message: use `square` boolean instead of `shape`
diff: @@ -5,18 +5,12 @@ import {space} from 'styled-system'
  import systemPropTypes from '@styled-system/prop-types'
  import theme from './theme'
  -function borderRadiusValue({size, shape}) {
  - switch (shape) {
  - case 'circle':
  - return '50%'
  - default:
  - return size <= 24 ? '5px' : '6px'
  - }
  -}
  -function borderRadius({size, shape}) {
  - return {
  - borderRadius: borderRadiusValue({size, shape})
  +function getBorderRadius({size, square}) {
  + if (square) {
  + return size <= 24 ? '4px' : '6px'
  + } else {
  + return '50%'
  }
  }
  @@ -29,7 +23,7 @@ const Avatar = styled.img.attrs(props => ({
  overflow: hidden; // Ensure page layout in Firefox should images fail to load
  line-height: ${get('lineHeights.condensedUltra')};
  vertical-align: middle;
  - ${borderRadius};
  + border-radius: ${props => getBorderRadius(props.size, props.square)};
  ${space};
  `
  @@ -37,7 +31,7 @@ Avatar.defaultProps = {
  theme,
  size: 20,
  alt: '',
  - shape: 'circle'
  + square: false
  }
  Avatar.propTypes = {
  @@ -45,7 +39,7 @@ Avatar.propTypes = {
  size: PropTypes.number,
  src: PropTypes.string,
  ...systemPropTypes.space,
  - shape: PropTypes.PropTypes.oneOf(['square', 'circle']),
  + square: PropTypes.bool,
  theme: PropTypes.object
  }
  