write-tree Git Command Guide

The git write-tree command creates a tree object from the current index (staging area) state, representing the directory structure and file contents at a specific point in time. It’s a low-level plumbing command used internally by Git and in advanced scripting scenarios.

git write-tree Syntax:

git write-tree [--missing-ok] [--prefix=<prefix>]

Options:

Option	Description
--missing-ok	Allow missing objects in the tree
--prefix=<prefix>	Write tree object for subdirectory

Parameters:

None

Understanding Tree Objects:

Tree Object Structure:

Git Tree Object Format:
├── Mode: File permissions (100644 for files, 100755 for executables, 040000 for subtrees)
├── Type: Object type (blob for files, tree for directories)
├── SHA-1: Hash of the referenced object
├── Name: File or directory name
└── Sorted: Entries sorted lexicographically by name

Tree Creation Process:

Index to Tree Conversion:
├── Index State: Current staging area contents
├── File Entries: Convert index entries to tree format
├── Directory Structure: Build hierarchical tree structure
├── SHA-1 Calculation: Hash tree object contents
├── Object Storage: Store tree in .git/objects
└── Reference Return: Return tree SHA-1 for commit creation

Tree vs Index Relationship:

Index and Tree Relationship:
├── Index: Staging area with file states
├── Tree: Immutable snapshot of directory structure
├── Commit Creation: write-tree + commit-tree = commit
├── Branch Updates: Update refs to point to new commits
└── History Building: Chain of tree objects over time

Basic Write-Tree Operations:

Create Tree from Index:

# Create tree object from current index
git write-tree

# Create tree with missing objects allowed
git write-tree --missing-ok

# Create tree for subdirectory
git write-tree --prefix=src/

Tree Creation Workflow:

# Complete workflow: index -> tree -> commit
# 1. Stage changes
git add file.txt

# 2. Create tree from index
tree_hash=$(git write-tree)
echo "Created tree: $tree_hash"

# 3. Create commit from tree
parent_commit=$(git rev-parse HEAD)
commit_hash=$(echo "Commit message" | git commit-tree $tree_hash -p $parent_commit)
echo "Created commit: $commit_hash"

# 4. Update branch reference
git update-ref refs/heads/main $commit_hash

Inspect Tree Objects:

# Show tree contents
tree_hash=$(git write-tree)
git ls-tree $tree_hash

# Compare tree with working directory
git ls-tree $tree_hash | while read -r mode type hash name; do
    if [ -f "$name" ]; then
        echo "$name: indexed"
    else
        echo "$name: missing from working directory"
    fi
done

Advanced Write-Tree Scenarios:

Custom Commit Creation:

# Create commits programmatically
create_custom_commit() {
    local message="$1"
    local parent="${2:-HEAD}"

    echo "Creating custom commit..."

    # Get parent commit info
    if [ "$parent" = "HEAD" ]; then
        parent_hash=$(git rev-parse HEAD)
    else
        parent_hash=$(git rev-parse "$parent")
    fi

    # Get author and committer info
    author_name=$(git config user.name)
    author_email=$(git config user.email)
    author_date=$(date +%s)

    committer_name="$author_name"
    committer_email="$author_email"
    committer_date="$author_date"

    # Create tree from current index
    tree_hash=$(git write-tree)
    echo "Tree hash: $tree_hash"

    # Create commit object
    commit_content="tree $tree_hash
parent $parent_hash
author $author_name <$author_email> $author_date +0000
committer $committer_name <$committer_email> $committer_date +0000

$message"

    commit_hash=$(echo "$commit_content" | git hash-object -t commit -w --stdin)
    echo "Commit hash: $commit_hash"

    # Update branch
    git update-ref refs/heads/main $commit_hash

    echo "Custom commit created successfully"
}

# Usage
create_custom_commit "Custom commit message"

Tree Manipulation and Surgery:

# Perform tree surgery operations
tree_surgery() {
    echo "Performing tree surgery..."

    # Create tree from subdirectory
    subtree_hash=$(git write-tree --prefix=src/)
    echo "Subtree hash: $subtree_hash"

    # Create new tree structure
    # This would require more complex tree manipulation
    # using git mktree for custom tree creation

    echo "Tree surgery operations:"
    echo "  - Extracted subtree: $subtree_hash"
    echo "  - Ready for further manipulation"
}

# Compare index states
compare_index_states() {
    echo "Comparing index states..."

    # Create tree from current index
    current_tree=$(git write-tree)

    # Stash current changes
    git stash

    # Create tree from clean index
    clean_tree=$(git write-tree)

    # Restore changes
    git stash pop

    echo "Current index tree: $current_tree"
    echo "Clean index tree: $clean_tree"

    if [ "$current_tree" != "$clean_tree" ]; then
        echo "Index has uncommitted changes"
    else
        echo "Index is clean"
    fi
}

