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<!doctype html>
<html lang="en">
<head>
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<title> A practical introduction to git</title>
<meta name="author" content="Anna Kennedy">
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<div class="reveal">
<div class="slides">
<!-- Title slide -->
<section>
<h1>A practical introduction to git</h1>
<p>
<small>Anna Kennedy</small>
</p>
<aside class="notes">
Some notes here
</aside>
</section>
<!-- Overview -->
<section>
<h1>Overview</h1>
<p class="fragment"><ul>
<li>Version control</li>
<li>Git concepts</li>
<li>Using git locally</li>
<li>Using git with a (Gitlab) remote</li>
<li>Undoing mistakes</li>
<li>Branches</li>
<li>Caring for your commit history</li>
</ul></p>
<aside class="notes">
</aside>
</section>
<!-- Version control -->
<section>
<h1>Version control</h1>
<p class="fragment"><ul>
<li><b>Version control</b> means that we keep a history of all the changes made in a set of documents.</li>
<li>Git is one example of a <b>version control</b> system<br/></li><br/>
<li>Pre-version control:
<ul>
<li>Copy file1 to file1.bak</li>
</ul>
</li>
<li>CVS / SVN:
<ul>
<li>Centralised storage with revision history</li>
</ul>
</li>
<li>Git:
<ul>
<li>Distributed system</li>
</ul>
</li>
</ul></p>
</section>
<section>
<h2>SVN</h2>
<p>Centralised storage with revision history</p>
<p class="fragment"><ul>
<li>client-server model</li>
<li>central server houses master repo</li>
<li>developer laptop is the client</li>
<li>check-out -> modify -> check-in</li><br/>
<li>Advantages / disadvantages</li>
<li>+ simple system</li>
<li>- difficult to work offline</li>
<li>- difficult to work collaboratively</li>
<li>- advanced functionality quite hard to get right</li>
</ul></p>
</section>
<section>
<h2>Git</h2>
<p>Distributed version control</p>
<p class="fragment"><ul>
<li>every copy of the project is a full repository</li><br/>
<li>Advantages / disadvantages</li>
<li>- steep learning curve</li>
<li>+ save changes locally when working offline</li>
<li>+ branching</li>
<li>+ merging</li>
<li>+ every copy is a full backup</li>
<li>+ very fast</li>
</ul></p>
</section>
<!-- Using git locally -->
<section>
<h1>Using git locally</h1>
</section>
<section>
<h3>Projects in git</h3>
<p><ul>
<li>Any directory can be brought under git's control</li>
<ul><li>both new and existing projects</li></ul><br/>
<li><b>git init</b> initialises a directory with a .git subdir</li>
<ul>
<li>This directory is now a <b>local git repository</b></li>
<li>The .git folder contains metadata about the project</li>
<li>To remove a project from git, simply delete the .git folder</li>
</ul>
</ul></p>
</section>
<section>
<h3>Exercise: Initialise a new project in git</h3>
<p><ul>
<li>Make a new directory and move into it</li>
<li>Initialise the directory as a git repository</li>
</ul>
<pre><code>
$ mkdir myproject
$ cd myproject
$ git init
Initialized empty Git repository in /home/myname/projects/myproject
$ ls -la
drwxr-xr-x 4096 Apr 5 09:54 .
drwxr-xr-x 4096 Apr 4 12:40 ..
drwxr-xr-x 4096 Apr 5 08:13 .git
</code></pre>
</p>
</section>
<section>
<h3>Configure global git variables</h3>
<p><ul>
<li>Git requires that version history is associated with users</li>
<li>Thus we need to set name and email as global variables</li>
<li>Trying to use git without this results in the following annoying message:</li>
</ul>
<pre><code>
Your name and email address were configured automatically based
on your username and hostname. Please check that they are accurate.
