Sync local rep and GitHub

Overview

Teaching: 30 min
Exercises: 0 min

Questions

• How do I work with a local and a remote repository?

Objectives

• Explain what remote repositories are and why they are useful.

• Push to or pull from a remote repository.

Our remote repository and our local repository are different. We have made changes to our local repository and want to update GitHub. This command will push the changes from our local repository to the repository on GitHub:

$ git push origin master

Counting objects: 3, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 318 bytes | 0 bytes/s, done.
Total 3 (delta 2), reused 0 (delta 0)
remote: Resolving deltas: 100% (2/2), completed with 2 local objects.
To https://github.com/username/GRAD521_DMPSurname_2019.git
   873b2a1..1c2321f  master -> master

Our local and remote repositories are now in this state:

Navigate to GitHub and check the index.md and the commits listed. You should see the changes we just worked on from our local repository.

The information can go both ways, we can also change the documents in GitHub and transfer the changes to our local computer. Let’s make a change again in GitHub.

$ git pull origin master

remote: Enumerating objects: 5, done.
remote: Counting objects: 100% (5/5), done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 3 (delta 1), reused 0 (delta 0), pack-reused 0
Unpacking objects: 100% (3/3), done.
From https://github.com/clarallebot/GRAD521_DMPtemplate
 * branch            master     -> FETCH_HEAD
   c3279ca..949e394  master     -> origin/master
Merge made by the 'recursive' strategy.
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Version control really comes into its own when we begin to collaborate with other people. Systems like Git allow us to move work between any two repositories. In practice, though, it’s easiest to use one copy as a central hub, and to keep it on the web rather than on someone’s laptop. Most programmers use hosting services like GitHub, BitBucket or GitLab to hold those master copies; we’ll explore the pros and cons of this in the final section of this lesson.

Proxy

If the network you are connected to uses a proxy there is an chance that your last command failed with “Could not resolve hostname” as the error message. To solve this issue you need to tell Git about the proxy:

$ git config --global http.proxy http://user:password@proxy.url
$ git config --global https.proxy http://user:password@proxy.url

When you connect to another network that doesn’t use a proxy you will need to tell Git to disable the proxy using:

$ git config --global --unset http.proxy
$ git config --global --unset https.proxy

Password Managers

If your operating system has a password manager configured, git push will try to use it when it needs your username and password. For example, this is the default behavior for Git Bash on Windows. If you want to type your username and password at the terminal instead of using a password manager, type:

$ unset SSH_ASKPASS

in the terminal, before you run git push. Despite the name, git uses SSH_ASKPASS for all credential entry, so you may want to unset SSH_ASKPASS whether you are using git via SSH or https.

You may also want to add unset SSH_ASKPASS at the end of your ~/.bashrc to make git default to using the terminal for usernames and passwords.

GitHub GUI

Browse to your GRAD521_DMPSurname_2019 repository on GitHub. Under the Code tab, find and click on the text that says “XX commits” (where “XX” is some number). Hover over, and click on, the three buttons to the right of each commit. What information can you gather/explore from these buttons? How would you get that same information in the shell?

GitHub Timestamp

Create a remote repository on GitHub. Push the contents of your local repository to the remote. Make changes to your local repository and push these changes. Go to the repo you just created on Github and check the timestamps of the files. How does GitHub record times, and why?

Push vs. Commit

In this lesson, we introduced the “git push” command. How is “git push” different from “git commit”?

GitHub License and README files

In this section we learned about creating a remote repository on GitHub, but when you initialized your GitHub repo, you didn’t add a README.md or a license file. If you had, what do you think would have happened when you tried to link your local and remote repositories?

Key Points

• A local Git repository can be connected to one or more remote repositories.

• git push copies changes from a local repository to a remote repository.

• git pull copies changes from a remote repository to a local repository.