Git Interview Preparation

এই section এ আমরা Git সংক্রান্ত common interview questions এবং তাদের detailed answers দেখব। প্রতিটি topic এ practical examples এবং real-world scenarios রয়েছে।

1. Basic Git Commands Q&A

Q1: `git init` এবং `git clone` এর মধ্যে পার্থক্য কি?

Answer:

git init:

নতুন local repository তৈরি করে
Empty repository initialize করে
Existing project এ Git tracking শুরু করতে ব্যবহার হয়

bash

mkdir my-project
cd my-project
git init
# Creates .git directory

git clone:

Existing remote repository এর copy তৈরি করে
সম্পূর্ণ history সহ repository download করে
Automatically remote connection setup করে

bash

git clone https://github.com/user/repo.git
# Downloads entire repository with history

Key Difference: init নতুন repo তৈরি করে, clone existing repo copy করে।

Q2: `git add` এর বিভিন্ন options explain করুন।

Answer:

bash

# Specific file add করা
git add file.txt

# Multiple files add করা
git add file1.txt file2.txt

# All files in directory add করা
git add .

# All modified and new files add করা
git add -A
# or
git add --all

# Only modified files add করা (new files নয়)
git add -u
# or
git add --update

# Interactive staging
git add -p
# or
git add --patch

# Specific directory add করা
git add src/

Interactive Staging (-p) Example:

bash

git add -p file.txt

# Options:
# y - stage this hunk
# n - don't stage this hunk
# s - split into smaller hunks
# e - manually edit the hunk
# q - quit

Q3: `git commit` এর best practices কি কি?

Answer:

1. Meaningful Commit Messages:

bash

# ❌ Bad
git commit -m "fix"
git commit -m "update"

# ✅ Good
git commit -m "fix(auth): resolve login timeout issue"
git commit -m "feat(api): add user profile endpoint"

2. Atomic Commits:

bash

# প্রতিটি commit একটি logical change represent করবে
git add src/auth/login.js
git commit -m "feat(auth): add login functionality"

git add tests/auth/login.test.js
git commit -m "test(auth): add login tests"

3. Commit Message Structure:

bash

git commit -m "type(scope): subject

body (optional)

footer (optional)"

4. Amending Last Commit:

bash

# Last commit এ file যোগ করা
git add forgotten-file.js
git commit --amend --no-edit

# Commit message edit করা
git commit --amend -m "new message"

Q4: `git status` এবং `git log` এর মধ্যে পার্থক্য কি?

Answer:

git status:

Current state দেখায়
Working directory এবং staging area এর changes দেখায়
Untracked files দেখায়

bash

git status

# Output:
# On branch main
# Changes to be committed:
#   modified: file1.txt
# Changes not staged for commit:
#   modified: file2.txt
# Untracked files:
#   file3.txt

git log:

Commit history দেখায়
Past commits এর record দেখায়
Author, date, message দেখায়

bash

git log

# Useful options:
git log --oneline              # Compact view
git log --graph                # Visual graph
git log --author="John"        # Specific author
git log --since="2 weeks ago"  # Time range
git log -p                     # Show diffs
git log --stat                 # Show statistics

Q5: `git fetch` এবং `git pull` এর পার্থক্য explain করুন।

Answer:

git fetch:

Remote changes download করে কিন্তু merge করে না
Safe operation - local changes affect হয় না
Review করার সুযোগ দেয়

bash

git fetch origin

# Remote changes দেখুন
git log origin/main

# Manual merge করুন
git merge origin/main

git pull:

fetch + merge একসাথে করে
Remote changes download এবং merge করে
Conflicts হতে পারে

bash

git pull origin main

# Equivalent to:
git fetch origin
git merge origin/main

When to Use:

Scenario	Command
Review করে merge করতে চান	`git fetch`
Immediately merge করতে চান	`git pull`
Safe approach চান	`git fetch`
Quick update চান	`git pull`

Q6: `git reset` এর বিভিন্ন modes explain করুন।

Answer:

1. Soft Reset:

bash

git reset --soft HEAD~1

# Effect:
# - Commit undo হয়
# - Changes staging area তে থাকে
# - Working directory unchanged

Use Case: Commit message ভুল হলে বা commits squash করতে।

2. Mixed Reset (Default):

bash

git reset HEAD~1
# or
git reset --mixed HEAD~1

# Effect:
# - Commit undo হয়
# - Changes unstaged হয়
# - Working directory unchanged

Use Case: Commit এবং staging undo করতে, কিন্তু changes রাখতে।

3. Hard Reset:

bash

git reset --hard HEAD~1

# Effect:
# - Commit undo হয়
# - Staging area clear হয়
# - Working directory clean হয়
# - ALL CHANGES LOST!

Use Case: সব changes discard করতে (⚠️ Dangerous!)

Visual Comparison:

Before: A -- B -- C (HEAD)

--soft:   A -- B (HEAD), C's changes in staging
--mixed:  A -- B (HEAD), C's changes unstaged
--hard:   A -- B (HEAD), C's changes deleted

Q7: Untracked files কিভাবে remove করবেন?

Answer:

bash

# Dry run (কি delete হবে দেখুন)
git clean -n

# Untracked files delete করুন
git clean -f

# Untracked directories সহ delete করুন
git clean -fd

# .gitignore এ থাকা files ও delete করুন
git clean -fx

# Interactive mode
git clean -i

Safe Approach:

bash

# 1. প্রথমে dry run করুন
git clean -n

# 2. Confirm করুন কি delete হবে
# 3. তারপর actual clean করুন
git clean -f

2. Rebase vs Merge Questions

Q8: Rebase এবং Merge এর মধ্যে পার্থক্য কি?