You can suppress this message by setting them explicitly:
$ git config --global user.name "Your Name"
$ git config --global user.email you@example.com
</code></pre>
</p>
</section>
<section>
<h3>Exercise: Check / set your name and email settings</h3>
<p><ul>
<li>Use <b>git config -l</b> to see if you've already set your name and email address</li>
<li>If you need to set them, use</li>
</ul>
<pre><code>
$ git config --global user.name "Your Name"
$ git config --global user.email you@example.com
</code></pre>
</p>
</section>
<section>
<h3>Checking the current status</h3>
<p><ul>
<li>Running <b>git status</b> at any point shows the current state of the directory</li>
<li>It also often gives hints about how to proceed or undo steps</li>
</ul>
<pre><code>
$ git init
Initialized empty Git repository in /home/myname/projects/myproject
$ git status
On branch master
Initial commit
nothing to commit (create/copy files and use "git add" to track)
</code></pre>
</p>
</section>
<section>
<h3>Getting help</h3>
<p><ul>
<li>Access the man pages on the command-line like:</li>
</ul>
<pre><code>
$ git help
The most commonly used git commands are:
add Add file contents to the index
branch List, create, or delete branches
checkout Checkout a branch or paths to the working tree
$ git help add
NAME
git-add - Add file contents to the index
SYNOPSIS
git add [-n] [-v] [-f] [-i] [-p] [--] [<pathspec>...]
</code></pre>
</p>
</section>
<section>
<h3>Adding files to the project</h3>
<p><ul>
<li><b>git add <i>filename</i></b> to add files to staging</li>
<li><b>git add .</b> to add everything</li>
</ul></p>
</section>
<section>
<h3>Exercise: Add files to the project</h3>
<p><ul>
<li>Make a file inside the directory "helloworld.txt"</li>
<li>Add this file to git</li></ul>
<pre><code>
$ vim helloworld.txt
$ git status
On branch master
Untracked files:
(use "git add file..." to include in what will be committed)
helloworld.txt
$ git add helloworld.txt
$ git status
On branch master
Changes to be committed:
(use "git reset HEAD file..." to unstage)
new file: helloworld.txt
</code></pre>
</p>
</section>
<section>
<h3>Committing the changes to the local repo</h3>
<p><ul>
<li>After a file is added to staging, we then have to commit the changes</li>
<li><b>git commit</b> and then enter commit message on the next screen</li>
<li><b>git commit -m <i>"commit message"</i></b> to do both steps at once</li>
</ul></p>
</section>
<section>
<h3>Exercise: Commit the changes to your local repo</h3>
<p><ul>
<li>Commit this file to your local repository</li>
<p><pre><code>
$ git commit -m "First commit"
$ git status
On branch master
nothing to commit, working directory clean
</code></pre></p>
</ul></p>
</section>
<section>
<h3>Basic git rhythm</h3>
<p><ul>
<li>Make changes</li>
<li>Stage the changes with <b>git add</b></li>
<li>Commit the changes with <b>git commit</b></li>
</ul></p>
</section>
<section>
<h3>View commit history</h3>
<p><ul>
<li><b>git log</b> shows a history of commits</li>
<li><b>git log -p</b> shows what has changed with each commit</li>
<li><b>git log -2</b> only shows the last two commits</li>
</ul></p>
<p><pre><code>
$ git log -p
commit 320a8f00a4a0de7c9b3f39851d3bc164d0769697
Author: myname myname@ak-rl.example.com
Date: Mon Apr 4 12:52:23 2016 +0200
First commit
diff --git a/file1.txt b/file1.txt
new file mode 100644
index 0000000..907b308
--- /dev/null
+++ b/file1.txt
@@ -0,0 +1 @@
+Hello everyone!
