How to edit a file on GitHub and revert a pull request

Alex Tutor

Wednesday of week four. Support has forwarded the same customer note three times: the delivery page says couriers call "30 minutes before arival".

You

In module one I needed Daniel to explain what a commit even was. Today I'd like to fix this with my own hands.

Daniel

Please do. It's text on a page, and page texts belong to you and Emma. I'll review it like any other pull request.

Alex Tutor

Before the clicks, the boundary. A PM can safely edit copy and docs: page texts in .md files, the FAQ, the README, issue templates. And it all still goes through a pull request.

Daniel

Code and config stay with engineers: .tsx files, config/prices.json, anything in .github/workflows/. One missing comma in a config file can stop the whole site from building.

You

Even though a price in config/prices.json is just a number?

Daniel

Even then. The code reads that number at checkout. Ask for the change, and I make it with tests and Oscar's review, like the threshold in #133.

Alex Tutor

Question 1

Which of these changes can Sofia make without an engineer, in the browser and through a pull request? Select all that apply.

Choose all that applyFix a typo in pages/delivery.mdChange freeDeliveryFrom in config/prices.jsonUpdate an answer in pages/faq/delivery.mdTweak the button logic in components/CheckoutButton.tsxAdd a hint to the bug report template in .github/ISSUE_TEMPLATE/Edit the deploy job in .github/workflows/

Alex Tutor

Start on the repository page, Code tab. Open the pages folder, then delivery.md. Or press t and type "delivery" to search by file name.

You

Found it. Line 15: "Couriers call 30 minutes before arival." And the branch selector above the file says main.

Alex Tutor

At the top right of the file there's a pencil icon, Edit this file as of 2026. It opens GitHub's web editor, right in the browser.

Daniel

Nothing is saved while you type, and nothing can break. Until you commit, the editor is only a draft in your browser tab.

Alex Tutor

Fix the word, then open the Preview tab to see the text as it will look on the page, not as raw Markdown.

Alex Tutor

The edit in `pages/delivery.md`

 Couriers deliver within one day in Kyiv.
-Couriers call 30 minutes before arival.
+Couriers call 30 minutes before arrival.

One word changed, so Git shows the whole line twice: the old version removed, the new one added.

Alex Tutor

Question 2

Pressing the pencil icon on a file in main creates a new branch straight away, and every keystroke is saved to it.

TrueFalse

Alex Tutor

Now the green Commit changes… button. A dialog opens with a commit message, an optional extended description, and a choice of where the commit goes.

You

The message box already says "Update delivery.md".

Daniel

GitHub's default. True, and useless in a history of two thousand commits. Say what changed: "Fix typo in courier note".

Alex Tutor

Then the choice. "Commit directly to the main branch" isn't open to you: branch protection lets changes into main only through pull requests. So pick "Create a new branch for this commit and start a pull request".

Daniel

GitHub suggests a name like catchow-sofia-patch-1. It works, but rename it to our habit: content/delivery-typo.

You

Then Propose changes. The commit lands on the new branch, and main hasn't changed at all.

Alex Tutor

Question 3

Why does Sofia's commit go to a new branch instead of straight into main?

Choose one answerThe web editor can never commit to main, in any repositorymain is protected: changes reach it only through a pull request, after review and checksTypo fixes must wait for the Thursday releaseSofia's account isn't allowed to create commits

Alex Tutor

Propose changes leads to "Open a pull request": base main, compare content/delivery-typo. The title comes from the commit message; the description is yours to write.

You

What: fixes "arival" on the delivery page. Why: support forwarded it three times. How to test: open the preview and read the courier note. Reviewer: Daniel.

Alex Tutor

Then Create pull request. It's #168, and the checks start at once: build, test, and preview with its own link.

Daniel

By the way, you can't approve your own pull request. GitHub doesn't let authors approve, so our "one approving review" always means someone else looked.

Alex Tutor

While the checks run, Emma spots the pull request and asks for one more line under the courier note: "Earn loyalty points on every order and spend them at checkout."

You

Same file, same branch. I open delivery.md on content/delivery-typo, add her line and commit straight to that branch: "Mention loyalty points on delivery page".

Daniel

New title, "Fix courier typo and mention loyalty points". Checks green, the preview reads well. Approved.

Alex Tutor

You press Squash and merge: one commit on main, the branch deleted, and the deploy finishes four minutes later.

Alex Tutor

Pull request #168, Wednesday 11:20

Fix courier typo and mention loyalty points#168
Squash-merged into main by Sofia · branch content/delivery-typo deleted
Daniel
Approved
build
test
preview
deploy (production)
Finished four minutes after the merge

Alex Tutor

Question 4

Put the steps of a change made in the browser in order, from opening the file to the live page.

Tap an item, then tap where it should go. You can also drag or use the arrows.

You

Support again. A customer read the new line and asks where to find her points. She can't find them: loyalty points are still switched off for customers.

Alex Tutor

Emma's programme page sits behind the loyalty-points flag; Daniel built that check into #157. A sentence in pages/delivery.md has no flag around it. Merged and deployed means shown.

Daniel

Same mistake as my menu link before v1.4.1: the feature was hidden, one way into it wasn't. And I missed it in review too.

You

So we're announcing loyalty points six days before the launch. How do I take it back?

Alex Tutor

Question 5

Why do customers see the loyalty line on the delivery page, even though the flag loyalty-points is off?

Choose one answerA flag switches itself on when a page mentions its featureSquash merging switches all flags onThe deploy skips flag checks for text filesThe sentence is plain page text with no flag check around it, so once merged and deployed, everyone sees it

Alex Tutor

Open #168. At the bottom of Conversation, next to the note that it was merged, there's a Revert button, as of 2026.