Answer:

Merge:

bash

# Feature branch কে main এ merge করা
git checkout main
git merge feature-branch

# Creates a merge commit
# History: A -- B -- C -- M (merge commit)
#               \       /
#                D -- E (feature)

Characteristics:

✅ History preserve করে
✅ Non-destructive
✅ Safe for public branches
❌ Messy history (merge commits)
❌ Graph complex হয়

Rebase:

bash

# Feature branch কে main এর উপর rebase করা
git checkout feature-branch
git rebase main

# Rewrites history
# History: A -- B -- C -- D' -- E' (linear)

Characteristics:

✅ Clean, linear history
✅ Easy to follow
✅ No merge commits
❌ Rewrites history
❌ Dangerous for public branches
❌ Conflicts হতে পারে multiple times

Q9: কখন Merge এবং কখন Rebase ব্যবহার করবেন?

Answer:

Use Merge When:

Public/Shared Branches:

bash

# main, develop branches
git checkout main
git merge feature-branch

Preserving Complete History:

bash

# Important milestones track করতে
git merge --no-ff release/v1.0.0

Team Collaboration:

bash

# অন্যরা যে branch এ কাজ করছে
git merge team-feature

Use Rebase When:

Local Branches:

bash

# শুধু আপনি যে branch এ কাজ করছেন
git rebase main

Cleaning Up Before PR:

bash

# PR submit করার আগে
git rebase -i main

Keeping Feature Branch Updated:

bash

# Feature branch এ main এর latest changes নিতে
git checkout feature-branch
git rebase main

Golden Rule:

Never rebase public branches!

bash

# ❌ NEVER DO THIS
git checkout main
git rebase feature-branch

# ✅ DO THIS INSTEAD
git checkout main
git merge feature-branch

Q10: Interactive Rebase কিভাবে কাজ করে?

Answer:

Basic Interactive Rebase:

bash

# শেষ 5 commits edit করুন
git rebase -i HEAD~5

# Editor opens with:
pick abc1234 feat: add feature A
pick def5678 fix: typo
pick ghi9012 feat: add feature B
pick jkl3456 WIP: temp changes
pick mno7890 fix: bug in feature B

Available Commands:

Command	কাজ
`pick`	Commit রাখুন যেমন আছে
`reword`	Commit message edit করুন
`edit`	Commit এ changes করুন
`squash`	Previous commit এর সাথে merge (message রাখুন)
`fixup`	Previous commit এর সাথে merge (message বাদ)
`drop`	Commit delete করুন
`exec`	Shell command run করুন

Example: Cleaning Up Commits:

bash

# Before:
pick abc1234 feat: add feature A
pick def5678 fix: typo
pick ghi9012 feat: add feature B
pick jkl3456 WIP: temp changes
pick mno7890 fix: bug in feature B

# After editing:
pick abc1234 feat: add feature A
reword def5678 fix: correct typo in feature A
pick ghi9012 feat: add feature B
fixup jkl3456 WIP: temp changes
squash mno7890 fix: bug in feature B

# Result: 3 clean commits instead of 5

Practical Use Cases:

Squashing WIP Commits:

bash

pick abc1234 feat: add login
fixup def5678 WIP
fixup ghi9012 WIP
fixup jkl3456 WIP: almost done
# Result: 1 clean commit

Reordering Commits:

bash

pick abc1234 feat: add feature
pick def5678 docs: update README
pick ghi9012 test: add tests

# Reorder to:
pick abc1234 feat: add feature
pick ghi9012 test: add tests
pick def5678 docs: update README

Splitting a Commit:

bash

edit abc1234 feat: add multiple features

# Git pauses at this commit
git reset HEAD^
git add feature1.js
git commit -m "feat: add feature 1"
git add feature2.js
git commit -m "feat: add feature 2"
git rebase --continue

Q11: Rebase conflicts কিভাবে resolve করবেন?

Answer:

Step-by-Step Process:

bash

# 1. Rebase শুরু করুন
git rebase main

# Conflict হলে:
# CONFLICT (content): Merge conflict in file.txt
# error: could not apply abc1234... commit message

# 2. Conflicted files দেখুন
git status

# 3. Conflicts resolve করুন
# file.txt edit করুন এবং conflict markers remove করুন
<<<<<<< HEAD
main branch এর code
=======
feature branch এর code
>>>>>>> abc1234 (commit message)

# 4. Resolved files stage করুন
git add file.txt

# 5. Rebase continue করুন
git rebase --continue

# যদি আরো conflicts থাকে, repeat steps 3-5

Rebase Abort করা:

bash

# যদি rebase cancel করতে চান
git rebase --abort

# Original state এ ফিরে যাবে

Rebase Skip করা:

bash

# যদি current commit skip করতে চান
git rebase --skip

Tips for Easier Conflict Resolution:

bash

# Rerere enable করুন (Reuse Recorded Resolution)
git config --global rerere.enabled true

# Same conflicts automatically resolve হবে

3. Collaboration Workflow Questions

Q12: Gitflow workflow explain করুন।

Answer:

Branch Structure:

main (production)
  └── develop (integration)
       ├── feature/* (new features)
       ├── release/* (release preparation)
       └── hotfix/* (production fixes)