# Usage
tree_surgery
compare_index_states

Automated Tree Operations:

# Automate tree creation workflows
automated_tree_operations() {
    echo "Running automated tree operations..."

    # Create timestamped tree
    timestamp=$(date +%Y%m%d-%H%M%S)
    tree_hash=$(git write-tree)

    echo "Created tree $tree_hash at $timestamp"

    # Store tree reference for later use
    echo "$timestamp $tree_hash" >> .git/tree-history

    # Create backup tree
    backup_tree="$tree_hash"
    echo "Backup tree created: $backup_tree"

    # Verify tree integrity
    if git cat-file -e "$tree_hash" 2>/dev/null; then
        echo "✓ Tree integrity verified"
    else
        echo "✗ Tree integrity check failed"
        return 1
    fi
}

# Batch tree creation
batch_tree_creation() {
    local count="$1"

    echo "Creating $count trees..."

    for i in $(seq 1 "$count"); do
        # Make some changes
        echo "Change $i" > "temp-file-$i.txt"
        git add "temp-file-$i.txt"

        # Create tree
        tree_hash=$(git write-tree)
        echo "Tree $i: $tree_hash"

        # Clean up
        rm "temp-file-$i.txt"
        git add -A
    done

    echo "Batch tree creation complete"
}

# Usage
automated_tree_operations
batch_tree_creation 5

Configuration and Best Practices:

Git Configuration for Write-Tree:

# Configure write-tree behavior
git config core.fileMode true          # Respect file permissions
git config core.ignorecase false       # Case-sensitive file handling
git config core.precomposeunicode true # Unicode normalization

# Configure index behavior
git config core.trustctime false       # Don't trust file timestamps
git config index.skipHash false        # Include all files in hash calculation

Safe Write-Tree Operations:

# Safe tree creation with validation
safe_write_tree() {
    local prefix="${1:-}"

    echo "Creating tree safely..."

    # Check if we're in a git repository
    if ! git rev-parse --git-dir >/dev/null 2>&1; then
        echo "Error: Not in a Git repository"
        return 1
    fi

    # Check index state
    if [ -z "$(git diff --cached --name-only)" ] && [ -z "$prefix" ]; then
        echo "Warning: Index is empty, tree will be minimal"
    fi

    # Create tree
    if [ -n "$prefix" ]; then
        tree_hash=$(git write-tree --prefix="$prefix" 2>/dev/null)
    else
        tree_hash=$(git write-tree 2>/dev/null)
    fi

    if [ -n "$tree_hash" ]; then
        echo "✓ Tree created: $tree_hash"

        # Verify tree
        if git cat-file -e "$tree_hash" 2>/dev/null; then
            echo "✓ Tree integrity verified"
            echo "$tree_hash"
            return 0
        else
            echo "✗ Tree verification failed"
            return 1
        fi
    else
        echo "✗ Tree creation failed"
        return 1
    fi
}

# Usage
safe_write_tree
safe_write_tree "src/"

Tree Validation and Testing:

# Validate tree objects
validate_tree() {
    local tree_hash="$1"

    echo "Validating tree: $tree_hash"

    # Check if object exists
    if ! git cat-file -e "$tree_hash" 2>/dev/null; then
        echo "✗ Tree object does not exist"
        return 1
    fi

    # Check object type
    object_type=$(git cat-file -t "$tree_hash" 2>/dev/null)
    if [ "$object_type" != "tree" ]; then
        echo "✗ Object is not a tree (type: $object_type)"
        return 1
    fi

    # Validate tree contents
    git ls-tree "$tree_hash" >/dev/null 2>&1
    if [ $? -eq 0 ]; then
        echo "✓ Tree structure is valid"
        return 0
    else
        echo "✗ Tree structure is invalid"
        return 1
    fi
}

# Test tree creation
test_tree_creation() {
    echo "Testing tree creation..."

    # Create test files
    mkdir -p test-dir
    echo "test content" > test-file.txt
    echo "subdir content" > test-dir/subfile.txt

    # Stage files
    git add test-file.txt test-dir/

    # Create tree
    tree_hash=$(git write-tree)
    echo "Test tree created: $tree_hash"

    # Validate tree
    validate_tree "$tree_hash"

    # Show tree contents
    echo "Tree contents:"
    git ls-tree -r "$tree_hash"

    # Cleanup
    rm -rf test-dir test-file.txt
    git reset HEAD

    echo "Tree creation test complete"
}

# Usage
validate_tree "abc123..."
test_tree_creation

Integration with Development Workflows:

Custom Commit Workflows:

# Custom commit creation workflows
custom_commit_workflow() {
    echo "=== Custom Commit Workflow ==="

    # Create commit with custom metadata
    create_commit_with_metadata() {
        local message="$1"
        local author="${2:-$(git config user.name)}"
        local email="${3:-$(git config user.email)}"

        echo "Creating commit with custom metadata..."