A revert deletes nothing. GitHub makes a new branch, revert-168-content/delivery-typo, with one commit that does the exact opposite of #168, and prepares a pull request for it.

Daniel

That's #169, and it follows the same rules as any pull request: checks and one approval. Undoing a change is still a change. I'm on it.

You

Approved, checks green, squash-merged, deployed. The loyalty line is gone. And so is my typo fix: "arival" is back.

Alex Tutor

Because #168 became one squash commit holding both changes, and a revert undoes the whole commit. History keeps everything: your commit, the revert, and who did what.

Alex Tutor

The change and its revert on mainNothing disappears: the revert is a new commit that undoes f3c8d21. Both stay in the history, and #168 still shows Merged.

c3f7a05Show points balance in the account (#166)v1.5.0
8d2b6e9Write loyalty programme page (#157)
5e9a1b4Fix typo in courier note
1a7c4f2Mention loyalty points on delivery pagecontent/delivery-typo
f3c8d21Fix courier typo and mention loyalty points (#168)
a6b0e53Revert "Fix courier typo and mention loyalty points"revert-168-content/delivery-typo
d7e2f48Revert "Fix courier typo and mention loyalty points" (#169)main

Alex Tutor

Question 6

Every commit on this main has been deployed. Which changes are live on the site now?

main of another shop, newest at the bottom

a1Update shipping FAQ
a2Add spring sale banner
a3Change footer phone number
a4Revert "Add spring sale banner"main

Choose one answerAll three changes, because a revert never removes anythingOnly the shipping FAQ update: a revert also undoes everything after the reverted commitThe shipping FAQ update and the new footer phone number; the banner is gone, though its commit a2 is still in the historyNone of them: a revert resets main to its first commit

You

Couldn't I just have deleted the loyalty line in a new pull request?

Alex Tutor

You could: that's fixing forward, a new change that corrects the problem. It would have kept your typo fix. Both are fine; the question is which gets the site right fastest and most safely.

Daniel

Revert when the live site is wrong and you want the last known good version back now, especially when the right fix isn't obvious yet. Fix forward when the fix is tiny and clear, or when a revert would take good changes with it.

Alex Tutor

And the button doesn't always work. If later changes touched the same lines, GitHub can't build the revert on its own, and an engineer does it by hand.

Daniel

Also, reverting code doesn't undo what already happened. If a bug gave customers wrong points, a revert stops new ones, but fixing their balances needs a plan, not a button.

You

Here the line was a promise we can't keep yet, and the typo is harmless for another hour. Reverting first was fine.

Alex Tutor

Question 7

Match each situation after a merge with the better way to undo it.

Tap an answer, then tap the row it belongs to. You can also drag.

A merged banner shows the wrong sale dates, and the right dates are still being confirmed
A merged FAQ answer has one wrong number, and the right one is known
The last merge broke checkout for everyone, and the cause is unclear
A big pull request with five good changes has one small copy mistake

Answers left to place

You

Then #170: branch content/courier-typo, one commit "Fix typo in courier note", the same title. Only the typo.

Daniel

Approved. And the loyalty line gets its own pull request, ready to merge on 10 November, the morning the flag goes on for everyone.

Alex Tutor

One more thing: Emma should hear why her line disappeared. She asked for it in good faith, and she'll want it back in six days.

You

Two or three sentences in the team chat, then.

Alex Tutor

Question 8Short answer · AI-checked task

Write Emma a 2–3 sentence chat message: why her loyalty line was removed from the delivery page, what is live now, and when and how the line comes back. The launch (flag on for all customers) is on 10 November.

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Alex Tutor

If you'd like to rehearse, make a personal practice repository, or take GitHub Skills' free "Introduction to GitHub" course. Nothing you click there can reach a real site.

You

Tonight, then. Breaking things where nobody sees them sounds relaxing.

Daniel

Everyone learns by breaking something. The trick is to break it in a pull request, where it's easy to undo.

Alex Tutor

Then the last task of the course: plan a change the way you would on Monday, from the first click to the undo plan.

Alex Tutor

Question 9Case · AI-checked task

Plan the change for issue #175 from start to finish.

Support opened issue #175 "Returns FAQ still says 14 days". Finance confirmed in the issue: from Monday customers can return unopened food within 30 days instead of 14.

pages/faq/returns.md, line 8: "You can return unopened food within 14 days."
config/returns.json: "returnWindowDays": 14. The checkout reads this value to accept or refuse returns in the customer's account.

main is protected (pull requests only, 1 approval, checks build and test); every merge is deployed within minutes; the team squash-merges; branch names follow content/… and fix/….

Write your plan: what you edit yourself and what you hand over; the steps in the browser; the branch name and commit message; the pull request title and description, including how it links to #175; who reviews and what you check before and after the merge; and your undo plan if something goes wrong.

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Alex Tutor

Tuesday, 10 November, 9:00. The flag loyalty-points goes on for all customers, and a minute later Emma's line is back on the delivery page, in its own pull request. You close #147 as completed.

You

In module one I was afraid one wrong click could break the whole shop. Now I know what a click can and can't do, and how to take it back.

Daniel

And now you have your own revert story. Welcome to the team's history.

Alex Tutor

That's the course: history and diffs, branches and merges, pull requests and reviews, states, workflows and releases, issues and boards, and a change of your own. The repository is no longer a black box. It's the team's shared memory, and you can write in it.

Alex Tutor

That’s the lesson. You answered every task — nicely done.

Back to the course