Using Git

Basics
Adding and Changing Things
Undo Changes and Recover Files
Viewing Commits
Branch and Merge
Commands for Remotes
Favorites
Resources

Note on Paths

In this file, directory paths are written with a forward slash as on MacOS, Linux, and the Windows-Bash shell: /dir1/dir2/somefile.

Basics

1. When using Git locally, what are these? Define each one in a sentence

   • Staging area - Prepare the changes that will be reflected on the next commit (index).
   • Working copy - It is a state where the source code is being changed or modified.
   • master - Initial default branch.
   • HEAD - Last commit in the current branch.

2. When you install git on a new machine (or in a new user account) you should perform these 2 git commands to tell git your name and email. These values are used in commits that you make:

   git config --global user.name <name>
   git donfig --global user.email <email>
   

3. There are 2 ways to create a local Git repository. Briefly describe each one:

   • git init (Create a new git repository)
   • git clone <url> (copy of that repository at in a new directory)

Adding and Changing Things

Suppose your working copy of a repository contains these files and directories:

README.md
out/
    a.exe
src/a.py
    b.py
    c.py
test/
    test_a.py
    ...

1. Add README.md and everything in the src directory to the git staging area.

   git add README.md
   git add src/
   

2. Add test/test_a.py to the staging area (but not any other files).

   git add test/test_a.py
   

3. List the names of files in the staging area.

   git status
   

4. Remove README.md from the staging area. This is very useful if you accidentally add something you don't want to commit.

   git rm README.md
   

5. Commit everything in the staging area to the repository.

   git commit -m "msg"
   

6. In any project, there are some files and directories that you should not commit to git.
   For a Python project, name at least files or directories that you should not commit to git:

   • .idea
   • pycache
   • venv

7. Command to move all the .py files from the src dir to the top-level directory of this repository. This command moves them in your working copy and in the git repo (when you commit the change):

   git mv src/*.py .
   

8. In this repository, create your own .gitignore file that you can reuse in other Python projects. Add everything that you think is relevant.
   Hint: A good place to start is to create a new repo on Github and during the creation dialog, ask Github to make a .gitignore for Python projects. Then edit it. Don't forget to include pytest output and MacOS junk.

   touch .gitignore
   

Undo Changes and Recover Files

1. Display the differences between your working copy of a.py and the a.py in the local repository (HEAD revision):

git diff a.py HEAD

2. Display the differences between your working copy of a.py and the version in the staging area. (But, if a.py is not in the staging area this will compare working copy to HEAD revision):

   git diff a.py
   

3. View changes to be committed: Display the differences between files in the staging area and the versions in the repository. (You can also specify a file name to compare just one file.)

   git diff --staged
   

4. Undo "git add": If main.py has been added to the staging area (git add main.py), remove it from the staging area:

   git reset HEAD main.py
   

   or

   git restore --staged main.py
   

5. Recover a file: Command to replace your working copy of a.py with the most recent (HEAD) version in the repository. This also works if you have deleted your working copy of this file.

   git checkout HEAD a.py
   

6. Undo a commit: Suppose you want to discard some commit(s) and move both HEAD and "master" to an earlier revision (an earlier commit) Suppose the git commit graph looks like this (aaaa, etc, are the commit ids)

   aaaa ---> bbbb ---> cccc ---> dddd [HEAD -> master]

   git reset bbbb
   

   The command to reset HEAD and master to the commit id bbbb:

7. Checkout old code: Using the above example, the command to replace your working copy with the files from commit with id aaaa:

   git checkout aaaa
   

   Note:

   • Git won't let you do this if you have uncommitted changes to any "tracked" files.
   • Untracked files are ignored, so after doing this command they will still be in your working copy.

Viewing Commits

1. Show the history of commits, using one line per commit:

   git log --oneline
   

   Some versions of git have an alias "log1" for this (git log1).

2. Show the history (as above) including all branches in the repository and include a graph connecting the commits:

   git log --oneline --decorate --graph --all
   

3. List all the files in the current branch of the repository:

   git ls-tree --name-only HEAD
   

   Example output:

   .gitignore
   README.md
   a.py
   b.py
   test/test_a.py
   test/test_b.py
   

Branch and Merge

1. Local branch with a specific remote branch and creating a tracking relationship.

git branch -u origin/main <branch>      

2. Moving a branch reference to a specific commit ID.

git branch -f <branch> <commit-id>

3. Merge branches with no fast forward.

git merge --no-ff <branch>

4. To see the last commit on each branch.

git branch -v

Favorites

Task Viewing Adding and Changing Things problem (7) : A helpful tool for efficiently organizing files within a Git repository

Task Viewing Commits problem (3) : In my exploration of Git, I've discovered 'git ls-tree' command. It allows me to easily see what each commit contains in terms of files and directories.

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Resources

• Basic Git Basic Git Command in Thai language.

• Basic Video Git Video the basic Git Command in Thai language.

• git ls-tree Command git ls-tree Command Example. Allows you to list the contents of a tree object.

• Git Remote Add a new remote, use the git remote add command on the terminal.

• Git Remote Origin(URL) Change Git Remote Origin Using SSH URL.

• Pro Git Online Book Chapters 2 & 3 contain the essentials. Downloadable e-book is available, too.

• Visual Git Reference one page with illustrations of git commands.

• Markdown Cheatsheet summary of Markdown commands.

• Github Markdown some differences in the way Github handles markdown and special Markdown for repos.

Learn Git Visually:

• Learn Git Interactive Tutorial great visual tutorial
• Git Visualizer execute Git commands in a web browser and see the results as a graph.