</code></pre></p>
</ul></p>
</section>
<section>
<h3>A little more about commits</h3>
<p><ul>
<li>Commits are basically snapshots</li>
<li>Each commit is identified by a unique hash</li>
<li>The most recent commit is called HEAD</li>
<li>The two before that are called HEAD~ and HEAD~2</li>
<li>We can use both the reference number and the HEAD notation to refer to previous commits</li>
</ul></p>
<p><pre><code>
$ git log
commit 320a8f00a4a0de7c9b3f39851d3bc164d0769697
Author: myname myname@ak-rl.example.com
Date: Mon Apr 4 12:52:23 2016 +0200
First commit
</code></pre></p>
</section>
<section>
<h3>Amend the commit message</h3>
<p><ul>
<li>If you accidentally did a commit with a mistake in the commit message</li>
<li><b>git commit --amend</b> lets you change it </li>
</ul></p>
</section>
<section>
<h3>Exercise: Edit your most recent commit</h3>
<p><ul>
<li>Edit your most recent commit message</li>
<p><pre><code>
$ git commit --amend
</code></pre>
<pre><code>
Allow user login
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
</code></pre></p>
</ul></p>
</section>
<section>
<h3>Exercise: Make and view a more interesting commit history</h3>
<p><ul>
<li>So far we literally only have one commit - let's make a bit more to work with</li>
<li>Make two more files, and commit them</li>
<li>Edit one file, and commit that</li>
<li>Make two files and only commit one of them</li>
<li>Now commit the other one</li>
<li>Use <b>git log</b> and <b>git status</b> to follow the history as you go</li>
</ul></p>
</section>
<section>
<h3>Comparing files</h3>
<p><ul>
<li><b>git diff</b> compares current files with the latest committed version</li>
<li>After you've made a change to a file, but before it's committed</li>
<li>Use 'git diff' to see what the difference between the files is</li>
</ul></p>
<p><pre><code>
$ echo "Pleased to meet you all." >> helloworld.txt
$ git diff
diff --git a/file1.txt b/file1.txt
index 404c772..2d48565 100644
--- a/file1.txt
+++ b/file1.txt
@@ -1,2 +1,3 @@
Hello everyone!
+Pleased to meet you all.
</code></pre></p>
</ul></p>
</section>
<section>
<h3>Exercise: Compare files</h3>
<p><ul>
<li>Make a change to a file</li>
<li>Use 'git diff' to see what the difference between the file now and the last committed version</li>
</ul></p>
<p><pre><code>
$ git diff
diff --git a/file1.txt b/file1.txt
index 404c772..2d48565 100644
--- a/file1.txt
+++ b/file1.txt
@@ -1,2 +1,3 @@
Hello everyone!
+Pleased to meet you all.
</code></pre></p>
</ul></p>
</section>
<section>
<h3>Stashing your work</h3>
<p><ul>
<li>We like to try and keep our commits meaningful (more on this later)</li>
<li>but if you're in the middle of working on something and you need to pause or switch branches</li>
<li>you can save your work-in-progress state with <b>git stash</b></li>
<li>Can stash multiple events</li>
<li><b>git stash list</b> to view them</li>
<li><b>git stash apply</b> to pick up your most recent stash</li>
</ul></p>
</section>
<section>
<h3>Exercise: Stashing your work</h3>
<p><ul>
<li>Make some changes to a file</li>
<li>Stash your changes</li>
<li>View the stash list</li>
<li>Verify the directory is at the state of the latest commit</li>
<li>Apply the stash to regain your work in progress</li>
</ul></p>
<p><pre><code>
$ git stash
Saved working directory and index state WIP on master: e99a3ac Allow user login
HEAD is now at e99a3ac Latest hegnar configs
$ git stash list
stash@{0}: WIP on master: e99a3ac Allow user login
</code></pre></p>
</section>
<!-- Using git with a remote -->
<section>
<h1>Using git with <br/>a remote</h1>
</section>
<section>
<h3>Using a remote repository</h3>
<p><ul>
<li>So far we only used our local repository</li>
<li>If we're interested in collaboration or backups, we need to look at communicating with a remote repository</li><br/>
<li>For this course, our remote is housed in Gitlab</li>
<li>Otherwise the remote could be</li>
<ul>
<li>plain git</li>
<li>gitolite</li>
<li>Gitorious</li>
<li>Github</li>
</ul>
</ul></p>
</section>
<section>
<h2>Gitlab</h2>
<p><ul>
