Add repository synchronization functionality

- Create sync package to handle git repository synchronization
- Implement multi-organization sync with branch tracking
- Add merge conflict detection and error handling
- Support cloning, fetching, merging, and pushing across all remotes
- Add --sync flag to synchronize repositories
- Add --work-dir flag for working directory specification
- Create test infrastructure with setup and conflict test scripts
- Update config validation to support file:// URLs
- Add comprehensive .gitignore entries for test artifacts

The sync package automatically:
- Clones repositories if not present
- Fetches updates from all configured organizations
- Merges changes from all remotes for each branch
- Pushes synchronized changes to all organizations
- Detects and reports merge conflicts for manual resolution

Test with: ./test/setup_test_repos.sh && ./gitsyncer --config test/test-config.json --sync test-repo

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

2 files changed, 149 insertions, 0 deletions

diff --git a/test/setup_test_repos.sh b/test/setup_test_repos.sh
new file mode 100755
index 0000000..786b3f3
--- /dev/null
+++ b/test/setup_test_repos.sh
@@ -0,0 +1,107 @@
+#!/bin/bash
+
+# Setup script for creating test git repositories
+set -e
+
+echo "Setting up test repositories..."
+
+# Create test directory structure
+TEST_DIR="$(cd "$(dirname "$0")" && pwd)"
+REPOS_DIR="$TEST_DIR/repos"
+mkdir -p "$REPOS_DIR"
+
+# Create two bare repositories (simulating remote repos)
+REPO1_DIR="$REPOS_DIR/org1"
+REPO2_DIR="$REPOS_DIR/org2"
+
+# Clean up if they exist
+rm -rf "$REPO1_DIR" "$REPO2_DIR"
+mkdir -p "$REPO1_DIR" "$REPO2_DIR"
+
+# Initialize bare repositories
+echo "Creating bare repository in org1..."
+cd "$REPO1_DIR"
+git init --bare test-repo.git
+
+echo "Creating bare repository in org2..."
+cd "$REPO2_DIR"
+git init --bare test-repo.git
+
+# Create a temporary working directory to add initial content
+WORK_DIR="$REPOS_DIR/work"
+rm -rf "$WORK_DIR"
+mkdir -p "$WORK_DIR"
+
+# Clone from org1 and add initial content
+echo "Adding initial content..."
+cd "$WORK_DIR"
+git clone "$REPO1_DIR/test-repo.git"
+cd test-repo
+
+# Create initial files
+echo "# Test Repository" > README.md
+echo "This is a test repository for gitsyncer" >> README.md
+
+mkdir -p src
+echo "package main
+
+import \"fmt\"
+
+func main() {
+    fmt.Println(\"Hello from test repo!\")
+}" > src/main.go
+
+# Create initial commit
+git add .
+git commit -m "Initial commit"
+
+# Create develop branch
+git checkout -b develop
+echo "Development branch" > DEVELOP.md
+git add DEVELOP.md
+git commit -m "Add develop branch marker"
+
+# Create feature branch
+git checkout -b feature/test-feature
+echo "Feature content" > feature.txt
+git add feature.txt
+git commit -m "Add feature"
+
+# Push all branches to org1
+git push origin main
+git push origin develop
+git push origin feature/test-feature
+
+# Add org2 as remote and push only main branch initially
+git remote add org2 "$REPO2_DIR/test-repo.git"
+git checkout main
+git push org2 main
+
+# Clean up work directory
+cd "$TEST_DIR"
+rm -rf "$WORK_DIR"
+
+# Create test config file
+echo "Creating test configuration..."
+cat > "$TEST_DIR/test-config.json" << EOF
+{
+  "organizations": [
+    {
+      "host": "file://$REPO1_DIR",
+      "name": ""
+    },
+    {
+      "host": "file://$REPO2_DIR",
+      "name": ""
+    }
+  ]
+}
+EOF
+
+echo "Test setup complete!"
+echo ""
+echo "Repository structure:"
+echo "- org1/test-repo.git: Has main, develop, and feature/test-feature branches"
+echo "- org2/test-repo.git: Has only main branch"
+echo ""
+echo "Test config file created at: $TEST_DIR/test-config.json"
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diff --git a/test/test_conflict.sh b/test/test_conflict.sh
new file mode 100755
index 0000000..d63375c
--- /dev/null
+++ b/test/test_conflict.sh
@@ -0,0 +1,42 @@
+#!/bin/bash
+
+# Test script to demonstrate merge conflict handling
+set -e
+
+echo "Testing merge conflict detection..."
+
+TEST_DIR="$(cd "$(dirname "$0")" && pwd)"
+REPOS_DIR="$TEST_DIR/repos"
+WORK_DIR="$REPOS_DIR/conflict-work"
+
+# Clean up and create work directories
+rm -rf "$WORK_DIR"
+mkdir -p "$WORK_DIR"
+
+# Clone both repos to create conflicting changes
+echo "Creating conflicting changes in org1..."
+cd "$WORK_DIR"
+git clone "$REPOS_DIR/org1/test-repo.git" work1
+cd work1
+echo "Change from org1" > conflict.txt
+git add conflict.txt
+git commit -m "Add conflict.txt from org1"
+git push origin main
+
+echo "Creating conflicting changes in org2..."
+cd "$WORK_DIR"
+git clone "$REPOS_DIR/org2/test-repo.git" work2
+cd work2
+echo "Different change from org2" > conflict.txt
+git add conflict.txt
+git commit -m "Add conflict.txt from org2"
+git push origin main
+
+# Clean up work directories
+cd "$TEST_DIR"
+rm -rf "$WORK_DIR"
+
+echo ""
+echo "Conflicting changes created!"
+echo "Now run gitsyncer to see conflict detection:"
+echo "  ./gitsyncer --config test/test-config.json --sync test-repo --work-dir test/work-conflict"
\ No newline at end of file