a lie about a mountain
973ce32 First commit of discourse on UK topography
%%bash
git push
To github.com:alan-turing-institute/github-example.git
2ed3750..a0e175d 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 not
hint: have locally. This is usually caused by another repository pushing to
hint: the same ref. If you want to integrate the remote changes, use
hint: '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
2ed3750..a0e175d 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
a0e175d..7375d5c main -> main
%%bash
git log --oneline --graph
* 7375d5c Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * a0e175d Add a beacon
* | e41e48f Translating from the Welsh
|/
* 2ed3750 Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * 7b72dce Add Scotland
* | 16f7517 Add wales
|/
* ef29071 Add Helvellyn
* 9cba9c4 Include lakes in the scope
* bd7c0f2 Add lakeland
* 43f3942 Revert "Add a lie about a mountain"
* ee151c1 Change title
* da208a3 Add a lie about a mountain
* 973ce32 First commit of discourse on UK topography
os.chdir(working_dir)
%%bash
git pull
From github.com:alan-turing-institute/github-example
a0e175d..7375d5c main -> origin/main
Updating a0e175d..7375d5c
Fast-forward
Wales.md | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
%%bash
git log --graph --oneline
* 7375d5c Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * a0e175d Add a beacon
* | e41e48f Translating from the Welsh
|/
* 2ed3750 Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * 7b72dce Add Scotland
* | 16f7517 Add wales
|/
* ef29071 Add Helvellyn
* 9cba9c4 Include lakes in the scope
* bd7c0f2 Add lakeland
* 43f3942 Revert "Add a lie about a mountain"
* ee151c1 Change title
* da208a3 Add a lie about a mountain
* 973ce32 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 7a1335d] Add another Beacon
1 file changed, 1 insertion(+)
To github.com:alan-turing-institute/github-example.git
7375d5c..7a1335d 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 bdb0127] 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 not
hint: have locally. This is usually caused by another repository pushing to
hint: the same ref. If you want to integrate the remote changes, use
hint: '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
7375d5c..7a1335d 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
>>>>>>> 7a1335db020d01c6c03ab35a3d3e4bec06d32c0e
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 b14af2b] Merge branch 'main' of github.com:alan-turing-institute/github-example
%%bash
git push
To github.com:alan-turing-institute/github-example.git
7a1335d..b14af2b main -> main
os.chdir(working_dir)
%%bash
git pull
From github.com:alan-turing-institute/github-example
7a1335d..b14af2b main -> origin/main
Updating 7a1335d..b14af2b
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
* b14af2b Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * 7a1335d Add another Beacon
* | bdb0127 Add Glyder
|/
* 7375d5c Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * a0e175d Add a beacon
* | e41e48f Translating from the Welsh
|/
* 2ed3750 Merge branch 'main' of github.com:alan-turing-institute/github-example
|\
| * 7b72dce Add Scotland
* | 16f7517 Add wales
|/
* ef29071 Add Helvellyn
* 9cba9c4 Include lakes in the scope
* bd7c0f2 Add lakeland
* 43f3942 Revert "Add a lie about a mountain"
* ee151c1 Change title
* da208a3 Add a lie about a mountain
* 973ce32 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.