Version Control With Git

# FAYA:80 Hand-On Git Workflow
.footnote[By [Rejah Rehim](https://rejahrehim.com)]
---

<img src="/images/fulls/git-diag.webp" alt="Introduction" style="min-width:200px; max-width:400px;"/>
# Version Controll with
<img src="/images/fulls/git.webp" alt="Git" style="min-width:100px; max-width:200px;"/>

---

# What is Git?

- Open-source code management tool

- Created by Linus Torvalds when he was building the Linux kernel.

- Git is DSCS (Distributed Source Control System)

- Git allows you to work on your code with the peace of mind that everything you do is reversible.

???

This means that even if you're using a centralized work-flow, every user essentially has a full backup of the main server. Each of these copies could be pushed up to replace the main server in the event of a crash or corruption. In effect, there is no single point of failure with Git unless there is only a single copy of the repository.

---
name: DISTRIBUTED
class: middle, center

# Why should i use git?

# ?

---

# BRANCHING AND MERGING

### Git allows and encourages you to have multiple local branches that can be entirely independent of each other.

- Frictionless Context Switching - Create a branch to try out an idea, commit a few times, switch back to where you branched from.

- Feature Based Work-flow - Create new branches for each new feature you're working on so you can seamlessly switch back and forth between them, then delete each branch when that feature gets merged into your main line.

- Disposable Experimentation - Create a branch to experiment in, realize it's not going to work, and just delete it - abandoning the work

---
name: DISTRIBUTED
class: middle, center

# DISTRIBUTED

### This means that even if you're using a centralized work-flow, every user essentially has a full backup of the main server. Each of these copies could be pushed up to replace the main server in the event of a crash or corruption. In effect, there is no single point of failure with Git unless there is only a single copy of the repository.

---
name: Staging
class: middle, center
# Staging Area

### Unlike the other systems, Git has something called the "staging area" or "index". This is an intermediate area where commits can be formatted and reviewed before completing the commit.
### It's possible to quickly stage some of your files and commit them without committing all of the other modified files in your working directory

???
Unlike the other systems, Git has something called the "staging area" or "index". This is an intermediate area where commits can be formatted and reviewed before completing the commit.

It's possible to quickly stage some of your files and commit them without committing all of the other modified files in your working directory

---
name: standard
class: middle, center
# GIT is new standard

---
name: standard
class: middle, center
# 2015
<img src="/images/fulls/git-2015.webp" alt="2015" style="min-width:200px; max-width:600px;"/>
---
name: standard
class: middle, center

# 2017
<img src="/images/fulls/git-2017.webp" alt="2017" style="min-width:200px; max-width:600px;"/>
---
name: standard
class: middle, center
# 2018
<img src="/images/fulls/git-2018.webp" alt="2018" style="min-width:200px; max-width:600px;"/>

---
name: standard
class: middle, center

# Install Git

## Installing on Linux

--
If you’re on Fedora (or any closely-related RPM-based distribution, such as RHEL or CentOS), you can use dnf:
```
$ sudo dnf install git-all
```
--
If you’re on a Debian-based distribution, such as Ubuntu, try apt:

```
$ sudo apt install git-all
```
---

## Installing on Mac

--
The easiest method is, install the Xcode Command Line Tools.

More up to date version, download at the Git website.

http://git-scm.com/download/mac.

---
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class: middle, center

## Installing on Windows
--

official build is available for download on the Git website. Just go to http://git-scm.com/download/win and the download

---
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class: middle, center

# Setup
<img src="/images/fulls/setup.webp" alt="2018" style="min-width:200px; max-width:200px;"/>

---
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class: middle, center

# Setup Name and Email

Run the following commands so that git knows
    - your name
    - your email

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

$ git config --global user.email "you@appfabs.com"
```
---
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class: middle, center

# Setup Line Ending Preferences

- Unix/Mac users:

```
$ git config --global core.autocrlf input

$ git config --global core.safecrlf true
```

- Windows users:

```
$ git config --global core.autocrlf true

$ git config --global core.safecrlf true
```

---
name: setup
class: middle, center

# SetUp Editor & Diff tool

```
$ git config --global core.editor emacs
```

- Another useful option you may want to configure is the default diff tool to use to resolve merge conflicts.