<li>Gitlab provides a web-gui frontend</li>
<li>Lots of useful collaborative and exploratory features</li>
</ul>
<p><img width="450" src="img/gitlab.png" alt="gitlab"></p>
</section>
<section>
<h3>Creating a remote in Gitlab</h3>
<p>
<ul>
<li>Pretty straightforwards to create a new remote in Gitlab</li>
</ul>
<img width="950" src="img/gitlab_newproject.png" alt="gitlab"></p>
</section>
<section>
<h3>Exercise: Create a new remote repository</h3>
<p><ul>
<li>Within the Gitlab UI, make a new project</li>
<li>Name your project, leave it as private</li>
<li>Notice that it tells you how to proceed!</li>
<li>Within your local repository, tell git where the remote is:</li></ul>
<pre><code>
$ git remote add origin git@gitlab.example.com:myname/myprojectname.git
# Set a new remote
</code></pre>
</p>
</section>
<section>
<h3>Pushing changes from the local to the remote repo</h3>
<p>
<ul>
<li>So far all our work is only in our local repository</li>
<li>Use <b>git push</b> to send our commits to the remote repository</li>
<li>The first time we do this we need to set the upstream branch</li>
<li><b>origin</b> is git's default name for the remote repo</li>
</ul>
<pre><code>
$ git push -u origin master
Counting objects: 5, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (5/5), done.
Writing objects: 100% (5/5), 721 bytes | 0 bytes/s, done.
Total 5 (delta 2), reused 0 (delta 0)
To git@gitlab.example.com:myname/myproject.git
e99a3ac..f91ed8c master -> master
</code></pre>
</p>
</section>
<section>
<h3>Exercise: Push changes from the local to the remote repo</h3>
<p>
<ul>
<li>Use <b>git push</b> to send your commits to the remote repository</li>
<li>The first time we do this we need to set the upstream branch with -u</li>
<li>You should see your files in Gitlab now</li>
</ul>
<pre><code>
$ git push -u origin master
Counting objects: 5, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (5/5), done.
Writing objects: 100% (5/5), 721 bytes | 0 bytes/s, done.
Total 5 (delta 2), reused 0 (delta 0)
To git@gitlab.example.com:myname/myproject.git
e99a3ac..f91ed8c master -> master
</code></pre>
</p>
</section>
<section>
<h3>Retrieving changes from the remote</h3>
<p><ul>
<li>If changes have been made on the remote, we need to update our local repository to get those changes</li>
<li>Use <b>git pull</b> to retrieve any changes</li>
</ul></p>
</section>
<section>
<h3>Exercise: pulling remote changes</h3>
<p class="fragment"><ul>
<li>Edit a file in Gitlab</li>
<li>Pulled the changes your local repository</li>
<li>What do <b>git status</b> and <b>git log</b> say?</li></ul>
<pre><code>
$ git pull
remote: Counting objects: 3, done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 3 (delta 2), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
From gitlab.example.com:myname/myproject
f91ed8c..3f522c5 master -> origin/master
Updating f91ed8c..3f522c5
Fast-forward
file1.txt | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
</code></pre>
</p>
</section>
<section>
<h3>Pull behind the scenes</h3>
<p><ul>
<li>So far we've done <b>git pull</b> to get the changes from the remote repository</li>
<li><b>git pull</b> really means <b>git fetch</b> then <b>git merge</b></li>
<li>We'll talk more about merging soon</li>
<li>Be aware that sometimes doing a fetch and then a merge instead of pull can give you more insight into what git is doing</li>
</ul>
</section>
<section>
<h3>Viewing remotes on the command line</h3>
<p><ul>
<li><b>git remote</b> shows and can amend the remote repository</li>
<li>This information is also available in .git/config</li>
<li><b>origin</b> is just git's default name for the remote</li>
<pre><code>
$ git remote -v
origin git@gitlab.example.com:anna/testrepository.git (fetch)
origin git@gitlab.example.com:anna/testrepository.git (push)
</code></pre>
</p>
</section>
<section>
<h3>Basic git rhythm with remote</h3>
<p><ul>
<li>Get updates with <b>git pull</b></li>
<li>Make changes</li>
<li>Stage the changes with <b>git add</b></li>
<li>Commit the changes with <b>git commit</b></li>
