Add basics material

Author: mbaraa

material/02-basics.md

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+# Git basics
+
+Make sure that you have `git` installed on your machine, if not, refer to [this](/material/01-installation.md) page.
+
+## Initializing repositories
+
+### What is a Git repository?
+
+A Git repository is a directory containing all of a project's files, and it is managed by Git, where you can see a `.git` directory in **all** Git repositories, this directory allows Git to keep track of each file's revision history, and other Git data like branches and merges.
+
+### Initializing in the same directory (folder)
+
+To initialize Git in an existing project, go to that project's directory and run the command
+
+```bash
+git init
+```
+
+This will create the `.git` directory allowing Git to keep track of your files' changes.
+
+### Initializing into a new directory (folder)
+
+To a Git managed project, run the following command
+
+```bash
+git init <directory-name>
+```
+
+This will create a new directory with the specified name with `.git` directory inside of it allowing Git to keep track of your files' changes.
+
+### Cloning an existing repository
+
+Since Git is a distributed version controlling system, repositories may exist on some remote host like GitHub, Gitlab, or Bitbucket.
+
+For example cloning this repository
+
+```bash
+git clone https://github.com/jordanopensource/git-training
+```
+
+This will create a new directory named `git-training` with the content of the clone repository's files.
+
+### Forking a repository
+
+Forking; and its name gives it away, it's making a fork, like road forks, where a main road is forked side road(s), and evantually it looks like an eating fork, the same concept applied to Git repositories, where there's a main branch (road) on a repository, and you create a fork branch (side road) of it.
+
+All Git hosts support forking a public repository, where you copy the repository into your account or organization.
+
+## Staging and commits
+
+Each file in a Git repository goes throgh the four Git file stages:
+
+- **Untracked**: The file is newly created or moved from another directory to a Git directory, and Git doesn't keep any track of it.
+- **Unmodified**: The file is tracked by Git, i.e has been commited before, and has no new changes.
+- **Modified**: An uncommited file that has been modified but not committed yet.
+- **Staged**: A modified file that has been added to be commited.
+
+Here's a figure showing the relations between the four stages.
+![git files stages](/resourses/git-files-stages.png)
+
+### Commiting a file
+
+After creating a file (untracked) or editing an existing one (unmodified), you can add the file to the staging area, by running this command.
+
+```bash
+git add <file-name>
+```
+
+Or using this command to add all of the files in the current directory.
+
+```bash
+git add .
+```
+
+Now to move the file into the unmodified stage, commit the file with a commit message
+
+> Commit messages should describe what happened to a file, in an imperative way
+> e.g "Create <file-name>"
+
+```bash
+git commit -m "Create <file-name>"
+```
+
+Now the file that you have just commited is in the unmodified stage, where if you made a new modification to it it will get moved to the modified stage, and the cycle continues...
+
+### Discarding changes done after a commit
+
+If you modified a file, after a commit, and then realized that the changes weren't needed, you can rollback to the latest tracked version by Git, by running the following command.
+
+```bash
+git checkout -- <file-name>
+```
+
+## Pushing and Pulling
+
+## Understanding status and logs