```
$ git config --global merge.tool vimdiff
```
---
name: setup
class: middle, center

# CREATE/CLONE A PROJECT

Create the Repository

```
$ git init
Initialized empty Git repository in /Users/rejah/working/directory/.git/
```

- Clone a Repository

```
$  git clone git@letzgame.com:testing.git

Cloning into 'testing'...
remote: Counting objects: 21, done.
remote: Compressing objects: 100% (17/17), done.
remote: Total 21 (delta 2), reused 0 (delta 0)
Receiving objects: 100% (21/21), 2.50 MiB, done.
Resolving deltas: 100% (2/2), done
```
---

# Add the program to the repository

```
$ git add hello.php
$ git commit -m "Add hellp.php to the repo"
[master (root-commit) 9416416] First Commit 1 files changed, 1 insertions(+), 0 deletions(-) create mode 100644 hello.php
```

---
name: add-program
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# Check the status of the repository

git status  to check the current status of the repo.

```
$ git status
# On branch master
nothing to commit (working directory clean)
```

```
$ git status
# On branch master
# Changes not staged for commit:
#   (use "git add ..." to update what will be committed)
#   (use "git checkout -- ..." to discard changes in working directory)
#
# modified:   hello.php
#
no changes added to commit (use "git add" and/or "git commit -a") 
```

---
name: add-program
class: middle, center

# staging Changes
```
$ git add hello.php
$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD ..." to unstage)
#
# modified:   hello.php
# 
```
The change to the hello.php file has been staged. This means that git now knows about the change, but the change hasn’t been permanently recorded in the repository yet. The next commit operation will include the staged changes.

???
If you decide you don’t want to commit that change after all, the status command reminds you that the git reset command can be used to unstage that change.

---
name: add-program
class: middle, center

# Staging and Committing

Suppose you edited three files (a.php, b.php, and c.php). Now you want to commit all the changes, but you want the changes in a.php and b.php to be a single commit, while the changes to c.php are not logically related to the first two files and should be a separate commit.

```
git add a.php

git add b.php

git commit -m "Add Changes for a and b"

git add c.php

git commit -m "Add Unrelated change to c"
```
By separating staging and committing, you have the ability to easily fine tune what goes into each commit.

---
name: add-program
class: middle, center

# Committing Changes

```
git commit 
```
You should see the following in your default editor:

```
|
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# On branch master
# Changes to be committed:
#   (use "git reset HEAD ..." to unstage)
#
# modified:   hello.php
#
```
On the first line, enter the comment: “Test Commit”. Save the file and exit the editor.
Provide Commit message
```
git commit -m "Test Commit"
```

---
name: add-program
class: middle, center

# Better commit message

---

- Separate subject from body with a blank line
--

- Limit the subject line to 50 characters

---

- Capitalize the subject line

For example:

Accelerate to 88 miles per hour

Instead of:

accelerate to 88 miles per hour

- Do not end the subject line with a period

Example:

Open the pod bay doors

Instead of:

Open the pod bay doors.

---

- Use the imperative mood in the subject line

That is as if you were commanding someone. Start the line with "Fix", "Add", "Change" instead of "Fixed", "Added", "Changed".
examples:
```
    refactor subsystem X for readability
```

Git commit subject line should always be able to complete the following sentence:

For example:

- If applied, this commit will refactor subsystem X for readability
 - If applied, this commit will update getting started documentation
 - If applied, this commit will merge pull request #123 from user/branch

Will not work in non-imperative forms:

- If applied, this commit will fixed bug with Y
 - If applied, this commit will changing behavior of X

---

- Wrap the body at 72 characters
--

- Use the body to explain what and why vs. how

This commit from Bitcoin Core is a great example:

```
commit eb0b56b19017ab5c16c745e6da39c53126924ed6
Author: Pieter Wuille <pieter.wuille@gmail.com>
Date: Fri Aug 1 22:57:55 2014 +0200

Simplify serialize.h's exception handling

Remove the 'state' and 'exceptmask' from serialize.h's stream
   implementations, as well as related methods.

As exceptmask always included 'failbit', and setstate was always
   called with bits = failbit, all it did was immediately raise an
   exception. Get rid of those variables, and replace the setstate
   with direct exception throwing (which also removes some dead
   code).