<li>Push the changes to the remote with <b>git push</b></li>
</ul></p>
</section>
<section>
<h3>Basic git rhythm with remote</h3>
<p><img width="650" src="img/gitflow.png" alt="gitlab"></p>
</ul></p>
</section>
<section>
<h3>Working collaboratively</h3>
<p><ul>
<li>Git is an amazing tool for working collaboratively</li>
<li>However then we need to start worrying about changes we didn't make</li>
<li>If you're the sole committer to a repository, things are usually straightforwards</li>
<li>However in a team, chances are that people will make conflicting changes at times</li>
<li>Let's take a pragmatic look at two common issues</li>
</ul></p>
</section>
<section>
<h3>Troubleshooting 1: the push is rejected</h3>
<p>
<ul><li>If you try to <b>git push</b> your changes and see something like:</li></ul>
<pre><code>
$ git push
To git@gitlab.example.com:myname/myproject.git
! [rejected] master -> master (fetch first)
error: failed to push some refs to 'git@gitlab.example.com:myname/testrepository.git'
hint: Updates were rejected because the remote contains work that you do not have locally.
</code></pre>
<ul><li>Then you're trying to push before you've updated your local repo with remote changes.</li>
<li>Fix this by doing a <b>git pull</b> first</li>
</ul>
<pre><code>
$ git pull
$ git push
</code></pre>
</p>
</section>
<section>
<h3>Troubleshooting 2: we got a merge conflict</h3>
<p>
<ul>
<li>If we try to <b>git pull</b> (git fetch + git merge) and see something like:</li>
</ul>
<pre><code>
Auto-merging file1.txt
CONFLICT (content): Merge conflict in file1.txt
Automatic merge failed; fix conflicts and then commit the result.
</code></pre>
<ul><li>Then we have a merge conflict we need to resolve</li></ul>
</p>
</section>
<section>
<p>
Let's see what the problem is:
<pre><code>
$ git status
Unmerged paths:
(use "git add <file>..." to mark resolution)
both modified: file1.txt
</code></pre>
<pre><code>
$ git diff
diff --cc file1.txt
index 528038e,f324c51..0000000
--- a/file1.txt
+++ b/file1.txt
@@@ -1,4 -1,4 +1,8 @@@
++<<<<<<< HEAD
+hello
++=======
+ goodbye
++>>>>>>> 3911012567a3a5a0432bea090b82b58d74d5aa9d
</code></pre></p>
</section>
<section>
<p><ul>
<li>Resolution: decide what the file <b>should</b> contain </li>
<li>Git writes markers in the file around conflicting sections</li>
<li>Edit the file (including deleting the markers)</li>
<li>Add, commit, push.</li>
</ul>
<pre><code>
$ cat file1.txt
<<<<<<< HEAD
hello
=======
goodbye
>>>>>>> 3911012567a3a5a0432bea090b82b58d74d5aa9d
$ nano file1.txt
$ git add file1.txt
$ git commit -m "Fixing conflict"
$ git push
</code></pre></p>
</section>
<section>
<h3>Working collaboratively</h3>
<p><ul>
<li>With that in mind, let's move on to using a common repository</li>
<li>For the purposes of this course, we've set up an example repo in Gitlab for us all to clone</li>
<li>Then we can experiment with making and resolving conflicts</li>
</ul></p>
</section>
<section>
<h3>Cloning an existing repository</h3>
<p><ul>
<li>If we want to work on an existing repository, we can either edit the files in Gitlab, or clone the repo locally.</li>
<li>Editing in the UI tends to only be practical for very small, isolated changes.</li>
<li>To clone a repo, find the correct URL in Gitlab, displayed ssh/http on the project page.</li>
<li>SSH needs a key to have been set up, HTTPS needs a username and password.</li>
</ul>
<pre><code data-trim>
$ git clone git@gitlab.example.com:myname/myproject.git
or
$ git clone https://gitlab.example.com/myname/myproject.git
</code></pre></p>
</section>
<section>
<h3>Exercise: Clone a remote</h3>
<p><ul>
<li>Clone the example repo to your local directory</li>
<li>Make a new file, add and commit the changes locally</li>
<li>If you're working in a group, remember to do <b>git pull</b> to get any changes made by other people</li>
<li>Push the changes back to the remote</li>
<li>Did you get any conflicts?</li>
<li>Verify the new file is visible in Gitlab</li>
<pre><code data-trim>
$ git clone git@gitlab.example.com:myname/myproject.git
$ git add ...
