468 lines
9.4 KiB
Markdown
468 lines
9.4 KiB
Markdown
# Git Commands Guide for DevOps Engineers
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**Professional Reference Document**
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*Comprehensive Git workflow for development, CI/CD pipelines, and team collaboration*
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---
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## Table of Contents
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1. [Installation and Setup](#1-installation-and-setup)
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2. [SSH Key Configuration](#2-ssh-key-configuration)
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3. [Repository Initialization](#3-repository-initialization)
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4. [Basic Workflow](#4-basic-workflow)
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5. [Status and History](#5-status-and-history)
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6. [File Operations](#6-file-operations)
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7. [Branch Management](#7-branch-management)
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8. [Merging and Rebasing](#8-merging-and-rebasing)
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9. [Remote Operations](#9-remote-operations)
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10. [Commit Management](#10-commit-management)
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11. [Removing Commits](#11-removing-commits)
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12. [Stash Operations](#12-stash-operations)
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13. [Tags and Releases](#13-tags-and-releases)
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14. [.gitignore Management](#14-gitignore-management)
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15. [Configuration and Aliases](#15-configuration-and-aliases)
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16. [Troubleshooting and Recovery](#16-troubleshooting-and-recovery)
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17. [Repository Cloning](#17-repository-cloning)
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---
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## 1. Installation and Setup
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### **Install Git**
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Download from official source: [git-scm.com](https://git-scm.com/)
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**Linux Distributions:**
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```bash
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# Debian/Ubuntu
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sudo apt update && sudo apt install git -y
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# RHEL/CentOS/Fedora
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sudo yum install git -y # or dnf install git -y
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```
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**macOS:**
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```bash
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brew install git
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```
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### **Verify Installation**
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```bash
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git --version
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```
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*Displays installed Git version*
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### **Configure User Identity**
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Git requires author information for every commit:
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```bash
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git config --global user.name "Your Full Name"
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git config --global user.email "your.email@company.com"
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```
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**Configuration Scopes:**
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| Scope | Command Flag | Applies To | Persistence |
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|-------|--------------|------------|-------------|
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| System | `--system` | All users on machine | System-wide |
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| Global | `--global` | Current user | User account |
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| Local | `--local` | Specific repository | Repository only |
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**Verify Configuration:**
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```bash
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git config --list
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```
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---
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## 2. SSH Key Configuration
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### **Generate SSH Key Pair**
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```bash
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ssh-keygen -t ed25519 -C "your.email@company.com"
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```
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- **`-t ed25519`**: Modern, secure key algorithm
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- **`-C`**: Comment for key identification
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### **SSH Agent Management**
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```bash
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# Start SSH agent
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eval "$(ssh-agent -s)"
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# Add private key to agent
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ssh-add ~/.ssh/id_ed25519
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```
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### **Per-Repository SSH Key**
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```bash
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# Set custom key for specific repo
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git config --local core.sshCommand "ssh -i /path/to/custom_key"
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# Clone with specific key (one-time)
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git -c core.sshCommand="ssh -i /path/to/key" clone git@host:repo.git
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```
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---
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## 3. Repository Initialization
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### **Create New Repository**
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```bash
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# Initialize with main branch
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git init -b main
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# Initialize with default branch
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git init
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```
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**Key Concepts:**
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- **Working Directory**: Files not yet tracked by Git
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- **Staging Area (Index)**: Files prepared for commit
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- **Repository**: Committed history and metadata
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---
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## 4. Basic Workflow
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### **Stage Changes**
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```bash
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# Stage all changes (new, modified, deleted)
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git add -A
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# Stage specific files
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git add <file1> <file2>
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# Stage all modified files (not new files)
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git add .
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```
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### **Commit Changes**
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```bash
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git commit -m "Descriptive commit message"
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```
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### **Connect to Remote**
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```bash
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git remote add origin <repository-url>
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git remote -v # Verify remote configuration
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```
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### **Push to Remote**
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```bash
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# First push (sets upstream tracking)
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git push -u origin main
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# Subsequent pushes
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git push
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```
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---
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## 5. Status and History
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### **Repository Status**
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```bash
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git status
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```
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*Shows working directory and staging area state*
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### **Commit History**
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```bash
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# One-line summary
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git log --oneline
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# Visual graph of all branches
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git log --graph --oneline --all
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# Last N commits with patch
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git log -p -3
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# Show specific commit details
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git show <commit-hash>
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```
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### **Change Visualization**
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```bash
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# Unstaged changes (working directory)
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git diff
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# Staged changes (index vs HEAD)
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git diff --staged
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# Branch comparison
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git diff main..develop
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```
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---
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## 6. File Operations
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| Operation | Command | Effect |
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|-----------|---------|---------|
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| Stage file | `git add <file>` | Moves file to staging area |
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| Unstage | `git reset <file>` | Removes from staging, keeps changes |
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| Discard changes | `git restore <file>` | Reverts to last committed version |
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| Rename | `git mv old new` | Stages rename operation |
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| Remove (tracked) | `git rm <file>` | Stages file deletion |
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| Untrack | `git rm --cached <file>` | Removes from Git, keeps locally |
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---
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## 7. Branch Management
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### **Branch Operations**
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```bash
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# Create and switch
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git switch -c feature/new-api
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# List branches
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git branch -v # Local branches with last commit
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git branch -a # All branches (local + remote)
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# Delete branch
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git branch -d feature # Safe delete (merged)
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git branch -D feature # Force delete
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# Rename branch
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git branch -m old-name new-name
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```
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**Branch States:**
