git-commands: A repository from tnnpp

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

When using Git locally, what are these? Define each one in a sentence
- Staging area - middle ground between what you have done to your files.
- Working copy - active project folder that contain all file and changes that have made.
- master - main version of project.
- HEAD - pointer to the current checked out branch or commit.
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 configuration commands for a new account

git config --global user.name "Your Name"

git config --global user.email "youremail@example.com"
```
There are 2 ways to create a local Git repository. Briefly descibe each one:
- First way : Initialize in an existing directory
  1. Open the command line
  2. Go to the directory where you want to create repository
  3. Run the command
```
git init
```
  4. Adding file to the repository and commits
- Second way : Cloning a repository
  1. Copy URL of the repository you want to clone
  2. Open the command line
  3. Go to the directory where you want to create repository
  4. Run the command
```
git clone <repository_url>
```

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
    ...

Add README.md and everything in the src directory to the git staging area.
```
git add README.md
git add src/
```
Add test/test_a.py to the staging area (but not any other files).
```
git add test/test_a.py
```
List the names of files in the staging area.
```
git diff --cached --name-only 
```
Remove README.md from the staging area. This is very useful if you accidentally add something you don't want to commit.
```
git reset README.md
```
Commit everything in the staging area to the repository.
```
git commit -m "commit message"
```
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:
- Virtual Environment Directory:
- Dependency Management Files:
- Compiled or Generated Files
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 .
```
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.

Undo Changes and Recover Files

Display the differences between your working copy of a.py and the a.py in the local repository (HEAD revision): git diff a.py
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 --staged a.py
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 <filename>
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 main.py
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 -- a.py
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 cccc
```
The command to reset HEAD and master to the commit id bbbb:
```
git reset bbbb
```
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

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).
Show the history (as above) including all branches in the repository and include a graph connecting the commits:
```
git log --all --graph --oneline --decorate
```

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

git ls-tree --name-only -r HEAD

Example output:

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

Branch and Merge

create a branch

git branch <branch's name>

check what is the current branch

git branch

merge the branch

git merge <branch>

check which file are un merged

git status

Favorites

To integrate changes from one branch onto another branch

git rebase <branch's name>

Resources

Gihub cheat sheet summarize of Github's basic
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.

tnnpp/git-commands