        # Create tree
        tree_hash=$(git write-tree)
        echo "Tree: $tree_hash"

        # Get parent
        parent_hash=$(git rev-parse HEAD 2>/dev/null || echo "")

        # Create commit content
        commit_content="tree $tree_hash"
        if [ -n "$parent_hash" ]; then
            commit_content="$commit_content
parent $parent_hash"
        fi

        commit_content="$commit_content
author $author <$email> $(date +%s) +0000
committer $author <$email> $(date +%s) +0000

$message"

        # Create commit object
        commit_hash=$(echo "$commit_content" | git hash-object -t commit -w --stdin)
        echo "Commit: $commit_hash"

        # Update branch
        git update-ref refs/heads/main "$commit_hash"

        echo "Custom commit created successfully"
    }

    # Create merge commit manually
    create_manual_merge_commit() {
        local branch1="$1"
        local branch2="$2"
        local message="$3"

        echo "Creating manual merge commit..."

        # Get branch commits
        commit1=$(git rev-parse "$branch1")
        commit2=$(git rev-parse "$branch2")

        echo "Merging $commit1 and $commit2"

        # Create merge tree (simplified - real merge would handle conflicts)
        # This is a basic implementation
        tree_hash=$(git write-tree)
        echo "Merge tree: $tree_hash"

        # Create merge commit
        merge_content="tree $tree_hash
parent $commit1
parent $commit2
author $(git config user.name) <$(git config user.email)> $(date +%s) +0000
committer $(git config user.name) <$(git config user.email)> $(date +%s) +0000

$message"

        merge_hash=$(echo "$merge_content" | git hash-object -t commit -w --stdin)
        echo "Merge commit: $merge_hash"

        # Update branch
        git update-ref refs/heads/main "$merge_hash"

        echo "Manual merge commit created"
    }

    # Interactive custom workflow
    echo "Custom Commit Workflow Options:"
    echo "1. Create commit with custom metadata"
    echo "2. Create manual merge commit"

    read -p "Select option (1-2): " option

    case "$option" in
        1)
            read -p "Commit message: " message
            read -p "Author name (default: current): " author
            read -p "Author email (default: current): " email
            create_commit_with_metadata "$message" "${author:-}" "${email:-}"
            ;;
        2)
            read -p "Branch 1: " branch1
            read -p "Branch 2: " branch2
            read -p "Merge message: " message
            create_manual_merge_commit "$branch1" "$branch2" "$message"
            ;;
    esac
}

custom_commit_workflow

Repository Surgery and Repair:

# Repository surgery using write-tree
repository_surgery() {
    echo "=== Repository Surgery with Write-Tree ==="

    # Fix corrupted commit
    fix_corrupted_commit() {
        local bad_commit="$1"

        echo "Attempting to fix corrupted commit: $bad_commit"

        # Get commit info
        commit_info=$(git cat-file -p "$bad_commit" 2>/dev/null)
        if [ $? -ne 0 ]; then
            echo "Cannot read commit $bad_commit"
            return 1
        fi

        # Extract tree from commit
        tree_hash=$(echo "$commit_info" | grep "^tree" | cut -d' ' -f2)
        echo "Original tree: $tree_hash"

        # Create new tree from current index
        # (Assuming we've staged the corrected content)
        new_tree_hash=$(git write-tree)
        echo "New tree: $new_tree_hash"

        # Create new commit with corrected tree
        parent_info=$(echo "$commit_info" | grep "^parent" | head -1 | cut -d' ' -f2)
        author_info=$(echo "$commit_info" | grep "^author")
        committer_info=$(echo "$commit_info" | grep "^committer")
        commit_message=$(echo "$commit_info" | sed -n '/^$/,$p' | tail -n +2)

        new_commit_content="tree $new_tree_hash
$parent_info
$author_info
$committer_info

$commit_message"

        new_commit_hash=$(echo "$new_commit_content" | git hash-object -t commit -w --stdin)
        echo "New commit: $new_commit_hash"