$ git commit ...
$ git pull
$ git push
</code></pre>
</p>
</section>
<section>
<h3>Exercise: resolving issues</h3>
<p><ul>
<li>Make a file in the Github UI and commit it</li>
<li><b>Without doing a pull</b>, edit the same file locally</li>
<li>Add and commit the file</li>
<li>What happens when you try to push it back to the remote?</li>
<li>Look at <b>git diff</b> and <b>git status</b></li>
<li>Do a <b>git pull</b> to get the remote changes</li>
<li>This should cause a merge conflict</li>
<li>Edit the file to resolve the conflict</li>
<li>Now try adding, committing, and pushing again</li>
</p>
</section>
<!-- Undoing mistakes -->
<section>
<h1>Undoing mistakes</h1>
</section>
<section>
<h3>Undoing mistakes</h3>
<p><ul>
<li>We're human, and as such we make mistakes</li>
<li>If you use git regularly, you <b>will</b> screw it all up from time to time</li>
<li>Let's look at how to un-screw it up so it's not so terrifying next time</li>
</p>
</section>
<section>
<h3>Git reset to undo local changes</h3>
<p><ul>
<li><b>git reset file1.txt</b> un-stages a file (undoes git add)</li>
<li><b>git reset --soft HEAD~</b> undoes a git commit back to staging</li>
<li><b>git reset --hard HEAD~</b> undoes a git commit entirely</li>
<li>use the commit number to revert to a specific commit</li>
<li>use HEAD~2 to undo the last two commits</li>
</ul></p>
<p><pre><code>
$ git log
commit ecb76ad2f5b753c10f5f24094ea27f29f8c2d004
Second commit
commit 320a8f00a4a0de7c9b3f39851d3bc164d0769697
First commit
$ git reset --hard HEAD~
or
$ git reset --hard 320a8f00a4a0de7c9b3f39851d3bc164d0769697
$ git log
commit 320a8f00a4a0de7c9b3f39851d3bc164d0769697
First commit
</code></pre></p>
</ul></p>
</section>
<section>
<h3>Exercise: Experiment with git reset</h3>
<p><ul>
<li>Create some new files</li>
<li>Add the changes and then use git reset to un-add them</li>
<li>Add and commit some changes then use git reset to undo</li>
<li>How do the --soft and --hard flags change the behaviour?</li>
<li>Can you reset the whole project back to a specific commit?</li>
</ul></p>
<p><pre><code>
$ git reset file2.txt
$ git reset --soft HEAD~
$ git reset --hard HEAD~2
$ git reset --hard 320a8f00a4a0de7c9b3f39851d3bc164d0769697
</code></pre></p>
</section>
<section>
<h3>Git revert</h3>
<p>Undo a commit but retain history
<pre><code>
$ git log
commit 28972f7572e9465cc6a0994ce5fcc31ba2d1afbb
"Adding deploy button"
$ git revert HEAD~
Revert "Adding deploy button"
This reverts commit 28972f7572e9465cc6a0994ce5fcc31ba2d1afbb.
