feat: use cobra to provide subcommands, move sources to lib (#506)

- Use cobra in order to provide subcommands `serve` and `db`.
  - Subdir `cmd` is removed.
  - Subdir `cli` is created, which is a standard cobra structure.
- Sources related to the core are moved to subdir `lib`.
- #497 and #504 are merged.
- Deprecated flags are added. See https://github.com/filebrowser/filebrowser/pull/497#discussion_r209428120.
- [`viper.BindPFlags`](https://godoc.org/github.com/spf13/viper#BindPFlags) is used in order to reduce the verbosity in `serve.go`.


Former-commit-id: 4b37ad82e91e01f7718cd389469814674bdf7032 [formerly c84d7fcf9c362b2aa1f9e5b57196152f53835e61] [formerly 2fef43c0382f3cc7d13e0297ccb467e38fac6982 [formerly 69a3f853bd2821d2c52a435277aaac68a468d39b]]
Former-commit-id: 2f7dc1b8ee6735382cedae2053f40c546c21de45 [formerly b438417178b47ad5f7caf9cb728f4a5011a09f5e]
Former-commit-id: 07bc58ab2e1ab10c30be8d0a5e760288bfc4d4dc

lib/http/download.go

@@ -0,0 +1,102 @@
+package http
+
+import (
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+	"strings"
+
+	fb "github.com/filebrowser/filebrowser/lib"
+	"github.com/hacdias/fileutils"
+	"github.com/mholt/archiver"
+)
+
+// downloadHandler creates an archive in one of the supported formats (zip, tar,
+// tar.gz or tar.bz2) and sends it to be downloaded.
+func downloadHandler(c *fb.Context, w http.ResponseWriter, r *http.Request) (int, error) {
+	// If the file isn't a directory, serve it using http.ServeFile. We display it
+	// inline if it is requested.
+	if !c.File.IsDir {
+		return downloadFileHandler(c, w, r)
+	}
+
+	query := r.URL.Query().Get("format")
+	files := []string{}
+	names := strings.Split(r.URL.Query().Get("files"), ",")
+
+	// If there are files in the query, sanitize their names.
+	// Otherwise, just append the current path.
+	if len(names) != 0 {
+		for _, name := range names {
+			// Unescape the name.
+			name, err := url.QueryUnescape(name)
+			if err != nil {
+				return http.StatusInternalServerError, err
+			}
+
+			// Clean the slashes.
+			name = fileutils.SlashClean(name)
+			files = append(files, filepath.Join(c.File.Path, name))
+		}
+	} else {
+		files = append(files, c.File.Path)
+	}
+
+	var (
+		extension string
+		ar        archiver.Archiver
+	)
+
+	switch query {
+	// If the format is true, just set it to "zip".
+	case "zip", "true", "":
+		extension, ar = ".zip", archiver.Zip
+	case "tar":
+		extension, ar = ".tar", archiver.Tar
+	case "targz":
+		extension, ar = ".tar.gz", archiver.TarGz
+	case "tarbz2":
+		extension, ar = ".tar.bz2", archiver.TarBz2
+	case "tarxz":
+		extension, ar = ".tar.xz", archiver.TarXZ
+	default:
+		return http.StatusNotImplemented, nil
+	}
+
+	// Defines the file name.
+	name := c.File.Name
+	if name == "." || name == "" {
+		name = "archive"
+	}
+	name += extension
+
+	w.Header().Set("Content-Disposition", "attachment; filename*=utf-8''"+url.PathEscape(name))
+	err := ar.Write(w, files)
+
+	return 0, err
+}
+
+func downloadFileHandler(c *fb.Context, w http.ResponseWriter, r *http.Request) (int, error) {
+	file, err := os.Open(c.File.Path)
+	if err != nil {
+		return http.StatusInternalServerError, err
+	}
+	defer file.Close()
+
+	stat, err := file.Stat()
+	if err != nil {
+		return http.StatusInternalServerError, err
+	}
+
+	if r.URL.Query().Get("inline") == "true" {
+		w.Header().Set("Content-Disposition", "inline")
+	} else {
+		// As per RFC6266 section 4.3
+		w.Header().Set("Content-Disposition", "attachment; filename*=utf-8''"+url.PathEscape(c.File.Name))
+	}
+
+	http.ServeContent(w, r, stat.Name(), stat.ModTime(), file)
+
+	return 0, nil
+}