As a result, good() is never reached after a failure (there are
   only 2 calls, one of which is in tests), and can just be replaced
   by !eof().

fail(), clear(n) and exceptions() are just never called. Delete
   them.
```

???

If it seems difficult to summarize what your commit does, it may be because it includes several logical changes or bug fixes, and are better split up into several commits using git add -p.

---

Getting a listing of what changes have been made is the function of the git log command.
```
$ git log
commit 1f7ec5eaa8f37c2770dae3b984c55a1531fcc9e7
Author: Rejah 
Date:   Sat Apr 13 15:20:42 2013 -0400

Add a comment

commit 582495ae59ca91bca156a3372a72f88f6261698b
Author: Rejah 
Date:   Sat Apr 13 15:20:42 2013 -0400

Add a default value

```
---

# One Line Histories
```
$ git log --pretty=oneline
1f7ec5eaa8f37c2770dae3b984c55a1531fcc9e7 Add a comment
582495ae59ca91bca156a3372a72f88f6261698b Add a default value
323e28d99a07d404c04f27eb6e415d4b8ab1d615 Use ARGV for arg parsing
94164160adf8faa3119b409fcfcd13d0a0eb8020 inital Commit
```
--
# Controlling Which Entries are Displayed

You have a great deal of control over exactly what the log command displays.

```
git log --pretty=oneline --max-count=2

git log --pretty=oneline --since='5 minutes ago'

git log --pretty=oneline --until='5 minutes ago'

git log --pretty=oneline --author=

git log --pretty=oneline --all
```

---

# Getting Old Versions

```
$ git log --pretty=format:'%h %ad | %s%d [%an]' --graph --date=short
* 1f7ec5e 2013-09-13 | Add a comment (HEAD, master) [Rejah]
* 582495a 2013-09-13 | Add a default value [Rejah]
* 323e28d 2013-09-13 | Use ARGV [Rejah]
* 9416416 2013-09-13 | Inital Commit [Rejah]
```

```
$ git checkout 9416416
Note: checking out '9416416'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

git checkout -b new_branch_name

HEAD is now at 9416416... Inital Commit
```
---

# Return the latest version in the master branch

```
$ git checkout master
Previous HEAD position was 9416416... Inital Commit
Switched to branch 'master' 
```

---
name: add-program
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# Tagging

---
name: tagging
class: middle, center

# Tagging versions
```
$ git tag v1 
```
Now you can refer to the current version of the program as v1.
Checking Out by Tag Name
```
$ git checkout v1
Previous HEAD position was 582495a... Add a default value
HEAD is now at 1f7ec5e... Add a comment
$ git checkout v1-beta
Previous HEAD position was 1f7ec5e... Add a comment
HEAD is now at 582495a... Add a default value
```
---
name: tag-command
class: middle, center

# Viewing Tags using the tag command

```
$ git tag
v1
v1-beta
```

Viewing Tags in the Logs
```
$ git log --pretty=format:'%h %ad | %s%d [%an]' --graph --date=short master --all 
* 1f7ec5e 2013-04-13 | Add a comment (v1, master) [Jim Weirich] 
* 582495a 2013-04-13 | Add a default value (HEAD, v1-beta) [Jim Weirich] * 323e28d 2013-04-13 | Using ARGV [Jim Weirich] 
* 9416416 2013-04-13 | First Commit [Jim Weirich]
```
---
name: tag-command
class: middle, center

# Removing tag

```
$ git tag -d oops
Deleted tag 'oops' (was a10293f)

```
---
name: tag-command
class: middle, center

# UNDOING

---
name: tag-command
class: middle, center

# Local Changes (before staging)

Sometimes you have modified a file in your local working directory and you wish to just revert to what has already been committed. The checkout command will handle that.

```
git checkout hello.php

git status

vim hello.php
```
---
name: tag-command
class: middle, center

# Staged Changes (before committing)

```
$ git reset HEAD hello.php

Unstaged changes after reset:
M hello.php
```

The reset command resets the staging area to be whatever is in HEAD. This clears the staging area of the change we just staged.

The reset command (by default) doesn’t change the working directory. So the working directory still has the unwanted code in it.

---

# Undoing Committed Changes

Change that you have already committed was not correct and you wish to undo that commit.
```
$ git revert HEAD --no-edit
[master a10293f] Revert "Oops, we didn't want this commit" 1 files changed, 1 insertions(+), 1 deletions(-)
```
A revert operation will take the specified commit, inverse the changes from that commit, and create a new "revert commit".