$ git log
commit 78413bb6fec87d10f24ec5c62592795befdb66f7
Reverts "Adding deploy button"
commit 28972f7572e9465cc6a0994ce5fcc31ba2d1afbb
"Adding deploy button"
</code></pre></p>
</section>
<section>
<h3>Exercise: using git revert</h3>
<p><ul>
<li>Make a change in a file</li>
<li>Add, commit, and push it</li>
<li>Now use <b>git revert</b> to roll back that change</li>
<li>Keep an eye on <b>git log</b></li>
<li>What does the history look like when you've finished?</li>
<li>How is this different to <b>git reset</b>?</li>
</ul>
<pre><code>
$ git revert HEAD~
Revert "Adding deploy button"
This reverts commit 28972f7572e9465cc6a0994ce5fcc31ba2d1afbb.
</code></pre></p>
</section>
<!-- Branches -->
<section>
<h1>Branches</h1>
</section>
<section>
<h3>Branches</h3>
<p><ul>
<li>One of git's most powerful features</li>
<li>Allow simultaneous work in different environments</li>
<li>Develop features</li>
<li>Only merge in new code when you're ready</li>
</p>
</section>
<section>
<h3>Git workflow: master branch only</h3>
<p><img width="750" src="img/gitmasteronly.png" alt="git_master_branch"></p>
<p><b>master</b> is git's default main branch</p>
</section>
<section>
<h3>Git workflow: master branch and a hotfix branch</h3>
<p><img width="750" src="img/gitmasterhotfix.png" alt="git_master_branch"></p>
</section>
<section>
<h3>Git workflow: development and release branches</h3>
<p><img width="750" src="img/git.png" alt="git_master_branch"></p>
</section>
<section>
<h3>Branch commands</h3>
<p><ul>
<li><b>git branch</b> displays the checked-out branches</li>
<li><b>git branch <i>branchname</i></b> creates a new branch</li>
<li><b>git checkout <i>branchname</i></b> switches to the new branch</li>
<li><b>git checkout -b</b> combines the above commands to create a new branch and switch to it</li>
</ul>
<pre><code>
$ git branch
* master
$ git branch featurebranch
$ git branch
* master
featurebranch
$ git checkout featurebranch
$ git branch
* featurebranch
master
</code></pre></p>
</section>
<section>
<h3>Exercise: working with branches</h3>
<p>Let's make a new feature branch of the existing repository that you cloned.
<pre><code>
$ git checkout -b featurebranch
Switched to a new branch 'featurebranch'
$ git branch
* featurebranch
master
</code></pre><ul>
<li>Create some more files and edit existing files</li>
<li>Add and commit your changes</li>
<li>The first time you push, you'll need to set up the remote for this branch like:</li>
</p>
<pre><code>
$ git push --set-upstream origin featurebranch
</code></pre><ul>
</p>
</section>
<section>
<h3>Merging branches</h3>
<p><ul>
<li>You've developed a whole new feature in the feature branch, and now it's time to merge it back into the master branch</li>
<li>We can merge branches on the command line</li>
<li>or use <b>merge request</b> in Gitlab (this is called 'pull request' in Github)</li>
<li>Merge requests are more appropriate for merging to production branches as they encourage code review and thoughtful deploys</li>
</p>
</section>
<section>
<h3>Exercise: merging branches in Gitlab</h3>
<p><ul>
<li>In Gitlab, create a new merge request to merge your feature branch into the master branch</li>
<li>Explore the request and check the changes you made</li>
<li>Accept the merge request</li>
<li>See the changes now appear in the main branch in Gitlab</li>
<li>Locally switch back to the master branch with <b>git checkout</b> and do a <b>git pull</b> to get up-to-date</li>
</ul>
<pre><code>
$ git checkout master
Switched to branch 'master'
Your branch is behind 'origin/master' by 2 commits, and can be fast-forwarded.
(use "git pull" to update your local branch)
$ git pull
Updating 7a59581..4d4adb3
Fast-forward
file2.txt | 1 +
1 file changed, 1 insertion(+)
create mode 100644 file2.txt
</code></pre>
</p>
</section>
<section>
<h3>Exercise: merging branches on the command line</h3>
<p><ul>
<li>On the command line, ensure you're on the feature branch</li>