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- **Local Branch**: Exists only in your repository
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- **Remote Branch**: Exists on remote server (`origin/main`)
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- **Tracking Branch**: Local branch linked to remote (`main -> origin/main`)
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---
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## 8. Merging and Rebasing
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### **Merge (Preserves History)**
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```bash
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git checkout main
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git merge feature/xyz
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```
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**Merge Types:**
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| Type | Condition | Result |
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|------|-----------|---------|
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| Fast-forward | Target ahead, no divergence | Linear history |
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| Three-way | Both branches have new commits | Merge commit created |
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### **Rebase (Linear History)**
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```bash
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git checkout feature/xyz
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git rebase main
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```
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**Rebase Controls:**
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```bash
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git rebase --abort # Cancel rebase
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git rebase --continue # Resolve conflicts and continue
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```
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---
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## 9. Remote Operations
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### **Remote Management**
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```bash
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git remote -v # List remotes
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git remote show origin # Detailed remote info
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git fetch --all # Fetch all remotes
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```
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### **Pull Strategies**
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```bash
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git pull # Fetch + merge
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git pull --rebase # Fetch + rebase (cleaner history)
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```
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---
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## 10. Commit Management
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### **Modify Last Commit**
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```bash
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git commit --amend # Edit message/files
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```
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### **Safe Undo (Shared Branches)**
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```bash
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git revert <commit-hash> # Creates reversing commit
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```
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### **Reset Types**
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```bash
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git reset --soft HEAD~1 # Keeps staging area
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git reset HEAD~1 # Unstages, keeps files
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git reset --hard HEAD~1 # Discards everything
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```
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---
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## 11. Removing Commits
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### **Remove Local (Unpushed) Commit**
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```bash
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# Soft reset (interactive rebase recommended)
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git reset --soft HEAD~1
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# Interactive rebase for multiple commits
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git rebase -i HEAD~3
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# Change 'pick' to 'drop' or delete line
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```
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### **Remove Pushed Commit from Remote**
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**⚠️ DANGER: Rewrites shared history**
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```bash
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# 1. Reset locally
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git reset --hard HEAD~1
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# 2. Force push (collaborators must coordinate)
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git push --force-with-lease origin main
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# 3. Alternative: Safer revert
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git revert HEAD # Creates undoing commit
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git push
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```
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**Team Coordination Required:**
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```
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1. Notify team before force push
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2. Team runs: git fetch && git reset --hard origin/main
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3. Use revert for shared production branches
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```
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### **Remove Specific Pushed Commit**
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```bash
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# Interactive rebase
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git rebase -i <commit-before-target>~1
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# Or create revert
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git revert <specific-commit-hash>
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```
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---
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## 12. Stash Operations
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**Temporary Storage:**
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```bash
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git stash push -m "WIP: API changes"
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git stash list
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git stash apply stash@{0} # Keep stash
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git stash pop # Apply and remove
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```
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---
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## 13. Tags and Releases
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### **Tag Management**
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```bash
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# Lightweight tag
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git tag v1.2.3
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# Annotated tag (recommended)
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git tag -a v1.2.3 -m "Release v1.2.3"
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# Push tags
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git push origin --tags
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```
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---
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## 14. .gitignore Management
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**Create/Update:**
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```bash
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touch .gitignore
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```
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**Common Patterns:**
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```
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# Dependencies
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node_modules/
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vendor/
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# Logs
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*.log
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logs/
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# Environment
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.env
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*.env.local
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# OS
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.DS_Store
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Thumbs.db
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```
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**Apply Existing .gitignore:**
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```bash
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git rm -r --cached .
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git add . && git commit -m "Apply .gitignore"
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```
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---
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## 15. Configuration and Aliases
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### **Editor and Pager**
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```bash
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git config --global core.editor "code --wait"
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```
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### **Productivity Aliases**
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```bash
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git config --global alias.st "status"
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git config --global alias.co "checkout"
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git config --global alias.br "branch -v"
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git config --global alias.cm "!f() { git add -A && git commit -m \"$@\"; }; f"
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```
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---
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## 16. Troubleshooting and Recovery
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### **Common Recovery**
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```bash
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# View all history (including resets)
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git reflog
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# Recover deleted branch
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git checkout -b recovery-branch <commit-hash>
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# Fix detached HEAD
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git checkout main
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```
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---
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## 17. Repository Cloning
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```bash
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# Standard clone
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git clone <url>
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# Specific branch
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git clone -b develop <url>
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# Shallow clone (history limited)
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git clone --depth 1 <url>
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```
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---
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## Key Git Concepts Explained
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| Concept | Definition | Importance |
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|---------|------------|-----------|
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| **HEAD** | Current commit/branch pointer | Always points to active commit |
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| **Index/Staging** | Intermediate area between working dir and repo | Prepares exact commit content |
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| **Fast-forward** | Linear merge without merge commit | Clean history |
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| **Detached HEAD** | HEAD points directly to commit | Use for inspection, create branch to save work |
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| **Reflog** | Local history of HEAD movements | Recovery lifeline |
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| **Force Push** | Overwrites remote history | Use only with team coordination |
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**Document Version: 2.0**
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*Optimized for DevOps workflows, CI/CD integration, and team collaboration* |