Write blog post about scalafix and scala.meta semantic api

Author: olafurpg

blog/_posts/2017-02-23-scalafix-v0.3.md

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+# Refactor with scalafix
+
+We are happy to announce the release of [scalafix v0.3][scalafix].
+This release introduces a new `Rewrite` and `Patch` API powered by the [scala.meta semantic API][meta-1.6].
+We are excited about this release because we believe it enables a number promising tooling applications.
+
+This first release of the scala.meta semantic API enables rewrites to query for the "symbol" of a name that appears in a Scala source file.
+A symbol is a unique identifier of a definition such as a class, val, def or trait.
+This ability to query for symbols opens possibilities for a great number of refactorings including imports management and identifier renaming.
+To demonstrate what rewrites can be implemented with scalafix v0.3, let's take one example.
+
+## Example: Xor to Either
+
+The functional programming library [cats][cats] migrated recently from its `Xor` data type to `Either` from the standard library.
+It requires a few mechanical steps to migrate code to use `Either` instead of `Xor`.
+For example, below is a diff that's taken from [circe][xor-cire]'s migration to `Either`.
+
+```diff
+-  final def either: Xor[HCursor, HCursor] = if (succeeded) Xor.right(any) else Xor.left(any)
++  final def either: Either[HCursor, HCursor] = if (succeeded) Right(any) else Left(any)
+```
+
+Scalafix rewrites are composed of so-called "patches".
+A patch describes a single refactoring operation.
+`Replace` is one patch that can be used to rename identifiers
+
+```scala
+Replace(Symbol("_root_.cats.data.Xor."), q"Either")
+Replace(Symbol("_root_.cats.data.Xor.Left."), q"Left")
+Replace(Symbol("_root_.cats.data.Xor.Right."), q"Right")
+```
+
+To introduce new imports on renmae, it's possible to pass in `additionalImports`
+```scala
+Replace(Symbol("_root_.cats.data.XorT."), q"EitherT",
+        additionalImports = List(importer"cats.data.EitherT")),
+```
+
+Imports can be removed with the `RemoveGlobalImport` patch
+
+```scala
+RemoveGlobalImport(importer"cats.data.Xor")
+```
+Nothing happens if the import does not appear in the source file.
+Likewise, it's OK to add the same import twice, scalafix will de-duplicate it.
+
+The full `Xor` to `Either` scalafix rewrite can be found [here][xor2either] and its accompanying test
+suite [here][xor2either-test].
+
+To learn more about how to start with scalafix, visit the [installation docs][install]!
+
+## Cross-building
+
+TODO: Shane
+
+## Custom rewrites
+You can write your own custom rewrites.
+
+[xor2either-test]: https://github.com/scalacenter/scalafix/blob/f61136fad79afcdbb03528ce78c7928afc6eafd6/scalafix-nsc/src/test/resources/syntactic/Xor2Either.source
+[xor2either]: https://github.com/scalacenter/scalafix/blob/f61136fad79afcdbb03528ce78c7928afc6eafd6/core/src/main/scala/scalafix/rewrite/Xor2Either.scala
+[xor-circe]: https://github.com/circe/circe/pull/343/files
+[cats]: http://github.com/typelevel/cats
+[ghpages]: http://github.com/scalacenter/scalafix
+[prevpost]: http://scala-lang.org/blog/2016/10/24/scalafix.html
+[scalafix]: https://scalacenter.github.io/scalafix/#0.3.0
+[install]: https://scalacenter.github.io/scalafix/#Installation
+[meta-1.6]: https://github.com/scalameta/scalameta/blob/master/changelog/1.6.0.md#semantic-api