local: add --skip-specials to ignore special files

Give users a way to explicitly acknowledge that pipes, sockets and block
devices are to be ignored without warnings.

This follows the precedent set in commit 6152bab28 (local: add
--skip-links to suppress symlink warnings, 2017-07-21) for ignoring
warnings about symlinks.

backend/local/local.go

@@ -117,6 +117,17 @@ points, as you explicitly acknowledge that they should be skipped.`,
 				NoPrefix: true,
 				Advanced: true,
 			},
+			{
+				Name: "skip_specials",
+				Help: `Don't warn about skipped pipes, sockets and device objects.
+
+This flag disables warning messages on skipped pipes, sockets and
+device objects, as you explicitly acknowledge that they should be
+skipped.`,
+				Default:  false,
+				NoPrefix: true,
+				Advanced: true,
+			},
 			{
 				Name: "zero_size_links",
 				Help: `Assume the Stat size of links is zero (and read them instead) (deprecated).
@@ -324,6 +335,7 @@ type Options struct {
 	FollowSymlinks    bool                 `config:"copy_links"`
 	TranslateSymlinks bool                 `config:"links"`
 	SkipSymlinks      bool                 `config:"skip_links"`
+	SkipSpecials      bool                 `config:"skip_specials"`
 	UTFNorm           bool                 `config:"unicode_normalization"`
 	NoCheckUpdated    bool                 `config:"no_check_updated"`
 	NoUNC             bool                 `config:"nounc"`
@@ -1201,7 +1213,9 @@ func (o *Object) Storable() bool {
 		}
 		return false
 	} else if mode&(os.ModeNamedPipe|os.ModeSocket|os.ModeDevice) != 0 {
-		fs.Logf(o, "Can't transfer non file/directory")
+		if !o.fs.opt.SkipSpecials {
+			fs.Logf(o, "Can't transfer non file/directory")
+		}
 		return false
 	} else if mode&os.ModeDir != 0 {
 		// fs.Debugf(o, "Skipping directory")

docs/content/commands/rclone.md

@@ -834,6 +834,7 @@ rclone [flags]
       --sia-user-agent string                               Siad User Agent (default "Sia-Agent")
       --size-only                                           Skip based on size only, not modtime or checksum
       --skip-links                                          Don't warn about skipped symlinks
+      --skip-specials                                       Don't warn about skipped pipes, sockets and device objects
       --smb-case-insensitive                                Whether the server is configured to be case-insensitive (default true)
       --smb-description string                              Description of the remote
       --smb-domain string                                   Domain name for NTLM authentication (default "WORKGROUP")

docs/content/flags.md

@@ -975,6 +975,7 @@ Backend-only flags (these can be set in the config file also).
       --sia-encoding Encoding                               The encoding for the backend (default Slash,Question,Hash,Percent,Del,Ctl,InvalidUtf8,Dot)
       --sia-user-agent string                               Siad User Agent (default "Sia-Agent")
       --skip-links                                          Don't warn about skipped symlinks
+      --skip-specials                                       Don't warn about skipped pipes, sockets and device objects
       --smb-case-insensitive                                Whether the server is configured to be case-insensitive (default true)
       --smb-description string                              Description of the remote
       --smb-domain string                                   Domain name for NTLM authentication (default "WORKGROUP")

docs/content/local.md

@@ -386,6 +386,21 @@ Properties:
 - Type:        bool
 - Default:     false
 
+#### --skip-specials
+
+Don't warn about skipped pipes, sockets and device objects.
+
+This flag disables warning messages on skipped pipes, sockets and
+device objects, as you explicitly acknowledge that they should be
+skipped.`,
+
+Properties:
+
+- Config:      skip_specials
+- Env Var:     RCLONE_LOCAL_SKIP_SPECIALS
+- Type:        bool
+- Default:     false
+
 #### --local-zero-size-links
 
 Assume the Stat size of links is zero (and read them instead) (deprecated).