Chapter 3: Branch, Merge, Rebase, Stash and Pull Requests

3.15 Lab — colour, one conflict, one stash

By Ravindra Bagale · Last updated: 25 October 2026

Why: the problem

This lab joins the whole chapter into one story on one practice repo. You will use branches, a real conflict, a merge commit, the history graph, stash, an annotated tag, and a decision on rebase, exactly like a normal week on a team. Do it without looking at the notes first; look only when you are stuck. Save your terminal outputs in a notes file, because the graph and the tag output are what a reviewer or interviewer will ask you to explain. Before the lab steps, warm up with the examples below, which rebuild the practice repo and give you checks to prove each step is done.

What we will build

You will build a fresh practice repo with badge.py, then run the lab steps: branch, conflict, merge, graph, stash, tag and the rebase decision. Checks at the end prove each step.

What: every term in plain English

• Practice repo — A repo you are allowed to break.
• badge.py — The starter file with BADGE_COLOR.
• Conflict — Same line changed on both sides.
• Merge commit — Two parents; joins the branches.
• Stash — Parking for unfinished edits.
• Annotated tag — Release name with message.
• Rebase decision — Rebase only if the branch is not shared.
• Evidence — Saved outputs in notes.txt.

How: step by step

1. Create repo

   mkdir -p ~/devops-lab/ch3-lab && cd ~/devops-lab/ch3-lab && git init -q -b main
   

   What it does: Fresh.

   Output

   (no output)
   

2. Identity check

   git config user.name && git config user.email
   

   What it does: Commits need these.

   Output

   Ravi Learner
   ravi@example.com
   

3. Starter file

   echo 'BADGE_COLOR = "green"' > badge.py && git add . && git commit -qm "Add badge starter"
   

   What it does: The base.

   Output

   (no output)
   

4. Notes file

   echo "# ch3 lab notes" > ~/devops-lab/ch3-notes.txt
   

   What it does: Outside the repo.

   Output

   (no output)
   

5. Ignore notes

   git status -s
   

   What it does: Notes are not in the repo.

   Output

   (no output)
   

6. Ready

   git log --oneline
   

   What it does: One commit.

   Output

   7a7a7a7 Add badge starter
   

7. Save evidence helper

   echo 'save(){ "$@" | tee -a ~/devops-lab/ch3-notes.txt; }' >> ~/.bashrc && . ~/.bashrc
   

   What it does: Run save CMD to log output.

   Output

   (no output)
   

Example 1: Warm-up: the conflict in one script

Stack. Git

Goal. Warm-up: the conflict in one script.

warmup.sh

cd ~/devops-lab/ch3-lab
git switch -qc feature/badge-colour
sed -i 's/green/gold/' badge.py && git commit -qam "Gold badge"
git switch -q main
sed -i 's/green/blue/' badge.py && git commit -qam "Set campaign colour to blue"
git merge feature/badge-colour || true
git diff --name-only --diff-filter=U

What each line does

• Two sides — Same line, gold and blue.
• || true — The script goes on after the expected failure.
• diff-filter=U — Lists the conflicted file.

Green output

CONFLICT (content): Merge conflict in badge.py
Automatic merge failed; fix conflicts and then commit the result.
badge.py

Expected result. The conflict from lab step 3 is ready to read.

Example 2: Resolve, graph, and save evidence

Stack. Git

Goal. Resolve, graph, and save evidence.

resolve.sh

printf 'BADGE_COLOR = "gold"\n' > badge.py
grep -c -E "^(=======|>>>>>>>)" badge.py || echo "0 markers"
git add badge.py && git commit -q --no-edit
save git log --oneline --graph --decorate -8

What each line does

• Keep gold — As the lab asks.
• Marker check — Must be 0.
• save — Graph goes into notes.

Green output

0 markers
*   8b8b8b8 (HEAD -> main) Merge branch 'feature/badge-colour'
|\
| * 9c9c9c9 (feature/badge-colour) Gold badge
* | 0d0d0d0 Set campaign colour to blue
|/
* 7a7a7a7 Add badge starter

Expected result. Steps 4 and 5 done, with proof saved.