        # Replace the corrupted commit
        git update-ref refs/heads/main "$new_commit_hash"

        echo "Corrupted commit fixed"
    }

    # Extract subtree for separate repository
    extract_subtree() {
        local subtree_path="$1"
        local target_repo="$2"

        echo "Extracting subtree $subtree_path to $target_repo"

        # Create tree for subtree
        subtree_hash=$(git write-tree --prefix="$subtree_path/")
        echo "Subtree hash: $subtree_hash"

        # Initialize target repository
        mkdir -p "$target_repo"
        cd "$target_repo"
        git init

        # Create initial commit with subtree content
        echo "Initial commit from extracted subtree" | git commit-tree "$subtree_hash" | git update-ref refs/heads/main

        cd -
        echo "Subtree extracted to $target_repo"
    }

    # Interactive repository surgery
    echo "Repository Surgery Options:"
    echo "1. Fix corrupted commit"
    echo "2. Extract subtree to new repository"

    read -p "Select option (1-2): " option

    case "$option" in
        1)
            read -p "Corrupted commit hash: " bad_commit
            fix_corrupted_commit "$bad_commit"
            ;;
        2)
            read -p "Subtree path: " subtree_path
            read -p "Target repository path: " target_repo
            extract_subtree "$subtree_path" "$target_repo"
            ;;
    esac
}

repository_surgery

Automated Backup and Recovery:

# Automated tree-based backup system
tree_backup_system() {
    echo "=== Tree-Based Backup System ==="

    # Create timestamped backup
    create_tree_backup() {
        local backup_name="${1:-backup-$(date +%Y%m%d-%H%M%S)}"

        echo "Creating tree backup: $backup_name"

        # Create tree from current index
        tree_hash=$(git write-tree)
        echo "Tree hash: $tree_hash"

        # Store backup metadata
        backup_dir=".git/tree-backups"
        mkdir -p "$backup_dir"

        cat > "$backup_dir/$backup_name.meta" << EOF
Backup: $backup_name
Created: $(date)
Tree: $tree_hash
Branch: $(git branch --show-current)
Commit: $(git rev-parse HEAD)
Files: $(git ls-files | wc -l)
EOF

        # Create backup of tree object
        git cat-file -p "$tree_hash" > "$backup_dir/$backup_name.tree"

        echo "Backup created: $backup_name"
    }

    # Restore from tree backup
    restore_tree_backup() {
        local backup_name="$1"

        echo "Restoring from tree backup: $backup_name"

        backup_dir=".git/tree-backups"
        meta_file="$backup_dir/$backup_name.meta"

        if [ ! -f "$meta_file" ]; then
            echo "Backup not found: $backup_name"
            return 1
        fi

        # Read backup metadata
        tree_hash=$(grep "^Tree:" "$meta_file" | cut -d' ' -f2)
        original_commit=$(grep "^Commit:" "$meta_file" | cut -d' ' -f2)

        echo "Restoring tree: $tree_hash"

        # Reset index to tree state
        git read-tree "$tree_hash"

        # Create commit from restored tree
        commit_message="Restore from tree backup: $backup_name"
        commit_hash=$(echo "$commit_message" | git commit-tree "$tree_hash" -p "$original_commit")

        echo "Restored commit: $commit_hash"
    }

    # List available backups
    list_tree_backups() {
        echo "Available tree backups:"

        backup_dir=".git/tree-backups"

        if [ -d "$backup_dir" ]; then
            for meta_file in "$backup_dir"/*.meta; do
                if [ -f "$meta_file" ]; then
                    backup_name=$(basename "$meta_file" .meta)
                    created=$(grep "^Created:" "$meta_file" | cut -d' ' -f2-)
                    tree_hash=$(grep "^Tree:" "$meta_file" | cut -d' ' -f2)

                    echo "  $backup_name - $created - $tree_hash"
                fi
            done
        else
            echo "  No backups found"
        fi
    }

    # Interactive backup system
    echo "Tree Backup System Options:"
    echo "1. Create tree backup"
    echo "2. Restore from backup"
    echo "3. List available backups"

    read -p "Select option (1-3): " option

    case "$option" in
        1)
            read -p "Backup name (default: auto-generated): " backup_name
            create_tree_backup "${backup_name:-}"
            ;;
        2)
            list_tree_backups
            read -p "Backup name to restore: " backup_name
            restore_tree_backup "$backup_name"
            ;;
        3) list_tree_backups ;;
    esac
}

tree_backup_system

Troubleshooting Common Issues:

Index State Issues:

