Add support for minification of final output

Hugo Pipes added minification support for resources fetched via ´resources.Get` and similar.

This also adds support for minification of the final output for supported output formats: HTML, XML, SVG, CSS, JavaScript, JSON.

To enable, run Hugo with the `--minify` flag:

```bash
hugo --minify
```

This commit is also a major spring cleaning of the `transform` package to allow the new minification step fit into that processing chain.

Fixes #1251

1 files changed, 36 insertions, 0 deletions

diff --git a/transform/urlreplacers/absurl.go b/transform/urlreplacers/absurl.go
new file mode 100644
index 000000000..029d94da2
--- /dev/null
+++ b/transform/urlreplacers/absurl.go
@@ -0,0 +1,36 @@
+// Copyright 2018 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package urlreplacers
+
+import "github.com/gohugoio/hugo/transform"
+
+var ar = newAbsURLReplacer()
+
+// NewAbsURLTransformer replaces relative URLs with absolute ones
+// in HTML files, using the baseURL setting.
+func NewAbsURLTransformer(path string) transform.Transformer {
+	return func(ft transform.FromTo) error {
+		ar.replaceInHTML(path, ft)
+		return nil
+	}
+}
+
+// NewAbsURLInXMLTransformer replaces relative URLs with absolute ones
+// in XML files, using the baseURL setting.
+func NewAbsURLInXMLTransformer(path string) transform.Transformer {
+	return func(ft transform.FromTo) error {
+		ar.replaceInXML(path, ft)
+		return nil
+	}
+}