feat: Add comprehensive Git credential manager for Linux

- Automatic detection of available credential helpers
- Smart selection of most secure available option
- Platform-specific support (Libsecret, Keychain, Windows Credential Store)
- Support for Cache, Store, and Git Credential Manager
- Custom credential helper configuration
- New UI in Preferences with dropdown selector
- Detailed documentation for setup and troubleshooting

This solves the common Linux problem where users have to repeatedly
enter credentials for each Git operation. The system now auto-detects
and configures the best available credential helper.

Closes issues related to credential persistence on Linux

Author: biancode

RELEASE_NOTES.md

@@ -1,6 +1,25 @@
 # SourceGit Iniationware Edition - Release Notes
 
-## Version 2025.34-IW.3
+## Version 2025.34-IW.4
+
+### What's New in IW.4
+This release introduces comprehensive Git credential management to solve the common problem on Linux where users have to repeatedly enter credentials. The new system auto-detects and configures the best available credential helper for your platform.
+
+### Major New Feature: Git Credential Manager
+- **Automatic Detection**: Discovers all available credential helpers on your system
+- **Smart Selection**: Automatically chooses the most secure option available
+- **Platform-Specific Support**: 
+  - Linux: Libsecret (GNOME Keyring/KWallet) support
+  - macOS: Native Keychain integration
+  - Windows: Credential Store integration
+- **Multiple Options**: Support for Cache (memory), Store (file), and Git Credential Manager
+- **Custom Helpers**: Configure any custom credential helper command
+- **User-Friendly UI**: New credential manager dropdown in Preferences → Git tab
+- **Security-First**: Prioritizes secure storage methods over convenience
+
+This feature is especially beneficial for Linux users who previously had to enter credentials repeatedly for each Git operation.
+
+## Version 2025.34-IW.3 (Previous Release)
 
 ### What's New in IW.3
 This critical patch release focuses on stability improvements, integrating important bug fixes from upstream SourceGit. These fixes address crashes, UI reliability issues, and functional improvements that significantly enhance the application's stability.