1. Feature Development:

bash

# Feature branch তৈরি করুন
git checkout develop
git checkout -b feature/user-auth

# Development করুন
git add .
git commit -m "feat(auth): add login"

# Develop এ merge করুন
git checkout develop
git merge --no-ff feature/user-auth
git branch -d feature/user-auth

2. Release Process:

bash

# Release branch তৈরি করুন
git checkout develop
git checkout -b release/v1.0.0

# Version bump এবং bug fixes
git commit -m "chore: bump version to 1.0.0"

# Main এ merge করুন
git checkout main
git merge --no-ff release/v1.0.0
git tag -a v1.0.0 -m "Release 1.0.0"

# Develop এ merge করুন
git checkout develop
git merge --no-ff release/v1.0.0

# Release branch delete করুন
git branch -d release/v1.0.0

3. Hotfix Process:

bash

# Hotfix branch তৈরি করুন
git checkout main
git checkout -b hotfix/critical-bug

# Fix করুন
git commit -m "fix: resolve critical bug"

# Main এ merge করুন
git checkout main
git merge --no-ff hotfix/critical-bug
git tag -a v1.0.1 -m "Hotfix 1.0.1"

# Develop এ merge করুন
git checkout develop
git merge --no-ff hotfix/critical-bug

# Hotfix branch delete করুন
git branch -d hotfix/critical-bug

Advantages:

✅ Clear separation of concerns
✅ Parallel development
✅ Production stability
✅ Easy rollback

Disadvantages:

❌ Complex for small teams
❌ Many long-lived branches
❌ Overhead for simple projects

Q13: Feature Branch Workflow এবং Trunk-Based Development এর পার্থক্য কি?

Answer:

Feature Branch Workflow:

bash

# Long-lived feature branches
main
  ├── feature/user-auth (3 days)
  ├── feature/payment (1 week)
  └── feature/dashboard (2 weeks)

# Workflow:
git checkout -b feature/new-feature
# ... develop for days/weeks ...
git push origin feature/new-feature
# Create PR
# Code review
# Merge to main

Characteristics:

✅ Isolated development
✅ Thorough code review
✅ Feature toggles optional
❌ Integration delays
❌ Merge conflicts
❌ Slower feedback

Trunk-Based Development:

bash

# Short-lived branches (hours/1 day max)
main (trunk)
  ├── feature/quick-fix (2 hours)
  └── feature/small-change (4 hours)

# Workflow:
git checkout -b feature/small-feature
# ... develop for hours ...
git push origin feature/small-feature
# Quick review
# Merge to main immediately

Characteristics:

✅ Continuous integration
✅ Fast feedback
✅ Fewer merge conflicts
✅ Requires feature toggles
❌ Requires discipline
❌ Needs good CI/CD
❌ Incomplete features in main

Comparison:

Aspect	Feature Branch	Trunk-Based
Branch lifetime	Days/weeks	Hours/1 day
Integration frequency	Infrequent	Continuous
Code review	Thorough	Quick
Feature toggles	Optional	Required
CI/CD requirement	Medium	High
Team size	Any	Small to medium

Q14: Pull Request এর best practices কি কি?

Answer:

1. Small, Focused PRs:

bash

# ❌ Bad: Large PR
- 50 files changed
- Multiple features
- Hard to review

# ✅ Good: Small PR
- 5-10 files changed
- One feature/fix
- Easy to review

2. Descriptive Title and Description:

markdown

## ❌ Bad PR Title

"Update files"

## ✅ Good PR Title

"feat(auth): implement JWT authentication"

## ✅ Good PR Description

### Description

Implements JWT-based authentication for API endpoints.

### Changes

- Added JWT token generation
- Implemented middleware for token validation
- Added refresh token mechanism

### Testing

- [x] Unit tests pass
- [x] Integration tests pass
- [x] Manual testing completed

### Related Issues

Closes #123

3. Self-Review Before Submitting:

bash

# PR submit করার আগে:
# 1. Diff review করুন
git diff main...feature-branch

# 2. Tests run করুন
npm test

# 3. Linting check করুন
npm run lint

# 4. Build verify করুন
npm run build

4. Respond to Feedback Promptly:

bash

# Feedback পাওয়ার পরে:
# 1. Changes করুন
git add .
git commit -m "refactor: apply review feedback"

# 2. Push করুন (PR automatically update হবে)
git push origin feature-branch

# 3. Comment করুন কি change করেছেন

5. Keep PR Updated:

bash

# Main branch এর সাথে sync রাখুন
git fetch origin
git rebase origin/main

# অথবা
git merge origin/main

# Force push (if rebased)
git push --force-with-lease origin feature-branch

4. Branching & Merging Scenarios

Q15: Fast-forward merge এবং 3-way merge এর পার্থক্য কি?

Answer:

Fast-Forward Merge:

bash

# Scenario:
main:    A -- B -- C
feature:           D -- E

# Merge:
git checkout main
git merge feature

# Result:
main: A -- B -- C -- D -- E (no merge commit)

Conditions:

Feature branch main থেকে diverge করেনি
Linear history possible
No conflicts

3-Way Merge:

bash

# Scenario:
main:    A -- B -- C -- F
              \
feature:       D -- E

# Merge:
git checkout main
git merge feature

# Result:
main: A -- B -- C -- F -- M
              \         /
feature:       D ----- E
# M = merge commit

Conditions:

Branches diverged
Creates merge commit
Preserves both histories

Forcing Merge Commit:

bash

# Fast-forward possible কিন্তু merge commit চান
git merge --no-ff feature-branch

# Always creates merge commit

Q16: Merge conflict এর একটি practical scenario solve করুন।

Answer:

Scenario:

bash

# main branch:
# file.txt: "Hello World"

# feature-branch:
# file.txt: "Hello Git"

# Merge করলে conflict হবে

Step-by-Step Resolution:

bash

# 1. Feature branch merge করুন
git checkout main
git merge feature-branch

# Output:
# Auto-merging file.txt
# CONFLICT (content): Merge conflict in file.txt
# Automatic merge failed; fix conflicts and then commit the result.

