Extract providers to their own package

This is just doing that and making it compile :)

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

provider/file/file.go

@@ -0,0 +1,85 @@
+package file
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/BurntSushi/toml"
+	"github.com/containous/traefik/log"
+	"github.com/containous/traefik/provider"
+	"github.com/containous/traefik/safe"
+	"github.com/containous/traefik/types"
+	"gopkg.in/fsnotify.v1"
+)
+
+var _ provider.Provider = (*Provider)(nil)
+
+// Provider holds configurations of the provider.
+type Provider struct {
+	provider.BaseProvider `mapstructure:",squash"`
+}
+
+// Provide allows the file provider to provide configurations to traefik
+// using the given configuration channel.
+func (p *Provider) Provide(configurationChan chan<- types.ConfigMessage, pool *safe.Pool, constraints types.Constraints) error {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		log.Error("Error creating file watcher", err)
+		return err
+	}
+
+	file, err := os.Open(p.Filename)
+	if err != nil {
+		log.Error("Error opening file", err)
+		return err
+	}
+	defer file.Close()
+
+	if p.Watch {
+		// Process events
+		pool.Go(func(stop chan bool) {
+			defer watcher.Close()
+			for {
+				select {
+				case <-stop:
+					return
+				case event := <-watcher.Events:
+					if strings.Contains(event.Name, file.Name()) {
+						log.Debug("Provider event:", event)
+						configuration := p.loadFileConfig(file.Name())
+						if configuration != nil {
+							configurationChan <- types.ConfigMessage{
+								ProviderName:  "file",
+								Configuration: configuration,
+							}
+						}
+					}
+				case error := <-watcher.Errors:
+					log.Error("Watcher event error", error)
+				}
+			}
+		})
+		err = watcher.Add(filepath.Dir(file.Name()))
+		if err != nil {
+			log.Error("Error adding file watcher", err)
+			return err
+		}
+	}
+
+	configuration := p.loadFileConfig(file.Name())
+	configurationChan <- types.ConfigMessage{
+		ProviderName:  "file",
+		Configuration: configuration,
+	}
+	return nil
+}
+
+func (p *Provider) loadFileConfig(filename string) *types.Configuration {
+	configuration := new(types.Configuration)
+	if _, err := toml.DecodeFile(filename, configuration); err != nil {
+		log.Error("Error reading file:", err)
+		return nil
+	}
+	return configuration
+}