PB173
Perl
Table of Contents
Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  1
Create a project. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  1
Local repository . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  1
Updating materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  2
Corrections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  2
Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
Tips and tricks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
Setup
This document explains how to use PB173 Perl Git repository and how to submit homeworks.
Create a project
1. Navigate to https://gitlab.fi.muni.cz/xlacko1/pb173-perl and fork the repository.
Make sure you set Visibility to Private.
2. This next step is extremely important, do not skip it!
Remove the fork relationship:
Settings → General → Advanced → Remove fork relationship.
The rest of this manual should still apply, except the step 3 below.
3. Give access right to your tutor.
Settings → Project information → Members.
Here, invite your tutor (xlacko1) with role Reporter.
 Create a SSH key and add it to your account in GitLab to make authentication easier.
Local repository
Clone your repository on the computer you wish to use when working on tutorials or homework
assignments. This can be Aisa, your own personal computer, someone else’s personal computer you
hacked into, …
1. Clone the repository.
In the project dashboard, copy the URL (SSH if you have set up your SSH keys, HTTPS otherwise)
and clone it on your computer, for example:
$ git clone git@gitlab.fi.muni.cz:‹LOGIN›/pb173-perl
$ cd pb173-perl
2. Set up upstream repository.
From now on, we will call your repository “origin”, and the official repository belonging to the
tutor shall be known as the “upstream”.
Create a new remote in your repository called upstream to point to the official repository. Use
either SSH or HTTPS link:
# HTTPS
$ git remote add upstream https://gitlab.fi.muni.cz/xlacko1/pb173-perl
# SSH
$ git remote add upstream git@gitlab.fi.muni.cz:xlacko1/pb173-perl.git
PB173 Perl 1 / 5
Updating materials
Initially, branch main contains a single (empty) initial commit. This branch is for you to do as you
please, and where you are advised to work on your tutorials. You can create other branches if you
wish.
Before every tutorial, new materials will be pushed into the seminar branch of the upstream
repository. All you need to do is merge them into your main branch.
Make sure you start in your main branch:
$ git status
Now update the materials:
$ git fetch upstream seminar
$ git merge upstream/seminar
$ git push
When you are finished with the tutorials, you are advised to commit and push what you have done to
your origin repository.
Corrections
If an error is found in tests or source materials, the correction will usually appear in the seminar branch,
and the above commands will be enough to fix it.
However, if an error is found in a homework after you are expected to have modified it (and you did),
you will be advised to update with some named commits using cherry-picking.
 If you have not yet started with the affected homework, just update your materials!
# MAKE SURE YOUR REPOSITORY IS CLEAN
# TIP: See ‹git stash› below
# Update main branch as above
$ git switch main
$ git fetch upstream seminar
$ git merge upstream/seminar
$ git push
# Get back to your homework
$ git switch HOMEWORK-BRANCH
$ git cherry-pick COMMITS… # COMMITS… will be specified in the forum
If this results in conflicts, either you can try to fix them manually or reach out to your tutor.
PB173 Perl 2 / 5
Homework
Each seminar will contain a few homework assignments, or tasks. You can choose any subset of these
tasks to work on; even empty.
Since this seminar is quite small, we will not use any additional tools, GitLab will be enough. The
solution will therefore be submitted as Merge request (MR from now on).
If you decide to solve more than one task, you have to submit each of them in a separate MR.
1. Start from a clean repository.
Use git status to confirm you are in your main branch with no changed files.
2. Create a branch for your homework.
The name of the branch must have the homework code including the last letter, for example hw03b.
Then push your new branch to GitLab:
$ git switch --create hw03b
$ git push --set-upstream origin hw03b
If git switch is not available (usually on older systems), use git checkout -b hw03b instead.

Old Git on Aisa
Aisa’s distribution is old and does not understand git switch. There, you have the following
options:
1. Use git checkout [-b] BRANCH instead of git switch [-c] BRANCH.
2. Use Git from modules, module add git-2.25.1
3. Work on your homework.
In the homework branch you should only modify files regarding the task. Create commits
regularly, especially when you want to switch to a different branch. Don’t forget to use git push
and git pull as well if you want to access your work from different computers.
4. Create a MR and submit your homework for review.
When finished, make sure you made git push. Then create a MR:
Project’s left panel → Merge requests → New merge request
◦ In Source branch, select the branch with your homework.
◦ Make sure that Target branch names your project’s main branch.
◦ Click Compare branches and continue.
PB173 Perl 3 / 5
In the main MR form, fill in a few details:
◦ The Title must begin with Draft: CODE where CODE is the homework code, e.g. hw03b. You can add
: and your own title after this.
◦ Add xlacko1 to Reviewers field.
◦ (Optionally) set Assignee to yourself.
◦ (Optionally) check Delete source branch when merge request is accepted option.
You can set other options (like Description or Labels) as you please.
Finally, click Create merge request.
5. Now you wait.
Do not Merge your homework immediately. This is where the Draft: part in the title comes in
handy, as GitLab will prevent you from clicking Merge as long as this prefix remains there.
6. Review.
You will likely recieve review for your solution in GitLab as well. In rare cases the review might be
delivered by an e-mail or an owl.
If your solution is good enough and clean, your Merge Request will be approved. Otherwise you
are expected to work on the task a bit more. Read the review carefully.
There is no need to create MR for the resubmit, simply switch back to your homework branch,
make changes as necessary, and then commit and push them. GitLab will automatically update the
MR.

Avoid squashing commits or using git push --force for review. While these techniques are
useful in production environments, they can make homework reviews and updates quite
messy.
7. Acceptance.
Once your homework is accepted, you will receive a mark in IS for each accepted task. Whether
you merge this branch into your main repository is up to you.
Tips and tricks
1. Use git status before each commit and push.
This will help you to avoid messing up branches or creating merge conflicts.
2. Do not leave uncommited work.
Always create commits for something you have done or finished, especially if you wish to switch
branches.
PB173 Perl 4 / 5
3. Stash.
If you want to switch branch, or do something that requires a clean repository, but you have
unfinished work that is not worthy of a commit yet, look at the git stash command (man git
stash).
Short version:
$ git stash
Take uncommited changes and store them in a stage area (you can imagine it as a virtual commit)
without making changes to your current branch. You will end up with a clean repository.
$ git stash list
List stashes, useful when you have more than one.
$ git stash pop [stash]
When you want to resume working on the stash, use this command to restore changes on top of
your current branch. You may wish to specify the stash if you have more than one.
 You can use git stash before git merge or git pull to temporarily clean out the repository.
4. Graph.
While there are some external tools to visualise commits and branches of your repository, Git can
do that too:
$ git log --oneline --decorate --graph --all
You can create a handy alias for this command, like
$ git config [--global] alias.graph 'log --oneline --decorate --grah --all'
$ git graph
 Do not be afraid to ask for help
If you get stuck with Git or you think you messed up, do not panic. Git is a very powerful
versioning system, and while it tries to protect you from trouble, it is not perfect. Things like
these do sometimes happen.
Do not hesitate to ask for help in IS MU Discussions or on Discord.
PB173 Perl 5 / 5