Step 12 — Two branches, two of everything¶

About 25 minutes. Branch: step-12.

The one new idea: a branch is a whole separate app.

The thing step 0 asked you to take on trust¶

You have deployed one branch for eleven steps because this page's fact was stated up front without being shown. Now you see it.

Make a second branch:

git checkout -b experiment
git push -u origin experiment
mecca app redeploy tally -b experiment

Wait for it, then:

mecca app show tally -b tutorial
mecca app show tally -b experiment

Two different URLs. And behind them:

	`tutorial`	`experiment`
URL	its own	its own
Database	its own	its own — and empty
Redis	its own keyspace	its own
Environment variables	its own	its own
Deploy history, queue rows, logs	its own	its own

Open the experiment branch's board. The seed items are there — because 001_items.sql ran against a fresh database and seeded it — and any idea you submitted on tutorial is not. Nothing is shared. It is a different application that happens to be built from a neighbouring commit.

Tell them apart¶

mecca var set tally TALLY_LABEL="experiment" -b experiment
mecca app redeploy tally -b experiment

A badge appears on that one and not the other.

This is the step where mecca var set without -b bites

Without -b, it writes to every branch of the app. Run the command above without it and both boards get the badge — including the one you think of as live.

mecca var list tally -b <branch> shows you what a given branch actually has, and is worth checking after any var set you were not fully awake for.

Which one is real?¶

Once there are two, something has to say:

mecca app set-production tally -b tutorial

That is what the dashboard reads to decide which branch is the app, and what mecca falls back to when a command needs a branch and was not given one.

A branch called main is treated slightly differently

It is the branch that gets no segment in the URL. So the same app deployed from main and from tutorial differ in the shape of their hostname, not just its content — worth knowing before it surprises you.

Clean up¶

mecca app delete tally -b experiment

Deleting one branch does not touch the other. They were separate all along — which is the point of the whole step, demonstrated one last way.

If it didn't work¶

Symptom	Try	Usually
Both branches show one URL	`mecca app show -b <each>`	The second deploy has not finished
The badge is on both	`mecca var list -b <each>`	`var set` without `-b`
The second branch has no data	—	Correct. Its database is its own, and new

Reset to the reference¶

git checkout tutorial
git fetch upstream && git reset --hard upstream/step-12 && git push --force origin tutorial

Next: Step 13 — Backups