# 2. Conflicted files দেখুন
git status
# On branch main
# You have unmerged paths.
#   (fix conflicts and run "git commit")
#
# Unmerged paths:
#   (use "git add <file>..." to mark resolution)
#         both modified:   file.txt

# 3. file.txt open করুন
<<<<<<< HEAD
Hello World
=======
Hello Git
>>>>>>> feature-branch

# 4. Conflict resolve করুন
# Option A: Keep main version
Hello World

# Option B: Keep feature version
Hello Git

# Option C: Combine both
Hello World and Git

# Option D: Write new version
Hello from Git World

# 5. Conflict markers remove করুন এবং save করুন
Hello from Git World

# 6. File stage করুন
git add file.txt

# 7. Merge commit complete করুন
git commit -m "merge: resolve conflict in file.txt"

# 8. Verify করুন
git log --graph --oneline

Using Merge Tools:

bash

# Visual merge tool ব্যবহার করুন
git mergetool

# Configure merge tool:
git config --global merge.tool vimdiff
# or
git config --global merge.tool meld
# or
git config --global merge.tool kdiff3

Q17: Detached HEAD state কি এবং কিভাবে recover করবেন?

Answer:

Detached HEAD কি:

bash

# Specific commit checkout করলে
git checkout abc1234

# Output:
# You are in 'detached HEAD' state.
# HEAD is now at abc1234

# Visualization:
main: A -- B -- C -- D (main)
                 ↑
              HEAD (detached at C)

Why It Happens:

Specific commit checkout করলে
Tag checkout করলে
Remote branch directly checkout করলে

Recovery Options:

Option 1: Create New Branch:

bash

# Detached HEAD state এ
git branch new-branch-name
git checkout new-branch-name

# অথবা একসাথে:
git checkout -b new-branch-name

Option 2: Return to Branch:

bash

# Simply checkout a branch
git checkout main

# Changes হারিয়ে যাবে (যদি commit না করে থাকেন)

Option 3: Save Changes:

bash

# যদি detached HEAD এ changes করে থাকেন
git commit -m "changes in detached HEAD"

# Commit hash note করুন
# abc1234

# Branch এ ফিরে যান
git checkout main

# Changes merge করুন
git merge abc1234

Preventing Data Loss:

bash

# Detached HEAD এ থাকলে সবসময় branch তৈরি করুন
git checkout -b temp-branch

# তারপর কাজ করুন

5. Debugging with Git

Q18: `git reflog` কি এবং কিভাবে ব্যবহার করবেন?

Answer:

Git Reflog কি:

reflog হলো Git এর "safety net" - এটি HEAD এর সব movements track করে, এমনকি deleted commits ও।

Basic Usage:

bash

# Reflog দেখুন
git reflog

# Output:
abc1234 HEAD@{0}: commit: add feature
def5678 HEAD@{1}: checkout: moving from main to feature
ghi9012 HEAD@{2}: reset: moving to HEAD~1
jkl3456 HEAD@{3}: commit: deleted commit

Common Use Cases:

1. Recovering Deleted Commits:

bash

# Accidentally hard reset করেছেন
git reset --hard HEAD~3

# Commits lost! কিন্তু reflog এ আছে
git reflog

# Output:
abc1234 HEAD@{0}: reset: moving to HEAD~3
def5678 HEAD@{1}: commit: important work
ghi9012 HEAD@{2}: commit: more work
jkl3456 HEAD@{3}: commit: even more work

# Recover করুন
git reset --hard HEAD@{1}
# অথবা
git reset --hard def5678

2. Recovering Deleted Branch:

bash

# Branch delete করেছেন
git branch -D feature-branch

# Reflog দেখুন
git reflog

# Output:
abc1234 HEAD@{0}: checkout: moving from feature-branch to main
def5678 HEAD@{1}: commit: last commit on feature-branch

# Branch recreate করুন
git checkout -b feature-branch def5678

3. Finding Lost Stash:

bash

# Stash drop করে ফেলেছেন
git stash drop

# Reflog দেখুন
git reflog

# Output:
abc1234 HEAD@{0}: WIP on main: stashed changes

# Stash recover করুন
git stash apply abc1234

4. Undoing Rebase:

bash

# Rebase করেছেন কিন্তু undo করতে চান
git reflog

# Output:
abc1234 HEAD@{0}: rebase finished
def5678 HEAD@{1}: checkout: moving from main to feature

# Rebase আগের state এ ফিরে যান
git reset --hard HEAD@{1}

Reflog Expiry:

bash

# Reflog entries 90 days পর expire হয়
# Configure করুন:
git config --global gc.reflogExpire 180.days
git config --global gc.reflogExpireUnreachable 90.days

Q19: `git bisect` দিয়ে bug কিভাবে খুঁজবেন?