VERSION

@@ -1 +1 @@
-2025.34-IW.3
+2025.34-IW.4

docs/CREDENTIAL_MANAGER.md

@@ -0,0 +1,246 @@
+# Git Credential Manager Documentation
+
+## Overview
+
+SourceGit now includes comprehensive Git credential management to solve the common problem on Linux (and other platforms) where users have to repeatedly enter their credentials for each Git operation.
+
+## Features
+
+### Automatic Detection
+- **Auto-discovery**: Automatically detects available credential helpers on your system
+- **Smart Selection**: Chooses the most secure available option by default
+- **Cross-platform**: Works on Windows, macOS, and Linux with platform-specific optimizations
+
+### Supported Credential Helpers
+
+#### 1. **None**
+- No credential storage
+- Will prompt for credentials each time
+- Most secure but least convenient
+
+#### 2. **Git Credential Manager (GCM)**
+- Cross-platform credential manager from Microsoft
+- Supports multi-factor authentication
+- Works with GitHub, Azure DevOps, Bitbucket, and more
+- **Recommended for most users**
+
+#### 3. **Cache**
+- Stores credentials in memory temporarily
+- Default timeout: 1 hour
+- Good balance of security and convenience
+- No persistent storage on disk
+
+#### 4. **Store**
+- Saves credentials to a file on disk
+- **Warning**: Stores passwords in plain text
+- Only use on secure, single-user systems
+- File location: `~/.sourcegit/data/.git-credentials`
+
+#### 5. **Platform-Specific Options**
+
+##### Linux: Libsecret
+- Integrates with GNOME Keyring or KWallet
+- Secure encrypted storage
+- Automatically unlocked when you log in
+- **Recommended for Linux desktop users**
+
+##### macOS: Keychain
+- Uses the native macOS Keychain
+- Secure, encrypted storage
+- Integrated with system security
+- **Recommended for macOS users**
+
+##### Windows: Windows Credential Store
+- Uses Windows Credential Manager
+- Secure, encrypted storage
+- Integrated with Windows security
+- **Recommended for Windows users**
+
+#### 6. **Custom**
+- Specify your own credential helper command
+- For advanced users with specific requirements
+- Supports any git-credential-* helper
+
+## Configuration
+
+### Via UI
+
+1. Open **Preferences** (Ctrl/Cmd + ,)
+2. Navigate to the **Git** tab
+3. Find the **Credential Helper** dropdown
+4. Select your preferred credential helper
+5. For custom helpers, enter the command in the text field that appears
+
+### Automatic Configuration
+
+SourceGit automatically:
+1. Detects available credential helpers on startup
+2. Selects the most secure available option
+3. Applies the configuration to all Git operations
+
+### Priority Order
+
+When multiple helpers are available, SourceGit selects based on this priority:
+1. Git Credential Manager Core
+2. Git Credential Manager
+3. Libsecret (Linux)
+4. macOS Keychain (macOS)
+5. Windows Credential Store (Windows)
+6. Cache (memory-based)
+7. Store (file-based)
+8. None
+
+## Linux-Specific Setup
+
+### Installing Credential Helpers
+
+#### Ubuntu/Debian
+```bash
+# For Git Credential Manager
+curl -sSL https://aka.ms/gcm/linux-install-source.sh | sh
+git-credential-manager configure
+
+# For Libsecret
+sudo apt-get install libsecret-1-0 libsecret-1-dev
+sudo apt-get install git-credential-libsecret
+```
+
+#### Fedora/RHEL
+```bash
+# For Git Credential Manager
+curl -sSL https://aka.ms/gcm/linux-install-source.sh | sh
+git-credential-manager configure
+
+# For Libsecret
+sudo dnf install libsecret libsecret-devel
+sudo dnf install git-credential-libsecret
+```
+
+#### Arch Linux
+```bash
+# For Git Credential Manager
+yay -S git-credential-manager-core-bin
+
+# For Libsecret
+sudo pacman -S libsecret
+sudo pacman -S git-credential-libsecret
+```
+
+### Troubleshooting Linux Credential Issues
+
+#### Problem: Credentials not persisting
+**Solution**: 
+1. Check if a keyring daemon is running:
+   ```bash
+   ps aux | grep -E 'gnome-keyring|kwallet'
+   ```
+2. If not, start it:
+   ```bash
+   # For GNOME
+   gnome-keyring-daemon --start --daemonize
+   
+   # For KDE
+   kwalletd5 &
+   ```
+
+#### Problem: "No credential helper is configured"
+**Solution**:
+1. Open SourceGit Preferences
+2. Select a credential helper from the dropdown
+3. Restart SourceGit
+
+#### Problem: Libsecret not working
+**Solution**:
+1. Ensure libsecret is installed correctly
+2. Check if the keyring is unlocked
+3. Try using the Cache helper as a fallback
+
+## Security Recommendations
+
+### Best Practices
+
+1. **Use platform-specific secure storage** when available:
+   - Linux: Libsecret
+   - macOS: Keychain
+   - Windows: Credential Store
+
+2. **Avoid the Store helper** unless:
+   - You're on a secure, single-user system
+   - The repository contains only public data
+   - You understand the security implications
+
+3. **Use Cache for temporary access**:
+   - Good for shared systems
+   - Credentials expire after timeout
+   - No persistent storage
+
+4. **Configure timeout for Cache**:
+   - Default: 3600 seconds (1 hour)
+   - Adjust based on your security needs
+
+### Personal Access Tokens
+
+For enhanced security with services like GitHub:
+1. Use Personal Access Tokens instead of passwords
+2. Generate tokens with minimal required permissions
+3. Set expiration dates on tokens
+4. Store tokens securely using credential helpers
+
+## Implementation Details
+
+### How It Works
+
+1. **Detection Phase**: On startup, SourceGit checks for available credential helpers
+2. **Selection Phase**: Chooses the best available helper based on security and platform
+3. **Configuration Phase**: Sets the credential helper for all Git operations
+4. **Runtime Phase**: Git uses the configured helper for all remote operations
+
+### Technical Architecture
+
+The credential manager system consists of:
+- `Models/CredentialManager.cs`: Core credential manager logic
+- `Views/Preferences.axaml`: UI for credential helper selection
+- `Native/OS.cs`: Platform-specific credential helper integration
+- `Commands/Command.cs`: Git command execution with credential helper
+
+### Git Command Integration
+
+All Git commands executed by SourceGit include:
+```bash
+git -c credential.helper=[selected-helper] [command]
+```
+
+This ensures consistent credential handling across all operations.
+
+## Frequently Asked Questions
+
+### Q: Why do I still get prompted for credentials?
+**A**: This can happen if:
+- No credential helper is configured
+- The credential helper is not installed properly
+- Your stored credentials have expired
+- You're accessing a new repository/remote
+
+### Q: Is it safe to use the Store helper?
+**A**: The Store helper saves passwords in plain text. Only use it on:
+- Secure, single-user systems
+- Systems with encrypted disk storage
+- For repositories without sensitive data
+
+### Q: Can I use multiple credential helpers?
+**A**: Git supports credential helper chaining, but SourceGit currently configures one helper at a time for simplicity and predictability.
+
+### Q: How do I clear stored credentials?
+**A**: Depends on the helper:
+- **Cache**: Restart SourceGit or wait for timeout
+- **Store**: Delete `~/.git-credentials` or the configured file
+- **Libsecret/Keychain**: Use system tools to manage stored passwords
+- **GCM**: Run `git credential-manager erase`
+
+## Support
+
+If you encounter issues with credential management:
+1. Check the credential helper dropdown in Preferences
+2. Verify the helper is installed correctly
+3. Try a different credential helper
+4. Report issues at: https://github.com/sourcegit-scm/sourcegit/issues