Use standard lessc and minify CSS using Node.js

This changes the previous nonstandard `lessc` to the official one and
enables CSS minification via the clean-css module.

To build CSS, Node.js is required along with a `npm install` to get the
tools installed locally in node_modules so there is no dependency on
binaries in PATH. Benefits include:

- Allows one to have a standard lessc in PATH.
- Can now use command line switches on lessc.
- Minified CSS brings faster page load times and also has the benefit
  of discouraging contributors from editing CSS directly.

To build CSS, Node.js is required along with a `npm install` to get the
tools installed locally based on the information in `package.json`.

The 'make stylesheet' task was modified to run without condition. This
makes it easier to work on the make task itself without having to delete
files.

Also fixes: go-gitea#2198

.gitignore

@@ -58,3 +58,4 @@ coverage.all
 /integrations/indexers-sqlite
 /integrations/mysql.ini
 /integrations/pgsql.ini
+/node_modules

CONTRIBUTING.md

@@ -97,6 +97,16 @@ and is synced regularily to Crowdin. Once a translation has reached
 A SATISFACTORY PERCENTAGE it will be synced back into this repo and
 included in the next released version.
 
+## Building Gitea
+
+Generally, the go build tools are installed as-needed in the `Makefile`.
+An exception are the tools to build the CSS and images.
+
+- To build CSS: Install [Node.js](https://nodejs.org/en/download/package-manager)
+  with `npm` and then run `npm install` and `make stylesheets`.
+- To build Images: ImageMagick, inkscape and zopflipng binaries must be
+  available in your `PATH` to run `make generate-images`.
+
 ## Code review
 
 Changes to Gitea must be reviewed before they are accepted, no matter who

Makefile

@@ -15,7 +15,6 @@ else
 endif
 
 BINDATA := modules/{options,public,templates}/bindata.go
-STYLESHEETS := $(wildcard public/less/index.less public/less/_*.less)
 DOCKER_TAG := gitea/gitea:latest
 GOFILES := $(shell find . -name "*.go" -type f ! -path "./vendor/*" ! -path "*/bindata.go")
 GOFMT ?= gofmt -s
@@ -298,15 +297,9 @@ stylesheets-check: stylesheets
 		exit 1; \
 	fi;
 
-.PHONY: stylesheets
-stylesheets: public/css/index.css
-
-.IGNORE: public/css/index.css
-public/css/index.css: $(STYLESHEETS)
-	@which lessc > /dev/null; if [ $$? -ne 0 ]; then \
-		$(GO) get -u github.com/kib357/less-go/lessc; \
-	fi
-	lessc -i $< -o $@
+stylesheets:
+	node_modules/.bin/lessc --no-ie-compat public/less/index.less public/css/index.css
+	node_modules/.bin/cleancss -o public/css/index.css public/css/index.css
 
 .PHONY: swagger-ui
 swagger-ui:

package.json

@@ -0,0 +1,7 @@
+{
+  "license": "MIT",
+  "dependencies": {
+    "clean-css-cli": "^4.1.6",
+    "less": "^2.7.2"
+  }
+}