```
$ git reset --hard v1
HEAD is now at 1f7ec5e Added a comment
$ git hist
* 1f7ec5e 2013-04-13 | Add a comment (HEAD, master) [Rejah]
* 582495a 2013-04-13 | Add a default value (v1-beta) [Rejah]
```

???
Since we were undoing the very last commit we made, we were able to use HEAD as the argument . We can revert any arbitrary commit earlier in history by simply specifying its hash value.

Note: The --no-edit in the output can be ignored. used to generate the output without opening the editor.

---
name: restting-vs-reverting
class: middle, center

# Resetting vs Reverting

---
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# Amending Commits

After you make the commit, you realize that any good author comment should have an email included. Update the hello program to include an email.

```
git add hello.php

git commit --amend -m "Add an author/email comment"
```

---
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# Branches

---
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# Create a Branch

```
$ git checkout -b greet

$ git status

```
 git checkout -b <branchname> is a shortcut for git branch <branchname> followed by a git checkout <branchname>.

---
name: restting-vs-reverting
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# Navigating Branches
```
$ git checkout master
Switched to branch 'master'
```

# Merge the branches
```
$ git merge master 
Merge made by recursive. README | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) 
create mode 100644 README 
```

---

# Resolving Conflicts

---
```
$ git checkout newbranch
Switched to branch 'newbranch'
$ git merge master
Auto-merging lib/hello.php
CONFLICT (content): Merge conflict in lib/hello.php
Automatic merge failed; fix conflicts and then commit the result.
```

If you open lib/hello.php, you will see:
```
<<<<<<< HEAD:mergetest 
This is my third line 
======= This is a fourth line I am adding 
>>>>>>> 4e2b407f501b68f8588aa645acafffa0224b9b78:mergetest 
```
<<<<<<<: Indicates the start of the lines that had a merge conflict. The first set of lines are the lines from the file that you were trying to merge the changes into.

=======: Indicates the break point used for comparison. Breaks up changes that user has committed (above) to changes coming from merge (below) to visually see the differences.

>>>>>>>: Indicates the end of the lines that had a merge conflict.
---

# How do I resolve a merge conflict in a file?

You resolve a conflict by editing the file to manually merge the parts of the file that git had trouble merging.

This may mean discarding either your changes or someone else's or doing a mix of the two.

You will also need to delete the <<<<<<<, =======, and >>>>>>> in the file. 
---
name: conflicts
class: middle, center

# What do I do after I've resolved conflicts in all affected files?

Commit the Conflict Resolution

git add the file(s)
```
$ git  add -A 
```

git commit and git push (Push only for branches tracked.)

```
$git commit -m "Resolve Conflict in merge A and B" 
$git push
```

---
# Using an external merge tool

- meld

---
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# What is Origin?

```
$ git remote
 origin 
```
We see that the cloned repository knows about a remote repository

```
$ git remote show origin

* remote origin
  Fetch URL: git@letzgame.com:testing.git
  Push  URL: git@letzgame.com:testing.git
  HEAD branch: master
  Remote branch:
    master tracked
  Local branch configured for 'git pull':
    master merges with remote master
  Local ref configured for 'git push':
    master pushes to master (up to date)
```

---
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# What is Origin?

Remote repositories typically live on a separate machine, possibly a centralized server.

There is nothing particularly special about the name “origin”, however the convention is to use the name “origin” for the primary centralized repository (if there is one).

---
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# Remote Branches

```
$ git branch 
* master
```

That’s it, only the master branch is listed.
 The git branch command only lists the local branches by default.

```
$ git branch -a
* master
  remotes/origin/HEAD -> origin/master
  remotes/origin/greet
  remotes/origin/master 
```
Git has all the commits from the original repository, but branches in the remote repository are not treated as local branches here. If we want our own , we need to create it ourselves.

---

#  Working With Remote

---
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# Adding a Remote Repository

Let’s add the testing.git repo to our original repo.
```
git remote add git@letzgame.com:testing.git 
```
Add a local branch that tracks a remote branch
```
$ git branch --track newbranch origin/greet
Branch newbranch set up to track remote branch newbranch from origin.
$ git branch -a
  newbranch
* master
  remotes/origin/HEAD -> origin/master
  remotes/origin/newbranch
  remotes/origin/master 
```
We can now see the greet branch in the branch list and in the log.

---

# Fetching Changes
```
$ git fetch
From /Users/jim/working/git/git_immersion/auto/hello 2fae0b2..2e4c559 master -> origin/master
```
The “git fetch” command will fetch new commits from the remote repository, but it will not merge these commits into the local branches.

# Merging Pulled Changes
```
$ git merge origin/master 
Updating 2fae0b2..2e4c559 Fast-forward README | 1 + 1 files changed, 1 insertions(+), 0 deletions(-)

```

---

# Pushing a Change
```
$ git push origin master
To git@letzgame.com:testing.git
 2e4c559..3923dd5  master -> master
```

---

# Pulling Change

We’re not going to go through the process of creating another change and pulling it again, but we do want you to know that doing:
```
$ git pull origin master
```
is indeed equivalent to the two steps:

