devops-exercises/exercises/git/README.md

# Git

## Exercises

|Name|Topic|Objective & Instructions|Solution|Comments|
|--------|--------|------|----|----|
| My first Commit | Commit | [Exercise](exercises/git/commit_01.md) | [Solution](exercises/git/solutions/commit_01_solution.md) | |
| Time to Branch | Branch | [Exercise](exercises/git/branch_01.md) | [Solution](exercises/git/solutions/branch_01_solution.md) | |
| Squashing Commits | Commit | [Exercise](exercises/git/squashing_commits.md) | [Solution](exercises/git/solutions/squashing_commits.md) | |

## Questions

<details>
<summary>How do you know if a certain directory is a git repository?</summary><br><b>

You can check if there is a ".git" directory.
</b></details>

<details>
<summary>Explain the following: <code>git directory</code>, <code>working directory</code> and <code>staging area</code></summary><br><b>

This answer taken from [git-scm.com](https://git-scm.com/book/en/v1/Getting-Started-Git-Basics#_the_three_states)

"The Git directory is where Git stores the meta data and object database for your project. This is the most important part of Git, and it is what is copied when you clone a repository from another computer.

The working directory is a single checkout of one version of the project. These files are pulled out of the compressed database in the Git directory and placed on disk for you to use or modify.

The staging area is a simple file, generally contained in your Git directory, that stores information about what will go into your next commit. It’s sometimes referred to as the index, but it’s becoming standard to refer to it as the staging area."
</b></details>

<details>
<summary>What is the difference between <code>git pull</code> and <code>git fetch</code>?</summary><br><b>

Shortly, git pull = git fetch + git merge

When you run git pull, it gets all the changes from the remote or central
repository and attaches it to your corresponding branch in your local repository.

git fetch gets all the changes from the remote repository, stores the changes in
a separate branch in your local repository
</b></details>

<details>
<summary>How to check if a file is tracked and if not, then track it?</summary><br><b>

There are different ways to check whether a file is tracked or not:

  - `git ls-files <file>` -> exit code of 0 means it's tracked
  - `git blame <file>`
  ...
</b></details>

<details>
<summary>How can you see which changes have done before committing them?</summary><br><b>

`git diff```
</b></details>

<details>
<summary>What <code>git status</code> does?</summary><br><b>
</b></details>

### Branches

<details>
<summary>True or False? A branch is basically a simple pointer or reference to the head of certain line of work</summary><br><b>

True
</b></details>

<details>
<summary>You have two branches - main and devel. How do you make sure devel is in sync with main?</summary><br><b>

```
git checkout main
git pull
git checkout devel
git merge main
```
</b></details>

<details>
<summary>Describe shortly what happens behind the scenes when you run <code>git branch <BRANCH></code></summary><br><b>

Git runs update-ref to add the SHA-1 of the last commit of the branch you're on into the new branch you would like to create
</b></details>

<details>
<summary>When you run <code>git branch <BRANCH></code> how does Git know the SHA-1 of the last commit?</summary><br><b>

Using the HEAD file: `.git/HEAD`
</b></details>

<details>
<summary>True or False? when you <code>git checkout some_branch</code>, Git updates .git/HEAD to <code>/refs/heads/some_branch</code></summary><br><b>

True
</b></details>

### Merge

<details>
<summary>You have two branches - main and devel. How do you merge devel into main?</summary><br><b>

git checkout main
git merge devel
git push origin main
</b></details>

<details>
<summary>How to resolve git merge conflicts?</summary><br><b>

<p>
First, you open the files which are in conflict and identify what are the conflicts.
Next, based on what is accepted in your company or team, you either discuss with your
colleagues on the conflicts or resolve them by yourself
After resolving the conflicts, you add the files with `git add <file_name>`
Finally, you run `git rebase --continue`
</p>
</b></details>

<details>
<summary>What merge strategies are you familiar with?</summary><br><b>

Mentioning two or three should be enough and it's probably good to mention that 'recursive' is the default one.

recursive
resolve
ours
theirs

This page explains it the best: https://git-scm.com/docs/merge-strategies
</b></details>

<details>
<summary>Explain Git octopus merge</summary><br><b>

Probably good to mention that it's:

  * It's good for cases of merging more than one branch (and also the default of such use cases)
  * It's primarily meant for bundling topic branches together

This is a great article about Octopus merge: http://www.freblogg.com/2016/12/git-octopus-merge.html
</b></details>

<details>
<summary>What is the difference between <code>git reset</code> and <code>git revert</code>?</summary><br><b>

<p>

`git revert` creates a new commit which undoes the changes from last commit.

`git reset` depends on the usage, can modify the index or change the commit which the branch head
is currently pointing at.
</p>
</b></details>

### Rebase

<details>
<summary>You would like to move forth commit to the top. How would you achieve that?</summary><br><b>

Using the `git rebase` command
</b></details>

<details>
<summary>In what situations are you using <code>git rebase</code>?</summary><br><b>
</b></details>

<details>
<summary>How do you revert a specific file to previous commit?</summary><br><b>

```
git checkout HEAD~1 -- /path/of/the/file
```
</b></details>

<details>
<summary>How to squash last two commits?</summary><br><b>
</b></details>

<details>
<summary>What is the <code>.git</code> directory? What can you find there?</summary><br><b>
	The <code>.git</code> folder contains all the information that is necessary for your project in version control and all the information about commits, remote repository address, etc. All of them are present in this folder. It also contains a log that stores your commit history so that you can roll back to history.


This info copied from [https://stackoverflow.com/questions/29217859/what-is-the-git-folder](https://stackoverflow.com/questions/29217859/what-is-the-git-folder)
</b></details>

<details>
<summary>What are some Git anti-patterns? Things that you shouldn't do</summary><br><b>

  * Not waiting too long between commits
  * Not removing the .git directory :)
</b></details>

<details>
<summary>How do you remove a remote branch?</summary><br><b>

You delete a remote branch with this syntax:

git push origin :[branch_name]
</b></details>

<details>
<summary>Are you familiar with gitattributes? When would you use it?</summary><br><b>

gitattributes allow you to define attributes per pathname or path pattern.<br>

You can use it for example to control endlines in files. In Windows and Unix based systems, you have different characters for new lines (\r\n and \n accordingly). So using gitattributes we can align it for both Windows and Unix with `* text=auto` in .gitattributes for anyone working with git. This is way, if you use the Git project in Windows you'll get \r\n and if you are using Unix or Linux, you'll get \n.
</b></details>

<details>
<summary>How do you discard local file changes? (before commit)</summary><br><b>

`git checkout -- <file_name>`
</b></details>

<details>
<summary>How do you discard local commits?</summary><br><b>

`git reset HEAD~1` for removing last commit
If you would like to also discard the changes you `git reset --hard``
</b></details>

<details>
<summary>True or False? To remove a file from git but not from the filesystem, one should use <code>git rm </code></summary><br><b>

False. If you would like to keep a file on your filesystem, use `git reset <file_name>`
</b></details>

## References

<details>
<summary>How to list the current git references in a given repository? </summary><br><b>

`find .git/refs/`
</b></details>