update

node_modules/postcss/docs/source-maps.md

@@ -0,0 +1,74 @@
+# PostCSS and Source Maps
+
+PostCSS has great [source maps] support. It can read and interpret maps
+from previous transformation steps, autodetect the format that you expect,
+and output both external and inline maps.
+
+To ensure that you generate an accurate source map, you must indicate the input
+and output CSS file paths — using the options `from` and `to`, respectively.
+
+To generate a new source map with the default options, simply set `map: true`.
+This will generate an inline source map that contains the source content.
+If you don’t want the map inlined, you can set `map.inline: false`.
+
+```js
+processor
+  .process(css, {
+    from: 'app.sass.css',
+    to:   'app.css',
+    map: { inline: false }
+  })
+  .then(result => {
+      result.map //=> '{ "version":3,
+                 //      "file":"app.css",
+                 //      "sources":["app.sass"],
+                 //       "mappings":"AAAA,KAAI" }'
+  })
+```
+
+If PostCSS finds source maps from a previous transformation,
+it will automatically update that source map with the same options.
+
+## Options
+
+If you want more control over source map generation, you can define the `map`
+option as an object with the following parameters:
+
+* `inline` boolean: indicates that the source map should be embedded
+  in the output CSS as a Base64-encoded comment. By default, it is `true`.
+  But if all previous maps are external, not inline, PostCSS will not embed
+  the map even if you do not set this option.
+
+  If you have an inline source map, the `result.map` property will be empty,
+  as the source map will be contained within the text of `result.css`.
+
+* `prev` string, object, boolean or function: source map content from
+  a previous processing step (for example, Sass compilation).
+  PostCSS will try to read the previous source map automatically
+  (based on comments within the source CSS), but you can use this option
+  to identify it manually. If desired, you can omit the previous map
+  with `prev: false`.
+
+* `sourcesContent` boolean: indicates that PostCSS should set the origin
+  content (for example, Sass source) of the source map. By default,
+  it is `true`. But if all previous maps do not contain sources content,
+  PostCSS will also leave it out even if you do not set this option.
+
+* `annotation` boolean or string: indicates that PostCSS should add annotation
+  comments to the CSS. By default, PostCSS will always add a comment with a path
+  to the source map. PostCSS will not add annotations to CSS files that
+  do not contain any comments.
+
+  By default, PostCSS presumes that you want to save the source map as
+  `opts.to + '.map'` and will use this path in the annotation comment.
+  A different path can be set by providing a string value for `annotation`.
+
+  If you have set `inline: true`, annotation cannot be disabled.
+
+* `from` string: by default, PostCSS will set the `sources` property of the map
+  to the value of the `from` option. If you want to override this behaviour, you
+  can use `map.from` to explicitly set the source map's `sources` property.
+  Path should be absolute or relative from generated file
+  (`to` option in `process()` method).
+
+[source maps]: http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/