[testcase notes] #2: two developers work on the same branch simultaneously (same file, diff lines)

[dorawyy]

Cloned the repo twice and commit in each repo to simulate two developers working on the same branch

Scenario abstraction

• developer1 and developer2 worked on the same repo, same branch(TestA branch in this case);
• They cloned the remote repo:
  • developer1 --> repo1
  • developer2 --> repo2
• developer1 edited testcase2 file line2, add, commit;
• developer2 edited testcase2 file line5, add, commit;
• developer1 pushed the commit to remote repo TestA branch;
• what would happen if developer2 pushed directly now?

Results:

• developer2 failed git push, got notification to git pull first;
• when git pull, auto-merging, with an extra merge commit (though no conflict, still three-way merging);
• the merge commit is created on repo2, repo2 TestA branch head in the merge commit;
• developer1 git pull now, fast-forward

Data could be explored:

• a merge commit and its parents commits SHA

Detailed steps

step0: start point of the test case:

• created the file testcase2 on TestA branch working as the start point of the testcase (SHA``)

Step1: cloned two repos ( already did in testcase #1 )

git clone https://github.com/dorawyy/git-merge-conflicts-test.git git-merge-conflicts-test-1
git clone https://github.com/dorawyy/git-merge-conflicts-test.git git-merge-conflicts-test-2

To make it short, we call them:

• repo1
• repo2

Step2: developer1 committed in repo1, TestA branch (SHA``)

• Developer1 edited testcase2 file line10 in repo1 TestA branch

  

• git add, git commit, no push yet

git add --testcase2
git commit -m "TestA: developer1 edited line2 of file"

and git log of the file testcase2 after commits

Step3: developer2 committed in repo2, TestA branch (SHA``)

• Developer2 edited testcase2 file line5 in repo2 TestA branch

  

• git add, git commit, no push yet

git add --all
git commit -m "TestA: developer2 edited line8 of file testcase2"

Step4: developer1 pushed commit on repo1 back to remote repo

# make sure on TestA branch
git branch 
# push change back to remote
git push origin TestA

When logging back to remote repo(on github), we can see the commit pushed by developer1 just now:

Step5: developer2 tried pushing commits from repo2 back to remote repo (without pulling first)

# make sure on TestA branch
git branch
# push change back
git push origin TestA

It turned out pushing failed, git required us to pull first. The tree of repo2 has not changed till now.

Step6: developer2 git pull from repo2 TestA branch

Therefore, we git pull first to get all changes locally

git branch
git pull origin TestA 

As developer1 and developer2 committed on different lines of the same file, no conflict raised. However, it is still three-way merging, with an extra merge commit.. As the screenshot above shows, when git pull, create a merge commit.

Step7: developer2 pushed commit from repo2 to the remote repo.

git push origin TestA

Now, we can see commits from github side

Step9: developer1 git pull, check git tree and git log

git pull origin TestA
git tree 
git log

The git tree and git log look like: (exactly the same as repo2)

Data explored here, the merge commit will list the two parent commits as the picture above shows