```
$ git fetch

$ git merge origin/master
```
origin is the name of the repository receiving the changes we are pushing. (Remember, we added it as a remote)

---
name: restting-vs-reverting
class: middle, center

# Stash

When you’ve been working on part of your project, things are in a messy state and you want to switch branches for a bit to work on something else.
--
Put in stash: 
```
git stash save "Message"
```
--

Show stash: 
```
git stash list
```
--

Show stash stats: 
```
git stash show stash@{0}
```
--
Show stash changes:

```
git stash show -p stash@{0}
```
---

Use custom stash item and drop it:
```
git stash pop stash@{0}
```

Use custom stash item and do not drop it: 
```
git stash apply stash@{0}
```

Delete custom stash item:

```
git stash drop stash@{0}
```
--

Delete complete stash:

````
git stash clear
```

---
name: restting-vs-reverting
class: middle, center

# Gitignore & Gitkeep

--
There are files you don't want Git to track it

- Create a file in your repository named .gitignore
--

If you already have a file checked in, and you want to ignore it

```
git rm --cached FILENAME

```
--

Generate simple gitignore from 
<a href="https://www.gitignore.io/">https://www.gitignore.io/</a>

Track empty dir by putting .gitkeep file inside it

???

Ignored files are usually build artifacts and machine generated files that can be derived from your repository source or should otherwise not be committed. Some common examples are:

dependency caches, such as the contents of /node_modules or /packages
    compiled code, such as .o, .pyc, and .class files
    build output directories, such as /bin, /out, or /target
    files generated at runtime, such as .log, .lock, or .tmp
    hidden system files, such as .DS_Store or Thumbs.db
    personal IDE config files, such as .idea/workspace.xml

---
name: restting-vs-reverting
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# Compare

Compare modified files:

```
git diff
```

Compare modified files and highlight changes only:

```
git diff --color-words index.html
```

Compare modified files within the staging area:
```
git diff --stage
```

--
Compare modified files between two commits:

```
git diff  6eb715d 537a09f

```

---
name: restting-vs-reverting
class: middle, center

# Workflow

---

# Centralized Workflow
<img src="/images/fulls/centralized_workflow.webp" alt="centralized workflow" style="min-width:200px; max-width:600px;"/>

The centralized workflow. One central hub, or repository, can accept code, and everyone synchronizes their work to it

---

# Integration-Manager Workflow

- A contributor clones from the blessed repository and makes changes and push to their own public repo.

- The contributor sends the maintainer an email asking them to pull changes.

- The maintainer adds the contributor’s repository as a remote and merges locally.

- The maintainer pushes merged changes to the main repository

---

# Dictator and Lieutenants Workflow
<img src="/images/fulls/benevolent-dictator.webp" alt="benevolent dictator workflow" style="min-width:200px; max-width:400px;"/>

- Regular developers work on their topic branch and rebase their work on top of master. The master branch is that of the reference repository to which the dictator pushes.

- Lieutenants merge the developers' topic branches into their master branch.

- The dictator merges the lieutenants' master branches into the dictator’s master branch.

- Finally, the dictator pushes that master branch to the reference repository so the other developers can rebase on it.

---

# Branching Workflow

---

# Git-Flow Workflow

---
name: restting-vs-reverting
class: middle, center

# Decentralized but centralized

---
name: restting-vs-reverting
class: middle, center

# The main branches

The central repo holds two main branches with an infinite lifetime:

- master
- develop

---

# Supporting branches

The different types of branches are:

- Feature branches
- Release branches
- Hotfix branches

---

# Feature branches

---

# Hotfix branches

---
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# GitHub flow

- Create a branch from the repository.
- Create, edit, rename, move, or delete files.
- Send a pull request from your branch with your proposed changes to kick off a discussion.
- Make changes on your branch as needed. Your pull request will update automatically.
- Merge the pull request once the branch is ready to be merged.
- Tidy up your branches using the delete button in the pull request or on the branches page.

---
name: restting-vs-reverting
class: middle, center

# Thanks