# Troubleshoot index state problems
diagnose_index_issues() {
    echo "Diagnosing index state issues..."

    # Check index file
    if [ -f ".git/index" ]; then
        echo "✓ Index file exists"

        # Check index size
        index_size=$(stat -f%z .git/index 2>/dev/null || stat -c%s .git/index)
        echo "Index size: $index_size bytes"
    else
        echo "✗ Index file missing"
        return 1
    fi

    # Check staged files
    staged_count=$(git diff --cached --name-only | wc -l)
    echo "Staged files: $staged_count"

    if [ "$staged_count" -eq 0 ]; then
        echo "⚠ No files staged - tree will be empty or unchanged"
    fi

    # Check for conflicts
    conflict_count=$(git diff --name-only | grep "^[^ ]*U[^ ]*$" | wc -l)
    if [ "$conflict_count" -gt 0 ]; then
        echo "⚠ $conflict_count files have merge conflicts"
        echo "Resolve conflicts before creating tree"
    fi

    # Check index integrity
    if git ls-files --stage >/dev/null 2>&1; then
        echo "✓ Index integrity verified"
    else
        echo "✗ Index corruption detected"
        return 1
    fi
}

# Fix index issues
fix_index_issues() {
    echo "Attempting to fix index issues..."

    # Reset index to HEAD
    echo "Resetting index to HEAD..."
    git reset --hard HEAD

    # Clear index
    echo "Clearing index..."
    rm -f .git/index

    # Rebuild index
    echo "Rebuilding index..."
    git add .

    # Verify fix
    if git ls-files --stage >/dev/null 2>&1; then
        echo "✓ Index rebuilt successfully"
    else
        echo "✗ Index rebuild failed"
        return 1
    fi
}

# Usage
diagnose_index_issues
fix_index_issues

Tree Creation Failures:

# Troubleshoot tree creation failures
diagnose_tree_creation_issues() {
    echo "Diagnosing tree creation issues..."

    # Test basic tree creation
    if tree_hash=$(git write-tree 2>&1); then
        echo "✓ Basic tree creation works: $tree_hash"
    else
        echo "✗ Tree creation failed: $tree_hash"
        return 1
    fi

    # Test with missing-ok option
    if missing_tree=$(git write-tree --missing-ok 2>&1); then
        echo "✓ Missing-ok tree creation works: $missing_tree"
    else
        echo "✗ Missing-ok tree creation failed"
    fi

    # Test prefix option
    if [ -d "src" ]; then
        if prefix_tree=$(git write-tree --prefix=src/ 2>&1); then
            echo "✓ Prefix tree creation works: $prefix_tree"
        else
            echo "✗ Prefix tree creation failed"
        fi
    else
        echo "⚠ No src/ directory for prefix testing"
    fi

    # Check Git version
    git_version=$(git --version | sed 's/git version //')
    echo "Git version: $git_version"

    # Version-specific checks
    if [[ "$git_version" =~ ^2\.[0-9]+ ]]; then
        echo "✓ Modern Git version"
    else
        echo "⚠ Older Git version detected"
    fi
}

# Handle missing objects
handle_missing_objects() {
    echo "Handling missing objects in tree creation..."

    # Find missing objects
    echo "Checking for missing objects..."
    git fsck --unreachable 2>&1 | grep "missing" | head -5

    # Attempt to create tree with missing-ok
    echo "Attempting tree creation with --missing-ok..."
    tree_hash=$(git write-tree --missing-ok 2>&1)

    if [ $? -eq 0 ]; then
        echo "✓ Tree created with missing objects: $tree_hash"
        echo "Note: This tree contains references to missing objects"
    else
        echo "✗ Tree creation still failed"
        return 1
    fi
}

# Usage
diagnose_tree_creation_issues
handle_missing_objects

Repository State Issues:

# Troubleshoot repository state problems
diagnose_repo_state_issues() {
    echo "Diagnosing repository state issues..."

    # Check repository validity
    if ! git rev-parse --git-dir >/dev/null 2>&1; then
        echo "✗ Not in a valid Git repository"
        return 1
    fi

    # Check HEAD
    if git rev-parse HEAD >/dev/null 2>&1; then
        echo "✓ HEAD exists"
        head_commit=$(git rev-parse HEAD)
        echo "HEAD commit: $head_commit"
    else
        echo "⚠ No commits yet (HEAD not set)"
    fi

    # Check refs
    branch_count=$(git branch | wc -l)
    tag_count=$(git tag | wc -l)
    echo "Branches: $branch_count, Tags: $tag_count"

    # Check object database
    object_count=$(find .git/objects -type f | wc -l)
    echo "Objects in database: $object_count"

    # Check for corruption
    if git fsck --full >/dev/null 2>&1; then
        echo "✓ Repository integrity verified"
    else
        echo "✗ Repository corruption detected"
        return 1
    fi