Answer:

Git Bisect কি:

Binary search ব্যবহার করে bug introduce করা commit খুঁজে বের করে।

Basic Workflow:

bash

# 1. Bisect শুরু করুন
git bisect start

# 2. Current commit কে bad mark করুন
git bisect bad

# 3. Known good commit mark করুন
git bisect good abc1234

# Git automatically middle commit checkout করবে
# Bisecting: 5 revisions left to test after this

# 4. Test করুন
# যদি bug আছে:
git bisect bad

# যদি bug নেই:
git bisect good

# 5. Repeat করুন যতক্ষণ না bug commit পাওয়া যায়

# Output:
# abc1234 is the first bad commit
# commit abc1234
# Author: John Doe
# Date: Mon Jan 1 12:00:00 2024
#     feat: add new feature (this introduced the bug)

# 6. Bisect শেষ করুন
git bisect reset

Automated Bisect:

bash

# Test script তৈরি করুন (test.sh)
#!/bin/bash
npm test
exit $?

# Automated bisect run করুন
git bisect start
git bisect bad
git bisect good abc1234
git bisect run ./test.sh

# Git automatically bug commit খুঁজে বের করবে

Practical Example:

bash

# Scenario: Login feature broken, was working 10 commits ago

# 1. Start bisect
git bisect start

# 2. Current state is bad
git bisect bad

# 3. 10 commits ago was good
git log --oneline -10
# abc1234 (10 commits ago)
git bisect good abc1234

# 4. Git checks out middle commit (5 commits ago)
# Test manually: npm start, try login

# 5. Login works!
git bisect good

# 6. Git checks out commit between 5 and 10 (7-8 commits ago)
# Test: Login broken!
git bisect bad

# 7. Continue until found:
# def5678 is the first bad commit
# commit def5678
# feat(auth): refactor login logic

# 8. Reset
git bisect reset

# 9. Fix the bug in def5678
git show def5678

Bisect with Skip:

bash

# যদি কোনো commit test করা যায় না (build fails)
git bisect skip

# Git পরের commit check করবে

Visualizing Bisect:

bash

# Bisect চলাকালীন log দেখুন
git bisect log

# Bisect visualization
git bisect visualize
# অথবা
git bisect view

Q20: Lost commits কিভাবে recover করবেন?

Answer:

Method 1: Using Reflog (Easiest):

bash

# Reflog check করুন
git reflog

# Output:
abc1234 HEAD@{0}: reset: moving to HEAD~5
def5678 HEAD@{5}: commit: lost commit

# Recover করুন
git cherry-pick def5678
# অথবা
git reset --hard def5678

Method 2: Using fsck (Reflog expired হলে):

bash

# Dangling commits খুঁজুন
git fsck --lost-found

# Output:
# dangling commit abc1234
# dangling commit def5678
# dangling blob ghi9012

# Commits inspect করুন
git show abc1234
git show def5678

# Recover করুন
git cherry-pick abc1234
# অথবা
git merge abc1234

Method 3: Recovering from Deleted Branch:

bash

# Branch delete করার পরে
git branch -D feature-branch

# Reflog দেখুন
git reflog

# Output:
abc1234 HEAD@{1}: commit: last commit on feature-branch

# Branch recreate করুন
git checkout -b feature-branch abc1234

Method 4: Recovering Stashed Changes:

bash

# Stash list দেখুন
git stash list

# যদি stash drop করে থাকেন
git fsck --unreachable | grep commit

# Stash commits খুঁজুন
git show abc1234

# Apply করুন
git stash apply abc1234

Prevention Tips:

bash

# 1. Regular backups
git push origin --all

# 2. Use branches instead of detached HEAD
git checkout -b temp-branch

# 3. Don't use --hard reset unless sure
git reset --soft HEAD~1  # Safer

# 4. Enable rerere
git config --global rerere.enabled true

6. Additional Git Topics Q&A

Q21: Git internals - Objects, Blobs, Trees, Commits explain করুন।

Answer:

Git Object Model:

Commit
  ├── Tree (directory structure)
  │    ├── Blob (file content)
  │    ├── Blob (file content)
  │    └── Tree (subdirectory)
  │         └── Blob (file content)
  └── Parent commit(s)

1. Blob (Binary Large Object):

bash

# File content store করে
# File name নেই, শুধু content

# Example:
echo "Hello World" | git hash-object --stdin
# Output: 557db03de997c86a4a028e1ebd3a1ceb225be238

# Blob দেখুন
git cat-file -p 557db03
# Output: Hello World

2. Tree:

bash

# Directory structure store করে
# File names এবং permissions রাখে

# Tree দেখুন
git cat-file -p main^{tree}

# Output:
# 100644 blob 557db03... file1.txt
# 100644 blob 8ab686e... file2.txt
# 040000 tree 9c3f7a2... src/

3. Commit:

bash

# Metadata store করে
# - Tree reference
# - Parent commit(s)
# - Author, committer
# - Commit message

# Commit দেখুন
git cat-file -p HEAD

# Output:
# tree 9c3f7a2...
# parent abc1234...
# author John Doe <john@example.com> 1234567890 +0000
# committer John Doe <john@example.com> 1234567890 +0000
#
# feat: add new feature

