fs: allow setting of --http_proxy from command line

This in turn allows `override.http_proxy` to be set in backend configs
to set an http proxy for a single backend.

docs/content/docs.md

@@ -1384,6 +1384,15 @@ rclone sync --interactive ~/src s3:test/dst --header-upload "Content-Disposition
 See GitHub issue [#59](https://github.com/rclone/rclone/issues/59) for
 currently supported backends.
 
+### --http-proxy string
+
+Use this option to set an HTTP proxy for all HTTP based services to
+use.
+
+Rclone also supports the standard HTTP proxy environment variables
+which it will pick up automatically. The is the way the HTTP proxy
+will normally be set but this flag can be used to override it.
+
 ### --human-readable
 
 Rclone commands output values for sizes (e.g. number of bytes) and

docs/content/faq.md

@@ -148,6 +148,16 @@ export NO_PROXY=$no_proxy
 
 Note that the FTP backend does not support `ftp_proxy` yet.
 
+You can use the command line argument `--http-proxy` to set the proxy,
+and in turn use an override in the config file if you want it set for
+a single backend, eg `override.http_proxy = http://...` in the config
+file.
+
+The FTP and SFTP backends have their own `http_proxy` settings to
+support an HTTP CONNECT proxy (
+[--ftp-http-proxy](https://rclone.org/ftp/#ftp-http-proxy) and
+[--sftp-http-proxy](https://rclone.org/ftp/#sftp-http-proxy) )
+
 ### Rclone gives x509: failed to load system roots and no roots provided error
 
 This means that `rclone` can't find the SSL root certificates.  Likely

fs/config.go

@@ -555,6 +555,11 @@ var ConfigOptionsInfo = Options{{
 	Default: []string{},
 	Help:    "Transform paths during the copy process.",
 	Groups:  "Copy",
+}, {
+	Name:    "http_proxy",
+	Default: "",
+	Help:    "HTTP proxy URL.",
+	Groups:  "Networking",
 }}
 
 // ConfigInfo is filesystem config options
@@ -667,6 +672,7 @@ type ConfigInfo struct {
 	MetadataMapper             SpaceSepList      `config:"metadata_mapper"`
 	MaxConnections             int               `config:"max_connections"`
 	NameTransform              []string          `config:"name_transform"`
+	HTTPProxy                  string            `config:"http_proxy"`
 }
 
 func init() {

fs/fshttp/http.go

@@ -6,10 +6,12 @@ import (
 	"context"
 	"crypto/tls"
 	"crypto/x509"
+	"fmt"
 	"net"
 	"net/http"
 	"net/http/cookiejar"
 	"net/http/httputil"
+	"net/url"
 	"os"
 	"sync"
 	"time"
@@ -55,7 +57,18 @@ func NewTransportCustom(ctx context.Context, customize func(*http.Transport)) ht
 	// This also means we get new stuff when it gets added to go
 	t := new(http.Transport)
 	structs.SetDefaults(t, http.DefaultTransport.(*http.Transport))
-	t.Proxy = http.ProxyFromEnvironment
+	if ci.HTTPProxy != "" {
+		proxyURL, err := url.Parse(ci.HTTPProxy)
+		if err != nil {
+			t.Proxy = func(*http.Request) (*url.URL, error) {
+				return nil, fmt.Errorf("failed to set --http-proxy from %q: %w", ci.HTTPProxy, err)
+			}
+		} else {
+			t.Proxy = http.ProxyURL(proxyURL)
+		}
+	} else {
+		t.Proxy = http.ProxyFromEnvironment
+	}
 	t.MaxIdleConnsPerHost = 2 * (ci.Checkers + ci.Transfers + 1)
 	t.MaxIdleConns = 2 * t.MaxIdleConnsPerHost
 	t.TLSHandshakeTimeout = time.Duration(ci.ConnectTimeout)