Reproducible Research 3 - Git: 2 devs and a central repository
Wojciech Hardy
link: https://hackmd.io/@WHardy/RR25-git2
How does it work? (quick recap)
Cheatsheet: Basic commands
Cheatsheet: Advanced commands
Git commands: working with a central repository
git init --bare to create barebones for a central repository (with no initial commits)
git clone [repo_name] [clone_name] to create a linked copy of the repo_name repository.
git fetch grab information about new commits/branches from the central repository.
git pull to grab the (new) commits from the central repository to our repository.
git push to put our (newly created) commits in the central repository.
We're going to pretend we have two developers and a central repository.
Quick recap
-
In our workspace, let's create a new folder RR_git2 and go inside
-
Let's create a repository named RecapRepo and go inside
-
Change local user.name to "RecapRepoUser"
- Create three files: commit the first; only stage the second; do nothing to the third
-
In RR_git2 create a clone of the first repository; go inside
-
View the contents; check the status
-
View the
configfile in the.gitfolder.
(e.g. in notepad)
Exercise 5: simulating central repo with two locals
We're now going to pretend we have two people collaborating, using a central repository to manage the workflow.
- In your RR_git2 directory create a new, bare repository called "CentralRepo"
(Remember to use the appropriate option when initiating the repository!)
cd RR_git2
git init --bare CentralRepo
- In your RR_git2 directory create a clone of the CentralRepo, named Dev1
git clone CentralRepo Dev1
- In your RR_git2 directory create a clone of the CentralRepo, named Dev2
git clone CentralRepo Dev2
- Set the local
user.namefor Dev1 repository to "Developer_1"
cd Dev1
git config --local user.name "Developer_1"
- Set the local
user.namefor Dev2 repository to "Developer_2"
cd ../Dev2
git config --local user.name "Developer_2"
We'll be imitating this:
So far all repositories are empty. Let's imagine:
- Dev1 kick-starts the project by creating the branch with one commit and sending it
upstream
echo "This will be the file with code" > code.R
git add .
git commit -m "Added the file with code"
git status
git push
git status
- Dev2 wants to get up-to-speed so grabs the changes
git pull
Exercise 6: fetching and updating before pushing
As you go, try to remember what are the states of the Dev1, the Dev2 and the Central Repositories at each step. (You can even draw them)
- Create a readme.txt file in your Dev1 repository.
cd ../Dev1
touch readme.txt
- Stage, commit and push the file.
git add .
git commit -m "Added readme.txt"
git push
- Go to the Dev2 repository.
cd ../Dev2
- Run
git status
git status
- Fetch information about changes from the central repository. Run
git status.
git fetch
git status
- Pull the information. Check folder contents.
git pull
ls
- Add a new line to readme.txt and create a readme.md file.
echo "second line of text" >> readme.txt
touch readme.md
- Stage, commit and push the file to the central repository.
git add .
git commit -m "Added readme.md and changed readme.txt"
git push
- In Dev1, create a text3.txt file with the line "A line added by Dev1". Stage, commit and push - what happens? Resolve the issue following the hints.
cd ../Dev1
echo "A line added by Dev1" > text3.txt
git add .
git commit -m "Added text3"
git push
Follow the instructions from Git to resolve merge conflicts.
Exercise 7: a merge conflict
In Exercise 6 we had a divergence, but without a conflict (commits differed, but there were no conflicting changes to files).
What if two devs make two different versions of a file?
- In Dev2, create a new file called text3.txt with the line "A line added by Dev2". Stage, commit and try to push. Read the hints, follow and go to step 2.
- There's a conflict because Dev1 committed a different text3.txt file earlier.
We're in a merging mode. We can edit the file (e.g. in Notepad) to figure out what should remain. Then stage it and commit it.
The merge becomes a new commit (try git log)
Assignment
While still in your Dev2 repository, run these three commands:
git status > git2_a.txt
git log >> git2_a.txt
git ls-files >> git2_a.txt
Send me the notepad file git2_a.txt (wojciechhardy@uw.edu.pl).
Stuck in VIM?
If you forgot about adding a message to your commit, you might have ended up in VIM. It's a free, text-editting software that sometimes feels like a trap.
Tl;dr: hit [ESC], then type *:q * and press Enter .
Repeat your commit with a helpful description.
You can also try adding the comment in VIM instead, and then exit with :wq instead, which should do the commit with the comment.
See more in this helpful Stackoverflow answer.
Useful links
Read more on the three trees with the git reset guideline
If you need more, just Google tutorials/blog posts/YouTube videos until you find one that makes it clear :) Lots to choose from!