4. Tag:

bash

# Commit এ reference
# Annotated tags additional metadata রাখে

# Tag দেখুন
git cat-file -p v1.0.0

# Output:
# object abc1234...
# type commit
# tag v1.0.0
# tagger John Doe <john@example.com>
#
# Release version 1.0.0

Object Storage:

bash

# Objects .git/objects/ এ store হয়
ls .git/objects/

# Object hash এর first 2 characters = directory
# Remaining characters = filename

# Example:
# 557db03de997c86a4a028e1ebd3a1ceb225be238
# Stored at: .git/objects/55/7db03de997c86a4a028e1ebd3a1ceb225be238

Q22: `git stash` এর advanced usage explain করুন।

Answer:

Basic Stashing:

bash

# Current changes stash করুন
git stash

# অথবা message সহ
git stash save "WIP: working on feature"

# Stash list দেখুন
git stash list
# Output:
# stash@{0}: WIP on main: abc1234 commit message
# stash@{1}: WIP on feature: def5678 another commit

Advanced Stash Operations:

1. Partial Stashing:

bash

# Interactive stashing
git stash -p

# Options:
# y - stash this hunk
# n - don't stash
# s - split into smaller hunks
# e - manually edit

2. Stash Untracked Files:

bash

# Untracked files সহ stash করুন
git stash -u
# অথবা
git stash --include-untracked

# Ignored files সহও stash করুন
git stash -a
# অথবা
git stash --all

3. Stash Specific Files:

bash

# শুধু specific files stash করুন
git stash push -m "stash specific files" file1.txt file2.txt

# Path pattern ব্যবহার করুন
git stash push -m "stash all JS files" "*.js"

4. Apply vs Pop:

bash

# Apply করুন (stash রাখুন)
git stash apply

# Specific stash apply করুন
git stash apply stash@{1}

# Pop করুন (stash remove করুন)
git stash pop

# Specific stash pop করুন
git stash pop stash@{1}

5. Stash Branch:

bash

# Stash থেকে নতুন branch তৈরি করুন
git stash branch new-branch-name

# অথবা specific stash থেকে
git stash branch new-branch stash@{1}

6. Stash Show:

bash

# Stash changes দেখুন
git stash show

# Detailed diff দেখুন
git stash show -p

# Specific stash দেখুন
git stash show stash@{1} -p

7. Stash Drop and Clear:

bash

# Specific stash delete করুন
git stash drop stash@{1}

# All stashes clear করুন
git stash clear

Practical Scenarios:

bash

# Scenario 1: Quick context switch
git stash
git checkout hotfix-branch
# ... fix bug ...
git checkout main
git stash pop

# Scenario 2: Try experimental changes
git stash
# ... experiment ...
git stash  # Stash experiments
git stash pop stash@{1}  # Restore original work

# Scenario 3: Clean working directory for pull
git stash
git pull
git stash pop

Q23: `git cherry-pick` কিভাবে কাজ করে?

Answer:

Cherry-Pick কি:

Specific commit(s) অন্য branch এ apply করা।

Basic Usage:

bash

# Single commit cherry-pick করুন
git cherry-pick abc1234

# Multiple commits cherry-pick করুন
git cherry-pick abc1234 def5678 ghi9012

# Commit range cherry-pick করুন
git cherry-pick abc1234..def5678

Practical Scenarios:

Scenario 1: Hotfix to Multiple Branches:

bash

# main এ hotfix করেছেন
git checkout main
git commit -m "fix: critical bug"  # abc1234

# develop এ same fix চান
git checkout develop
git cherry-pick abc1234

# release branch এও চান
git checkout release/v1.0
git cherry-pick abc1234

Scenario 2: Selective Feature Migration:

bash

# feature-branch এ multiple commits
# শুধু specific commits main এ চান

git log feature-branch --oneline
# abc1234 feat: add login
# def5678 feat: add signup
# ghi9012 WIP: incomplete feature
# jkl3456 feat: add logout

# শুধু login এবং logout চান
git checkout main
git cherry-pick abc1234 jkl3456

Cherry-Pick Options:

bash

# Commit করবেন না, শুধু apply করুন
git cherry-pick -n abc1234
# অথবা
git cherry-pick --no-commit abc1234

# Edit commit message
git cherry-pick -e abc1234
# অথবা
git cherry-pick --edit abc1234

# Sign-off যোগ করুন
git cherry-pick -s abc1234
# অথবা
git cherry-pick --signoff abc1234

Handling Conflicts:

bash

# Cherry-pick করলে conflict হলে
git cherry-pick abc1234

# CONFLICT (content): Merge conflict in file.txt

# Conflicts resolve করুন
# ... edit file.txt ...

git add file.txt
git cherry-pick --continue

# অথবা abort করুন
git cherry-pick --abort

Cherry-Pick vs Merge:

Aspect	Cherry-Pick	Merge
Scope	Specific commits	Entire branch
History	Creates new commits	Preserves history
Use case	Selective changes	Complete integration
Conflicts	Per commit	Once

Q24: Git Hooks এর practical examples দিন।

Answer:

Git Hooks Location:

bash

# Hooks .git/hooks/ directory তে থাকে
ls .git/hooks/

# Sample hooks:
# pre-commit.sample
# commit-msg.sample
# pre-push.sample

1. Pre-Commit Hook (Linting):

bash

# .git/hooks/pre-commit
#!/bin/sh

echo "Running linter..."
npm run lint

if [ $? -ne 0 ]; then
  echo "❌ Linting failed! Fix errors before committing."
  exit 1
fi

echo "✅ Linting passed!"

