write a small zsh function that…

Here's a small zsh function that can convert between IPFS CID v0 and v1:

```zsh
# Convert between IPFS CID v0 and v1
cid_convert() {
    local cid="$1"
    
    if [[ -z "$cid" ]]; then
        echo "Usage: cid_convert <CID>"
        echo "Converts between IPFS CID v0 and v1 formats"
        return 1
    fi
    
    # Check if ipfs command is available
    if ! command -v ipfs &> /dev/null; then
        echo "Error: ipfs command not found. Please install IPFS."
        return 1
    fi
    
    # Detect CID version and convert
    if [[ "$cid" =~ ^Qm[1-9A-HJ-NP-Za-km-z]{44}$ ]]; then
        # CID v0 format (starts with Qm, 46 chars total)
        echo "Converting CID v0 to v1..."
        ipfs cid format -v 1 -b base32 "$cid" 2>/dev/null || {
            echo "Error: Invalid CID v0 or conversion failed"
            return 1
        }
    elif [[ "$cid" =~ ^b[a-z2-7]{58}$ ]] || [[ "$cid" =~ ^[a-z2-7]+$ && ${#cid} -gt 46 ]]; then
        # CID v1 format (base32 encoded, starts with 'b' or longer base32 string)
        echo "Converting CID v1 to v0..."
        ipfs cid format -v 0 "$cid" 2>/dev/null || {
            echo "Error: Invalid CID v1 or conversion failed (note: not all v1 CIDs can be converted to v0)"
            return 1
        }
    else
        echo "Error: Unrecognized CID format"
        echo "Expected:"
        echo "  - CID v0: Qm... (46 characters, base58)"
        echo "  - CID v1: b... (base32) or other multibase formats"
        return 1
    fi
}
```

You can also create a more compact version if you prefer:

```zsh
# Compact version
cid_convert() {
    [[ -z "$1" ]] && { echo "Usage: cid_convert <CID>"; return 1; }
    command -v ipfs >/dev/null || { echo "Error: ipfs not found"; return 1; }
    
    if [[ "$1" =~ ^Qm[1-9A-HJ-NP-Za-km-z]{44}$ ]]; then
        ipfs cid format -v 1 -b base32 "$1"
    else
        ipfs cid format -v 0 "$1" 2>/dev/null || echo "Error: Conversion failed"
    fi
}
```

**Usage:**

Add the function to your `~/.zshrc` file, then:

```bash
# Convert v0 to v1
cid_convert QmYourCIDv0Here

# Convert v1 to v0  
cid_convert bafybeiyourCIDv1here
```

**Features:**
- Automatically detects CID version based on format
- Uses IPFS built-in conversion tools for reliability
- Includes error handling for invalid CIDs
- Provides helpful usage information

**Requirements:**
- IPFS must be installed and available in PATH
- Note that not all CID v1s can be converted to v0 (only SHA-256 hashed content)