Git for Testing vs. Production

1Branch equals your own copy. Main equals everyone's.

Nothing new happens technically in this session; sessions 04 and 05 already gave you everything needed. What changes is how to think about it. On this repository, a branch is not just a scratch space for a risky edit. It is a complete, private copy of the whole site, exactly as every other branch has been since session 04: same files, same pages, same CSS, isolated until you merge it. Main is the one branch connected to the pipeline from session 02, which means main is also the only branch anyone outside the people actively editing it will ever see rendered as the real, Entra-gated site.

That gives you, for free, the thing every engineering team pays good money to build: a safe copy to test changes in and a separate, protected copy that staff actually depend on.

2What a branch looks like before it reaches main

Cloudflare Pages, the service session 02 named as the thing that rebuilds this site, is commonly set up to build a preview of a branch or a pull request at its own separate, unlisted address, before that branch ever touches main. That preview is a real, working copy of the site built from your branch's files, reachable for review without affecting what staff see. Whether preview builds are turned on for this specific project is a Cloudflare Pages setting, not a git one, so check with whoever administers the Cloudflare project if you want to confirm it before relying on it.

Either way, the git side of this is unaffected: you branch, you commit, you push the branch, and whatever Cloudflare does with that branch, main is not touched until you merge.

3Why main is never the place to try something

Session 04 already made the technical case: a push to main is the one event that rebuilds the live site behind Entra. Here is the practical version. Trying a change directly on main means the very first time you see whether it actually works is also the first time every signed-in staff member sees it, or sees it broken. A branch removes that coincidence entirely. You can get something wrong, several times, entirely on your own branch, and nobody else ever has to know it happened.

4The flow in full

The sequence holds whether or not a preview build is configured. Without one, "review" simply means reading the diff and, if the practice folder is handy, trying the change there before merging. The discipline, not the tooling, is what keeps main safe.

5A short pre-merge checklist

Before running git merge or accepting a pull request into main on a site people are actually using, four quick checks cover most real mistakes:

6Try it: see what's actually out there

Read-only, on the real HN - Training repository.

1. Run git branch -a. The -a flag lists remote branches too, not only the one you are on. See whether any branch other than main currently exists on this repository.
2. Run git log main -3 --oneline. This is what a reviewer would read first: the most recent handful of commits already on main, for context before looking at anything new.
3. If you have access to the repository on github.com, open the Pull requests tab and note whether Cloudflare Pages has posted a preview link on any past one. That is the concrete answer to whether preview builds are active on this project.

7Check for understanding

1. Why does trying an untested change directly on main carry more risk here than on a typical personal project?

   A.Because main does not support branches on this repository. B.Because a push to main triggers a rebuild of the live, Entra-gated site that every signed-in staff member can reach. C.Because commits to main cannot be undone, unlike commits on any other branch. D.Because main has a stricter file size limit than other branches.
   Answer

   The risk is specific to this project's pipeline: a push to main is what triggers Cloudflare Pages to rebuild the live site, which Entra then shows to every signed-in staff member. An untested change pushed straight there reaches that whole audience as soon as the build completes, which is exactly what a branch avoids.

   Show the answer
2. What determines whether a Cloudflare Pages preview build exists for a given branch?

   A.Git creates one automatically for every branch that is pushed. B.A setting on the Cloudflare Pages project, independent of git itself. C.Whether the branch name contains the word preview. D.Entra ID, which decides whether a branch is allowed to be previewed.
   Answer

   Whether a branch gets its own preview build is configured on the Cloudflare Pages project, a setting independent of git. Git's job is the same either way: branch, commit, push. What Cloudflare does with that push is a separate layer, worth confirming with whoever administers the project.

   Show the answer
3. In the pre-merge checklist, what is git diff main...your-branch actually for?

   A.It merges the branch into main immediately if no conflicts are found. B.It shows every change the branch would bring, so you can read it before trusting it onto main. C.It deletes any files on main that the branch does not have. D.It checks the branch for broken links automatically.
   Answer

   git diff is read-only. Comparing main against your branch before merging shows exactly what is about to change, which is what lets you, or a reviewer on a pull request, decide whether it is actually ready rather than trusting it blind.

   Show the answer
4. What is the one thing that stays true in the flow diagram in section 4, whether or not a preview build is configured?

   A.Review is skipped entirely if no preview build exists. B.Production only rebuilds after the branch is merged into main. C.A branch cannot be created unless a preview build is already configured. D.Merge conflicts only occur on branches that have a preview build.
   Answer

   The one fixed point in the flow is the last step: production, the live Entra-gated site, only rebuilds once a merge actually lands on main. Everything before that, including whether a preview build exists, is about making the decision to merge a well-informed one; it does not change when production itself updates.

   Show the answer

8Before session 07

• Note what you found when you ran git branch -a in the lab. Session 07 asks who should be able to see those branches at all.

9Glossary

Production

The live, published version of the site, built from main and shown to staff behind Entra.

Preview build

A separate, working build of a branch or pull request at its own address, used to review a change before it reaches production.

Pre-merge review

Reading the diff, and ideally seeing the change run, before merging a branch into main.

10Sources

• Cloudflare, Preview deployments, Cloudflare Pages documentation.
• GitHub, GitHub flow, for the branch-review-merge-deploy sequence this session applies to this project.