2. Commit-Msg Hook (Message Validation):

bash

# .git/hooks/commit-msg
#!/bin/sh

commit_msg=$(cat "$1")

# Check for conventional commit format
if ! echo "$commit_msg" | grep -qE "^(feat|fix|docs|style|refactor|test|chore)(\(.+\))?: .+"; then
  echo "❌ Invalid commit message format!"
  echo "Use: type(scope): subject"
  echo "Example: feat(auth): add login"
  exit 1
fi

echo "✅ Commit message valid!"

3. Pre-Push Hook (Testing):

bash

# .git/hooks/pre-push
#!/bin/sh

echo "Running tests..."
npm test

if [ $? -ne 0 ]; then
  echo "❌ Tests failed! Fix tests before pushing."
  exit 1
fi

echo "✅ Tests passed!"

4. Post-Commit Hook (Notification):

bash

# .git/hooks/post-commit
#!/bin/sh

# Get commit info
commit_hash=$(git rev-parse HEAD)
commit_msg=$(git log -1 --pretty=%B)
author=$(git log -1 --pretty=%an)

# Send notification (example)
echo "New commit by $author: $commit_msg" >> commit-log.txt

5. Pre-Rebase Hook (Protection):

bash

# .git/hooks/pre-rebase
#!/bin/sh

# Prevent rebasing main branch
if [ "$2" = "main" ]; then
  echo "❌ Cannot rebase main branch!"
  exit 1
fi

Making Hooks Executable:

bash

chmod +x .git/hooks/pre-commit
chmod +x .git/hooks/commit-msg
chmod +x .git/hooks/pre-push

Sharing Hooks with Team (using Husky):

bash

# Install Husky
npm install --save-dev husky
npx husky install

# Add hooks
npx husky add .husky/pre-commit "npm run lint"
npx husky add .husky/commit-msg "npx commitlint --edit $1"
npx husky add .husky/pre-push "npm test"

# Hooks এখন version control এ আছে
# Team members automatically পাবে

Q25: Git Submodules কি এবং কখন ব্যবহার করবেন?

Answer:

Submodules কি:

অন্য Git repository কে আপনার repository এর মধ্যে include করা।

Adding Submodule:

bash

# Submodule add করুন
git submodule add https://github.com/user/library.git libs/library

# .gitmodules file তৈরি হবে
cat .gitmodules
# [submodule "libs/library"]
#     path = libs/library
#     url = https://github.com/user/library.git

# Commit করুন
git add .gitmodules libs/library
git commit -m "chore: add library submodule"

Cloning Repository with Submodules:

bash

# Repository clone করুন
git clone https://github.com/user/main-repo.git

# Submodules initialize এবং update করুন
git submodule init
git submodule update

# অথবা একসাথে:
git clone --recurse-submodules https://github.com/user/main-repo.git

Updating Submodules:

bash

# Submodule directory তে যান
cd libs/library

# Latest changes pull করুন
git pull origin main

# Parent repository তে ফিরে যান
cd ../..

# Submodule update commit করুন
git add libs/library
git commit -m "chore: update library submodule"

Removing Submodule:

bash

# 1. Deinitialize submodule
git submodule deinit libs/library

# 2. Remove from .git/modules
rm -rf .git/modules/libs/library

# 3. Remove from working tree
git rm libs/library

# 4. Commit
git commit -m "chore: remove library submodule"

When to Use Submodules:

✅ Use Cases:

Shared libraries across projects
Third-party dependencies
Monorepo alternative
Versioned dependencies

❌ Avoid When:

Simple dependencies (use package manager)
Frequently changing code
Team unfamiliar with submodules
Need automatic updates

Alternatives:

bash

# Git Subtree (simpler alternative)
git subtree add --prefix libs/library https://github.com/user/library.git main

# Package managers (npm, pip, etc.)
npm install library

Q26: Large files Git এ কিভাবে handle করবেন?

Answer:

Problem:

bash

# Large files commit করলে:
# - Repository size বড় হয়
# - Clone slow হয়
# - History bloated হয়

Solution 1: Git LFS (Large File Storage):

bash

# Install Git LFS
git lfs install

# Track large files
git lfs track "*.psd"
git lfs track "*.mp4"
git lfs track "*.zip"

# .gitattributes file তৈরি হবে
cat .gitattributes
# *.psd filter=lfs diff=lfs merge=lfs -text
# *.mp4 filter=lfs diff=lfs merge=lfs -text

# Commit করুন
git add .gitattributes
git commit -m "chore: configure Git LFS"

# Large files add করুন
git add large-file.psd
git commit -m "feat: add design file"
git push

Solution 2: .gitignore:

bash

# Large files ignore করুন
echo "*.psd" >> .gitignore
echo "*.mp4" >> .gitignore
echo "node_modules/" >> .gitignore

# Alternative storage ব্যবহার করুন
# - Cloud storage (S3, Google Drive)
# - CDN
# - Artifact repository

Solution 3: BFG Repo-Cleaner (Already committed large files):

bash

# Install BFG
# Download from: https://rtyley.github.io/bfg-repo-cleaner/

# Remove large files from history
java -jar bfg.jar --strip-blobs-bigger-than 100M my-repo.git

# Clean up
cd my-repo
git reflog expire --expire=now --all
git gc --prune=now --aggressive

# Force push
git push --force

Best Practices:

bash

# 1. Check file sizes before committing
git ls-files -s | awk '{print $4, $2}' | sort -n

# 2. Use .gitignore proactively
# 3. Use Git LFS for binary files
# 4. Keep repository lean
# 5. Regular cleanup

Summary

এই interview preparation guide এ আমরা cover করেছি:

