Index: node_modules/postcss/lib/previous-map.js
===================================================================
--- node_modules/postcss/lib/previous-map.js	(revision 2058e5c694bb6097866a5fe6503c519e8f74970f)
+++ node_modules/postcss/lib/previous-map.js	(revision 2058e5c694bb6097866a5fe6503c519e8f74970f)
@@ -0,0 +1,144 @@
+'use strict'
+
+let { existsSync, readFileSync } = require('fs')
+let { dirname, join } = require('path')
+let { SourceMapConsumer, SourceMapGenerator } = require('source-map-js')
+
+function fromBase64(str) {
+  if (Buffer) {
+    return Buffer.from(str, 'base64').toString()
+  } else {
+    /* c8 ignore next 2 */
+    return window.atob(str)
+  }
+}
+
+class PreviousMap {
+  constructor(css, opts) {
+    if (opts.map === false) return
+    this.loadAnnotation(css)
+    this.inline = this.startWith(this.annotation, 'data:')
+
+    let prev = opts.map ? opts.map.prev : undefined
+    let text = this.loadMap(opts.from, prev)
+    if (!this.mapFile && opts.from) {
+      this.mapFile = opts.from
+    }
+    if (this.mapFile) this.root = dirname(this.mapFile)
+    if (text) this.text = text
+  }
+
+  consumer() {
+    if (!this.consumerCache) {
+      this.consumerCache = new SourceMapConsumer(this.text)
+    }
+    return this.consumerCache
+  }
+
+  decodeInline(text) {
+    let baseCharsetUri = /^data:application\/json;charset=utf-?8;base64,/
+    let baseUri = /^data:application\/json;base64,/
+    let charsetUri = /^data:application\/json;charset=utf-?8,/
+    let uri = /^data:application\/json,/
+
+    let uriMatch = text.match(charsetUri) || text.match(uri)
+    if (uriMatch) {
+      return decodeURIComponent(text.substr(uriMatch[0].length))
+    }
+
+    let baseUriMatch = text.match(baseCharsetUri) || text.match(baseUri)
+    if (baseUriMatch) {
+      return fromBase64(text.substr(baseUriMatch[0].length))
+    }
+
+    let encoding = text.match(/data:application\/json;([^,]+),/)[1]
+    throw new Error('Unsupported source map encoding ' + encoding)
+  }
+
+  getAnnotationURL(sourceMapString) {
+    return sourceMapString.replace(/^\/\*\s*# sourceMappingURL=/, '').trim()
+  }
+
+  isMap(map) {
+    if (typeof map !== 'object') return false
+    return (
+      typeof map.mappings === 'string' ||
+      typeof map._mappings === 'string' ||
+      Array.isArray(map.sections)
+    )
+  }
+
+  loadAnnotation(css) {
+    let comments = css.match(/\/\*\s*# sourceMappingURL=/g)
+    if (!comments) return
+
+    // sourceMappingURLs from comments, strings, etc.
+    let start = css.lastIndexOf(comments.pop())
+    let end = css.indexOf('*/', start)
+
+    if (start > -1 && end > -1) {
+      // Locate the last sourceMappingURL to avoid pickin
+      this.annotation = this.getAnnotationURL(css.substring(start, end))
+    }
+  }
+
+  loadFile(path) {
+    this.root = dirname(path)
+    if (existsSync(path)) {
+      this.mapFile = path
+      return readFileSync(path, 'utf-8').toString().trim()
+    }
+  }
+
+  loadMap(file, prev) {
+    if (prev === false) return false
+
+    if (prev) {
+      if (typeof prev === 'string') {
+        return prev
+      } else if (typeof prev === 'function') {
+        let prevPath = prev(file)
+        if (prevPath) {
+          let map = this.loadFile(prevPath)
+          if (!map) {
+            throw new Error(
+              'Unable to load previous source map: ' + prevPath.toString()
+            )
+          }
+          return map
+        }
+      } else if (prev instanceof SourceMapConsumer) {
+        return SourceMapGenerator.fromSourceMap(prev).toString()
+      } else if (prev instanceof SourceMapGenerator) {
+        return prev.toString()
+      } else if (this.isMap(prev)) {
+        return JSON.stringify(prev)
+      } else {
+        throw new Error(
+          'Unsupported previous source map format: ' + prev.toString()
+        )
+      }
+    } else if (this.inline) {
+      return this.decodeInline(this.annotation)
+    } else if (this.annotation) {
+      let map = this.annotation
+      if (file) map = join(dirname(file), map)
+      return this.loadFile(map)
+    }
+  }
+
+  startWith(string, start) {
+    if (!string) return false
+    return string.substr(0, start.length) === start
+  }
+
+  withContent() {
+    return !!(
+      this.consumer().sourcesContent &&
+      this.consumer().sourcesContent.length > 0
+    )
+  }
+}
+
+module.exports = PreviousMap
+PreviousMap.default = PreviousMap