Example 3: Stash round-trip and tag

Stack. Git

Goal. Stash round-trip and tag.

stash-tag.sh

git switch -qc feature/badge-size
echo 'BADGE_SIZE = 32' >> badge.py
git stash push -m "wip"
git switch -q main && git status -s
git switch -q feature/badge-size && git stash pop -q && tail -1 badge.py
git switch -q main
git tag -a v1.2.0 -m "Release 1.2.0: gold badge" 8b8b8b8
save git show v1.2.0 --no-patch

What each line does

• stash push — Park the size edit.
• pop — Bring it back on the branch.
• tag -a on the merge — Release marker.

Green output

BADGE_SIZE = 32
tag v1.2.0
Tagger: Ravi Learner <ravi@example.com>
Release 1.2.0: gold badge
commit 8b8b8b8...
Merge: 0d0d0d0 9c9c9c9

Expected result. Steps 6 and 7 done. The tag shows the merge commit with two parents.

Example 4: Final checks and the rebase answer

Stack. Git

Goal. Final checks and the rebase answer.

checks.sh

git log --merges --oneline | wc -l
git cat-file -t v1.2.0
git stash list | wc -l
git branch --merged main
echo "Rebase feature/badge-size on main only while it is mine and unpushed; refuse once a teammate has pulled it." >> ~/devops-lab/ch3-notes.txt
wc -l ~/devops-lab/ch3-notes.txt

What each line does

• 1 merge — Conflict merge exists.
• tag — Annotated.
• 0 stashes — Popped.
• --merged — feature/badge-colour can be deleted.
• Rebase sentence — Step 8.

Green output

1
tag
0
  feature/badge-colour
* main
19 /home/ravi/devops-lab/ch3-notes.txt

Expected result. Every lab step has proof in your notes file.

Verify: did it work?

1. Merge exists

   git -C ~/devops-lab/ch3-lab log --merges --oneline | wc -l
   

   What it does: One.

   Output

   1
   

2. Tag

   git -C ~/devops-lab/ch3-lab tag -l
   

   What it does: Release.

   Output

   v1.2.0
   

3. Value

   cat ~/devops-lab/ch3-lab/badge.py | head -1
   

   What it does: Gold.

   Output

   BADGE_COLOR = "gold"
   

When it is red 1

CONFLICT (content): Merge conflict in badge.py

Cause. Expected in step 3.

Fix, step by step

1. Read, keep gold, remove markers, add, commit.

When it is red 2

error: Your local changes would be overwritten by checkout

Cause. You switched without stashing in step 6.

Fix, step by step

1. git stash push -m "wip" first.

When it is red 3

fatal: tag 'v1.2.0' already exists

Cause. You ran step 7 twice.

Fix, step by step

1. git tag -l; nothing more to do.

When it is red 4

save: command not found

Cause. The helper is not loaded.

Fix, step by step

1. . ~/.bashrc

Cleanup

1. Remove lab

   rm -rf ~/devops-lab/ch3-lab
   

   What it does: Keep the notes file.

   Output

   (no output)
   

Practice tasks

Homework: try at home

Recap

• One story uses the whole chapter.
• Conflict: read, choose, remove markers.
• Graph proves the merge.
• Stash, then tag the release.
• Save evidence for review.

FAQ

Can I use VS Code for the conflict?

Yes, but still check for markers before commit.

Do I need a remote?

No. Step 9 is optional.

What if I keep blue?

Then the lab answer differs; the lab asks for gold.

Why tag the merge commit?

It is the released state.

Can I repeat the lab?

Yes. Remove the folder and start again.

Interview questions

1. Walk me through resolving a conflict.

   Merge, list files, read markers, choose final lines, remove markers, test, add, commit.

2. How do you show history shape?

   git log --oneline --graph --decorate.

3. When do you stash?

   To switch tasks with uncommitted work.

4. Why annotated tags for releases?

   They record who, when and why.

5. Rebase or merge for a shared branch?

   Merge.

Samajla ka?

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