hmc-cs121-admin / merging-pulling-exercise

Merge conflict, pull request, and how to resolve the conflict

Merging/Pulling Exercise

Prerequisites

(from https://github.com/StoneyJackson/github-workflow-activity/blob/rewrite/reference.md)

• You have a GitHub account and you know your username and password. If you don't have one, create one now.
• You have Git 2+ installed and configured.
• You know how to open a terminal and generally work from the command-line.
• You know enough of vi or vim to edit, move around in, save, and quit files.

Learning Objectives

When you finish this exercise, you will be able to...

• Fork a repository you would like to contribute to
• Clone a forked repository to your local hard drive
• Create a new branch (via CLI and GitHub web interface)
• Make a pull request
• Resolve merge conflicts

Instructor:

• Creates a (public) repository
• Add an initial README.md
• Add an initial rainbow.md containing color names
• Share the github repo URL with the students
• Show pull requests and accept PRs

Students:

Note: lines starting with [GitHub] should be done through GitHub's web interface.

Get Ready (fork and clone)

• [GitHub] Fork the instructor's repo (<ORIGINAL_REPOSITORY_URL>) to your GitHub account

• [GitHub] Navigate to your fork of the project. Use "Clone or download" to reveal your fork's repository URL. This is the <FORKED_REPOSITORY_URL>.

• Clone the forked repository to your local hard drive:

  git clone <FORKED_REPOSITORY_URL> <LOCAL_REPOSITORY_DIRECTORY>

Make a change to your local file (rainbow.md)

• cd to the new directory you just cloned

  cd <LOCAL_REPOSITORY_DIRECTORY>

• Create a new branch and check out the branch to make a change. Call your branch: <color-your_first_name-branch>, for example:

  git checkout -b red-firstname-branch

  (Specifying -b causes a new branch to be created as if git-branch were called and then checked out.)

Let's edit rainbow.md to add you color and name to it using your favorite text editor.

• Add your name to the list: list your first name underneath your favorite color, for example, under the Red section,

  red-firstname

• Save and exit. You may now try git status to see the rainbow.md was modified but not added.

• Stage your changes to your local git repository (add):

  git add rainbow.md

• Save your changes to your local repo (commit):

  git commit -m "added my color and name"

  (The "added my color and name" part is a commit message. When you commit, you should always give a meaningful message showing what's done and changed.)

Push your changes to a GitHub repo

• Now you can push the changes to your GitHub repo (the forked one)

  git push

  (Notice that you get a fatal error, for example:

  fatal: The current branch green-jeho has no upstream branch. To push the current branch and set the remote as upstream, use

  git push --set-upstream origin green-jeho

  The error is self-explanatory; your branch has no upstream branch. At this point, you basically have two options:

  (1) set upstream (i.e., origin) for your current branch (i.e., <<color-firstname-branch>>):

  git push --set-upstream origin <<color-firstname-branch>>

  (2) merge (fast-forward merge) your branch into master branch and push the new change to origin from the master branch:

  • Change branch to master (whose origin is already known)

    git checkout master

  • Merge <<color-firstname-branch>> into master branch

    git merge <<color-firstname-branch>> (After this point, your master branch and <> will be pointing to the same status; you can delete <> afterwards if you want as follows.)

  • Delete old branch (optional)

    git branch -d <<color-firstname-branch>>

  • Finally, you are ready to push the chages recorded in master branch to your (forked) GitHub repo:

    git push (this will upload all the new/updated files to the gitHub repo pointed as origin)

Create a Pull Request into the original instructor's repo

You're ready to create a PR (Pull Request)

• [GitHub] Pick a volunteer and let him/her make a pull request to the instructor's repo. (Notice that GitHub checks the original (instructor's) repo and reports whether the changes conflict or not.)

• In the main repo, the instructor merges the new change into master by approving the PR.

• Everyone should now sync their (forked) repo. See https://help.github.com/articles/syncing-a-fork/

• Note that people who selected the same color should now see a merge conflict.

• In case there's a conflict, you should resolve the conflict by opening the issue and change the file.

Resolve the merge conflict

• Pick another volunteer with the same color and they can now commit their branch and submit a PR.

• Let the second person (with the same color) resolve the conflict.

• Repeat the above steps to integrate the new change.

• Other volunteers with different colors should now submit their changes, call pull requests, and experience merge conflicts.

A Workflow considering GitHub web interface and local command line interface

Remote (GitHub) Web Interface	Local Command Line Interface
Create a GitHub repo	---
Fork a repo	(possible with hub)
(not possible)	Clone the remote (GitHub) repo to local repo
(possible)	Create/checkout new branches
(possible)	Create/edit files
---	Stage (add) the files
---	Commit the changes to local repo
(add/commit/push all at once)	Push the files to a remote (GitHub) repo
Pull request	(possible)
Resolve conflicts	(possible)