Resolving Merge Conflicts 🌿

# A conflict happens when two branches change the SAME lines of the SAME
# file, so Git can't decide which version is correct. It refuses to guess
# and hands the decision to you.
#
#   main   had:  color: blue;
#   you    made: color: red;     (on branch main)
#   teammate made: color: green; (on branch feature-branch)
#                                 -> both touch line 5 -> CONFLICT
#
# What does NOT conflict (Git merges these for you, no markers):
#   - different files were modified
#   - the same file, but different lines
#   - one branch adds new content, the other leaves that area alone
#
# Try to merge a branch that changed the same line and Git stops:
git merge feature-branch

Auto-merging style.css
CONFLICT (content): Merge conflict in style.css
Automatic merge failed; fix conflicts and then commit the result.

# When a conflict happens, Git edits the file IN PLACE and inserts three
# markers around the clashing section. Open style.css and you'll see:

body {
  font-size: 16px;
<<<<<<< HEAD
  color: red;          # YOUR version  (the branch you are ON, called HEAD)
=======
  color: green;        # THEIR version (the branch you are merging IN)
>>>>>>> feature-branch
  margin: 0;
}

# Read the markers like this:
#   <<<<<<< HEAD        start of YOUR version (everything above =======)
#   =======             the dividing line between the two versions
#   >>>>>>> feature-branch   end of THEIR version (everything below =======)
#
# Note: "font-size" and "margin" are OUTSIDE the markers — Git merged those
# fine. Only the lines Git couldn't reconcile are wrapped.

# To resolve, you EDIT the file by hand: pick the version you want (or
# combine them, or write something new), then DELETE all three markers.
# Here you decide "green" is correct, so the finished file reads:

body {
  font-size: 16px;
  color: green;        # kept THEIR version; HEAD line + all 3 markers gone
  margin: 0;
}

# A conflict is "resolved" when NO markers remain. Git doesn't care which
# side you keep — it only checks that <<<<<<<, =======, and >>>>>>> are gone.

# 🎯 YOUR TURN — a conflict in greeting.txt. You decide the page should
# say "Welcome back!" (THEIR version). Write the file with NO markers left.

# The conflicted file currently looks like this:
#   <<<<<<< HEAD
#   Hello!
#   =======
#   Welcome back!
#   >>>>>>> feature-greeting

# Replace ___ with the single correct resolved line:
___                       # 👉 the one line that should remain (no markers!)

# ✅ Expected resolved greeting.txt:
#   Welcome back!

# The full resolve-a-conflict routine, start to finish.

# 1. A merge triggers a conflict
git merge feature-auth

# 2. See exactly which files are conflicted ("both modified")
git status

# 3. Open each file, choose/combine the changes, and remove every
#    <<<<<<<, =======, and >>>>>>> marker. (VS Code shows clickable
#    "Accept Current / Incoming / Both Changes" buttons above the markers.)
code src/App.js

# 4. Stage the resolved file — this is how you tell Git "I fixed it"
git add src/App.js
#    For several conflicted files: resolve each, then  git add .

# 5. Finish the merge with a commit (Git pre-fills a merge message)
git commit -m "Merge feature-auth"

Auto-merging src/App.js
CONFLICT (content): Merge conflict in src/App.js
Automatic merge failed; fix conflicts and then commit the result.

On branch main
You have unmerged paths.
  (fix conflicts and run "git commit")

Unmerged paths:
  (use "git add <file>..." to mark resolution)
        both modified:   src/App.js

[main abc1234] Merge feature-auth

# 🎯 YOUR TURN — you've already edited config.json and deleted every
# conflict marker. Two commands are left to FINISH the merge.

# 1) Tell Git the conflict in config.json is resolved
___ config.json          # 👉 the command that stages a resolved file

# 2) Complete the merge by recording a commit
git ___ -m "Merge feature-config"   # 👉 the verb that records a commit

# ✅ Expected: git status afterwards shows "working tree clean"
#    and the merge appears in  git log --oneline

# Made a mess, or merged the wrong branch? Don't panic and don't start
# deleting markers blindly. One command rewinds you to BEFORE the merge,
# as if it never happened — no commits, no half-resolved files:
git merge --abort

# After aborting, your working tree is clean again:
git status

On branch main
nothing to commit, working tree clean

# The best conflict is one that never happens. Prevention strategies:
#   - Merge/pull often so your branch never drifts far from main.
#   - Keep branches small and focused (fewer changes = fewer clashes).
#   - Communicate so two people don't rewrite the same file at once.
#   - Don't mix a big refactor and a new feature in one branch/PR.
#   - Use .gitignore so generated files never cause fake conflicts.

# A simple "stay in sync" routine — pull main into your feature branch:
git checkout main
git pull origin main
git checkout my-feature
git merge main

# Create a .gitignore so build artefacts are never tracked (and so they
# never collide on merge):
cat > .gitignore <<'EOF'
node_modules/
dist/
.env
.DS_Store
*.log
coverage/
EOF
git add .gitignore
git commit -m "Add .gitignore"

Already up to date.
Updating a1b2c3d..e4f5g6h
Fast-forward
 README.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

[my-feature 7h8i9j0] Add .gitignore
 1 file changed, 6 insertions(+)
 create mode 100644 .gitignore