    # Check working directory state
    if [ -n "$(git status --porcelain)" ]; then
        echo "⚠ Working directory has uncommitted changes"
        modified_count=$(git status --porcelain | grep "^ M" | wc -l)
        added_count=$(git status --porcelain | grep "^A" | wc -l)
        deleted_count=$(git status --porcelain | grep "^D" | wc -l)
        echo "Modified: $modified_count, Added: $added_count, Deleted: $deleted_count"
    else
        echo "✓ Working directory is clean"
    fi
}

# Fix repository state issues
fix_repo_state_issues() {
    echo "Attempting to fix repository state issues..."

    # Clean uncommitted changes if safe
    if [ -n "$(git status --porcelain)" ]; then
        echo "Cleaning uncommitted changes..."
        git reset --hard HEAD
        git clean -fd
        echo "✓ Repository state cleaned"
    fi

    # Run maintenance
    echo "Running repository maintenance..."
    git gc --aggressive
    git fsck --full

    # Verify fix
    if git fsck --full >/dev/null 2>&1; then
        echo "✓ Repository state fixed"
    else
        echo "✗ Repository state still problematic"
        return 1
    fi
}

# Usage
diagnose_repo_state_issues
fix_repo_state_issues

Performance and Memory Issues:

# Troubleshoot performance issues
diagnose_performance_issues() {
    echo "Diagnosing write-tree performance issues..."

    # Measure basic operation time
    echo "Measuring write-tree performance..."
    time_start=$(date +%s.%3N)
    tree_hash=$(git write-tree >/dev/null 2>&1)
    time_end=$(date +%s.%3N)

    # Calculate duration
    duration=$(echo "$time_end - $time_start" | bc 2>/dev/null || echo "0")
    echo "Tree creation time: ${duration}s"

    if (( $(echo "$duration > 5" | bc -l 2>/dev/null || echo "0") )); then
        echo "⚠ Slow tree creation detected"
    else
        echo "✓ Tree creation performance acceptable"
    fi

    # Check index size
    index_entries=$(git ls-files | wc -l)
    echo "Index entries: $index_entries"

    if [ "$index_entries" -gt 10000 ]; then
        echo "⚠ Large index detected - may impact performance"
    fi

    # Check memory usage
    echo "Checking memory usage..."
    if command -v ps >/dev/null 2>&1; then
        # This would require running git in a monitored environment
        echo "Memory monitoring requires external tools"
    fi

    # Performance recommendations
    echo "Performance recommendations:"
    echo "- Keep index size reasonable (< 10,000 entries)"
    echo "- Use SSD storage for .git directory"
    echo "- Run 'git gc' regularly"
    echo "- Avoid very deep directory structures"
}

# Optimize write-tree performance
optimize_write_tree_performance() {
    echo "Optimizing write-tree performance..."

    # Run garbage collection
    echo "Running garbage collection..."
    git gc --aggressive --prune=now

    # Optimize index
    echo "Optimizing index..."
    git update-index --refresh

    # Defragment objects
    echo "Defragmenting objects..."
    git repack -a -d --depth=250 --window=250

    # Update references
    echo "Updating references..."
    git update-ref --no-deref -d refs/remotes/origin

    echo "Performance optimization complete"
}

# Usage
diagnose_performance_issues
optimize_write_tree_performance

Caution

git write-tree creates immutable tree objects. Changes to the index after tree creation don’t affect existing trees. Use —missing-ok carefully as it allows trees with broken references.

Real-World Usage Examples:

Advanced Repository Management:

#!/bin/bash
# Advanced repository management with write-tree

advanced_repo_management() {
    echo "=== Advanced Repository Management ==="

    # Create atomic commits
    create_atomic_commits() {
        echo "Creating atomic commits..."

        # Stage related changes together
        git add src/components/
        tree1=$(git write-tree)
        echo "UI components tree: $tree1"

        git add src/api/
        tree2=$(git write-tree)
        echo "API changes tree: $tree2"

        git add tests/
        tree3=$(git write-tree)
        echo "Test updates tree: $tree3"

        # Create separate commits for each atomic change
        parent=$(git rev-parse HEAD)

        commit1=$(echo "feat: update UI components" | git commit-tree "$tree1" -p "$parent")
        commit2=$(echo "feat: update API endpoints" | git commit-tree "$tree2" -p "$commit1")
        commit3=$(echo "test: update test coverage" | git commit-tree "$tree3" -p "$commit2")

        # Update branch
        git update-ref refs/heads/main "$commit3"

        echo "Atomic commits created successfully"
    }

    # Implement tree-based branching
    tree_based_branching() {
        echo "Implementing tree-based branching..."

        # Create feature branch from specific tree state
        base_tree=$(git write-tree)
        echo "Base tree: $base_tree"

        # Create branch pointing to commit with this tree
        branch_commit=$(echo "feat: start new feature branch" | git commit-tree "$base_tree")
        git update-ref refs/heads/feature/new-feature "$branch_commit"

        echo "Feature branch created from tree: $base_tree"
    }

    # Tree-based deployment
    tree_based_deployment() {
        local environment="$1"

        echo "Performing tree-based deployment to $environment..."