✅ Basic Commands - init, clone, add, commit, status, log, fetch, pull, reset
✅ Rebase vs Merge - Differences, use cases, interactive rebase, conflict resolution
✅ Collaboration Workflows - Gitflow, feature branch, trunk-based, PR best practices
✅ Branching & Merging - Fast-forward, 3-way merge, conflict scenarios, detached HEAD
✅ Debugging - reflog, bisect, recovering lost commits
✅ Additional Topics - Internals, stash, cherry-pick, hooks, submodules, large files

এই Q&A গুলো practice করলে আপনি Git interview এ confident থাকতে পারবেন! 🚀

Tips for Interview Success

Hands-on Practice: শুধু theory পড়বেন না, commands practice করুন
Understand Concepts: Commands মুখস্থ না করে concepts বুঝুন
Real-world Examples: নিজের projects এ apply করুন
Explain Clearly: Technical terms সহজভাবে explain করতে পারুন
Ask Questions: Interviewer কে clarifying questions জিজ্ঞাসা করুন

Good Luck! 🎯

Git Interview Preparation ​

1. Basic Git Commands Q&A ​

Q1: git init এবং git clone এর মধ্যে পার্থক্য কি? ​

Q2: git add এর বিভিন্ন options explain করুন। ​

Q3: git commit এর best practices কি কি? ​

Q4: git status এবং git log এর মধ্যে পার্থক্য কি? ​

Q5: git fetch এবং git pull এর পার্থক্য explain করুন। ​

Q6: git reset এর বিভিন্ন modes explain করুন। ​

Q7: Untracked files কিভাবে remove করবেন? ​

2. Rebase vs Merge Questions ​

Q8: Rebase এবং Merge এর মধ্যে পার্থক্য কি? ​

Q9: কখন Merge এবং কখন Rebase ব্যবহার করবেন? ​

Q10: Interactive Rebase কিভাবে কাজ করে? ​

Q11: Rebase conflicts কিভাবে resolve করবেন? ​

3. Collaboration Workflow Questions ​

Q12: Gitflow workflow explain করুন। ​

Q13: Feature Branch Workflow এবং Trunk-Based Development এর পার্থক্য কি? ​

Q14: Pull Request এর best practices কি কি? ​

4. Branching & Merging Scenarios ​

Q15: Fast-forward merge এবং 3-way merge এর পার্থক্য কি? ​

Q16: Merge conflict এর একটি practical scenario solve করুন। ​

Q17: Detached HEAD state কি এবং কিভাবে recover করবেন? ​

5. Debugging with Git ​

Q18: git reflog কি এবং কিভাবে ব্যবহার করবেন? ​

Q19: git bisect দিয়ে bug কিভাবে খুঁজবেন? ​

Q20: Lost commits কিভাবে recover করবেন? ​

6. Additional Git Topics Q&A ​

Q21: Git internals - Objects, Blobs, Trees, Commits explain করুন। ​

Q22: git stash এর advanced usage explain করুন। ​

Q23: git cherry-pick কিভাবে কাজ করে? ​

Q24: Git Hooks এর practical examples দিন। ​

Q25: Git Submodules কি এবং কখন ব্যবহার করবেন? ​

Q26: Large files Git এ কিভাবে handle করবেন? ​

Summary ​

Tips for Interview Success ​

Git Interview Preparation

1. Basic Git Commands Q&A

Q1: `git init` এবং `git clone` এর মধ্যে পার্থক্য কি?

Q2: `git add` এর বিভিন্ন options explain করুন।

Q3: `git commit` এর best practices কি কি?

Q4: `git status` এবং `git log` এর মধ্যে পার্থক্য কি?

Q5: `git fetch` এবং `git pull` এর পার্থক্য explain করুন।

Q6: `git reset` এর বিভিন্ন modes explain করুন।

Q7: Untracked files কিভাবে remove করবেন?

2. Rebase vs Merge Questions

Q8: Rebase এবং Merge এর মধ্যে পার্থক্য কি?

Q9: কখন Merge এবং কখন Rebase ব্যবহার করবেন?

Q10: Interactive Rebase কিভাবে কাজ করে?

Q11: Rebase conflicts কিভাবে resolve করবেন?

3. Collaboration Workflow Questions

Q12: Gitflow workflow explain করুন।

Q13: Feature Branch Workflow এবং Trunk-Based Development এর পার্থক্য কি?

Q14: Pull Request এর best practices কি কি?

4. Branching & Merging Scenarios

Q15: Fast-forward merge এবং 3-way merge এর পার্থক্য কি?

Q16: Merge conflict এর একটি practical scenario solve করুন।

Q17: Detached HEAD state কি এবং কিভাবে recover করবেন?

5. Debugging with Git

Q18: `git reflog` কি এবং কিভাবে ব্যবহার করবেন?

Q19: `git bisect` দিয়ে bug কিভাবে খুঁজবেন?

Q20: Lost commits কিভাবে recover করবেন?

6. Additional Git Topics Q&A

Q21: Git internals - Objects, Blobs, Trees, Commits explain করুন।

Q22: `git stash` এর advanced usage explain করুন।

Q23: `git cherry-pick` কিভাবে কাজ করে?

Q24: Git Hooks এর practical examples দিন।

Q25: Git Submodules কি এবং কখন ব্যবহার করবেন?

Q26: Large files Git এ কিভাবে handle করবেন?

Summary

Tips for Interview Success