        # Create deployment tree
        deploy_tree=$(git write-tree --prefix=deploy/)
        echo "Deployment tree: $deploy_tree"

        # Create deployment commit
        deploy_commit=$(echo "deploy: $environment deployment" | git commit-tree "$deploy_tree")
        echo "Deployment commit: $deploy_commit"

        # Tag deployment
        git tag "deploy/$environment-$(date +%Y%m%d-%H%M%S)" "$deploy_commit"

        echo "Deployment prepared for $environment"
    }

    # Interactive advanced management
    echo "Advanced Repository Management Options:"
    echo "1. Create atomic commits"
    echo "2. Tree-based branching"
    echo "3. Tree-based deployment"

    read -p "Select option (1-3): " option

    case "$option" in
        1) create_atomic_commits ;;
        2) tree_based_branching ;;
        3)
            read -p "Environment: " env
            tree_based_deployment "$env"
            ;;
    esac
}

advanced_repo_management

Custom Git Operations:

# Custom Git operations using write-tree
custom_git_operations() {
    echo "=== Custom Git Operations ==="

    # Implement custom merge strategy
    custom_merge_strategy() {
        local branch1="$1"
        local branch2="$2"

        echo "Implementing custom merge strategy..."

        # Get trees from both branches
        git checkout "$branch1"
        tree1=$(git write-tree)

        git checkout "$branch2"
        tree2=$(git write-tree)

        echo "Branch trees: $tree1, $tree2"

        # Custom merge logic would go here
        # For now, just create a simple merge
        merged_tree=$(git write-tree)  # Simplified

        # Create merge commit
        merge_commit=$(echo "Custom merge of $branch1 and $branch2" | git commit-tree "$merged_tree" -p "$branch1" -p "$branch2")

        echo "Custom merge commit: $merge_commit"
    }

    # Create annotated snapshots
    create_snapshot() {
        local snapshot_name="$1"

        echo "Creating annotated snapshot: $snapshot_name"

        # Create tree from current state
        snapshot_tree=$(git write-tree)
        echo "Snapshot tree: $snapshot_tree"

        # Create annotated tag for snapshot
        git tag -a "snapshot/$snapshot_name" -m "Snapshot: $snapshot_name

Created: $(date)
Tree: $snapshot_tree
Files: $(git ls-tree -r "$snapshot_tree" | wc -l)

This snapshot preserves the current state for future reference."

        echo "Snapshot created: snapshot/$snapshot_name"
    }

    # Tree diffing and comparison
    tree_diff() {
        local tree1="$1"
        local tree2="$2"

        echo "Comparing trees: $tree1 vs $tree2"

        # Get file lists
        files1=$(git ls-tree -r "$tree1" | awk '{print $4}' | sort)
        files2=$(git ls-tree -r "$tree2" | awk '{print $4}' | sort)

        # Find differences
        added=$(comm -23 <(echo "$files2") <(echo "$files1"))
        removed=$(comm -13 <(echo "$files2") <(echo "$files1"))
        common=$(comm -12 <(echo "$files1") <(echo "$files2"))

        echo "Added files:"
        echo "$added" | sed 's/^/+ /'

        echo "Removed files:"
        echo "$removed" | sed 's/^/- /'

        echo "Common files: $(echo "$common" | wc -l)"
    }

    # Interactive custom operations
    echo "Custom Git Operations Options:"
    echo "1. Custom merge strategy"
    echo "2. Create snapshot"
    echo "3. Tree diff"

    read -p "Select option (1-3): " option

    case "$option" in
        1)
            read -p "Branch 1: " branch1
            read -p "Branch 2: " branch2
            custom_merge_strategy "$branch1" "$branch2"
            ;;
        2)
            read -p "Snapshot name: " snapshot_name
            create_snapshot "$snapshot_name"
            ;;
        3)
            read -p "Tree 1: " tree1
            read -p "Tree 2: " tree2
            tree_diff "$tree1" "$tree2"
            ;;
    esac
}

custom_git_operations

Repository Analysis and Forensics:

# Repository analysis using write-tree
tree_based_analysis() {
    echo "=== Tree-Based Repository Analysis ==="

    # Analyze tree evolution
    analyze_tree_evolution() {
        echo "Analyzing tree evolution over time..."

        # Get recent commits and their trees
        git log --oneline -10 | while read -r commit_hash commit_msg; do
            tree_hash=$(git show --no-patch --format="%T" "$commit_hash")
            file_count=$(git ls-tree -r "$tree_hash" | wc -l)

            echo "$commit_hash - $commit_msg"
            echo "  Tree: $tree_hash, Files: $file_count"
        done
    }

    # Detect file movements
    detect_file_movements() {
        echo "Detecting file movements across trees..."

        # Compare consecutive trees
        previous_tree=""
        git log --oneline | while read -r commit_hash commit_msg; do
            current_tree=$(git show --no-patch --format="%T" "$commit_hash")

            if [ -n "$previous_tree" ] && [ "$current_tree" != "$previous_tree" ]; then
                echo "Tree change in $commit_hash: $previous_tree -> $current_tree"

                # Compare file lists (simplified)
                prev_files=$(git ls-tree -r "$previous_tree" | wc -l)
                curr_files=$(git ls-tree -r "$current_tree" | wc -l)

                echo "  Files: $prev_files -> $curr_files"
            fi

            previous_tree="$current_tree"
        done
    }

    # Tree size analysis
    analyze_tree_sizes() {
        echo "Analyzing tree sizes..."

        git log --oneline | while read -r commit_hash commit_msg; do
            tree_hash=$(git show --no-patch --format="%T" "$commit_hash")

            # Calculate tree size (simplified)
            tree_size=$(git ls-tree -r "$tree_hash" | awk '{sum += $3} END {print sum}')
            file_count=$(git ls-tree -r "$tree_hash" | wc -l)

            echo "$commit_hash: $file_count files, $tree_size bytes"
        done | head -10
    }

    # Generate tree analysis report
    generate_tree_report() {
        echo "Generating tree analysis report..."

        cat > tree-analysis-report.md << EOF
# Tree Analysis Report

Generated: $(date)
Repository: $(basename "$(pwd)")

## Tree Evolution
EOF

        analyze_tree_evolution >> tree-analysis-report.md

        cat >> tree-analysis-report.md << EOF

## File Movement Detection
EOF

        detect_file_movements >> tree-analysis-report.md

        cat >> tree-analysis-report.md << EOF

## Tree Size Analysis
EOF

        analyze_tree_sizes >> tree-analysis-report.md

        echo "Tree analysis report generated: tree-analysis-report.md"
    }

    # Run comprehensive analysis
    analyze_tree_evolution
    echo
    detect_file_movements
    echo
    analyze_tree_sizes
    echo
    generate_tree_report
}

# Usage
tree_based_analysis

Tip

Use git write-tree to create immutable snapshots of your index state. Combine with git commit-tree for custom commit creation. Use —prefix to create trees for subdirectories.

What’s the difference between git write-tree and git commit?

git write-tree creates a tree object from the index; git commit creates a commit object that references a tree plus metadata.

How do I create a tree from only staged changes?

git write-tree creates a tree from the current index state (staging area).

Can write-tree handle empty directories?

No, Git doesn’t store empty directories. Only files and subtrees are included in tree objects.

What’s the —missing-ok option for?

Allows creating trees that reference missing objects, useful for incomplete or corrupted repositories.

How do I inspect a tree object?

git ls-tree shows the contents of a tree object.

Can write-tree work with uncommitted changes?

No, it only uses the staged changes in the index. Uncommitted changes in working directory are ignored.

What’s the relationship between trees and commits?

Each commit references exactly one tree object that represents the directory structure at that point in time.

How do I create a commit from a tree?

Use git commit-tree -m “message” to create a commit object.

Can write-tree create trees for subdirectories?

Yes, use —prefix=/ to create a tree containing only the specified subdirectory.

What’s the performance impact of write-tree?

Minimal for typical repositories; scales with index size and number of files.

Applications of the git write-tree command

1. Custom Commit Creation: Build commits programmatically with specific tree states
2. Repository Surgery: Fix corrupted commits by creating new trees
3. Tree Manipulation: Extract subtrees and manipulate directory structures
4. Backup and Recovery: Create immutable snapshots for backup purposes
5. Atomic Operations: Ensure related changes are grouped in single trees
6. Deployment Preparation: Create deployment-specific tree states
7. Repository Analysis: Analyze how directory structures evolve over time
8. Advanced Workflows: Support complex Git operations and automation