mail: new option --skip-empty-attachments

* libmailutils/cli/cli.c (mu_cli): Use "no-" prefix to indicate negation
* mail/mail.c (skip_empty_attachments): New global.
(mail_options): New option --skip-empty-attachments
* mail/mail.h (skip_empty_attachments): New extern.
* mail/send.c (atchinfo) <skip_empty>: New field.
(send_attach_file): Initialize skip_empty
(saveatt): Optionally skip empty attachments

* NEWS: Mention the new option.
* doc/texinfo/programs.texi: Document the new option.

-GNU mailutils NEWS -- history of user-visible changes. 2017-01-13
+GNU mailutils NEWS -- history of user-visible changes. 2017-01-16
 Copyright (C) 2002-2017 Free Software Foundation, Inc.
 See the end of file for copying conditions.
 
@@ -40,6 +40,9 @@ obvious reasons, the interactive mode is suppressed in this case.
 The `--attach-fd' option is useful when calling `mail' from another
 program.
 
+The new option `--skip-empty-attachments' instructs `mail' to omit
+attachments that have zero-size body.
+
 Example:
 
 Suppose that the 'mail' binary is opened at file descriptor 5 and

@@ -3044,6 +3044,13 @@ Cause interrupts to terminate program.
 Sets the return email address for outgoing mail.
 @xref{return-address}.
 
+@item --skip-empty-attachments
+@itemx --no-skip-empty-attachments
+Don't create attachments that would have zero-size body.  This
+option affects all attachments created by @option{--attach} and
+@option{--attach-fd} options appearing after it in the command line.
+To cancel its effect, use the @option{--no-skip-empty-attachments} option.
+
 @item -s @var{subj}
 @itemx --subject=@var{subj}
 Send a message with a Subject of @var{subj}.  Valid only in sending
@@ -3531,6 +3538,12 @@ Attachments created with this option have neither filename nor
 description set, so normally the use of @option{--content-name} and/or
 @option{--content-filename} is advised.
 
+The option @option{--skip-empty-attachments} instructs @command{mail}
+to skip creating attachments that would have zero-size body.  This
+option affects all attachments created by @option{--attach} and
+@option{--attach-fd} options appearing after it in the command line.
+To cancel its effect, use the @option{--no-skip-empty-attachments} option.
+
 The following Perl program serves as an example of using
 @command{mail} from a script to construct a MIME message on the fly.
 It scans all mounted file systems for executable files that have

@@ -710,6 +710,9 @@ mu_cli (int argc, char **argv, struct mu_cli_setup *setup, char **capa,
   pohint.po_version_hook = mu_version_hook;
   pohint.po_flags |= MU_PARSEOPT_VERSION_HOOK;
 
+  pohint.po_negation = "no-";
+  pohint.po_flags |= MU_PARSEOPT_NEGATION;
+  
   cfhint.site_file = mu_site_config_file ();
   cfhint.flags = MU_CFHINT_SITE_FILE | MU_CFHINT_PER_USER_FILE;
   

@@ -36,10 +36,11 @@ int hint;
 char *file;
 char *user;
 
+int skip_empty_attachments;
 char *default_encoding;
 char *default_content_type;
-char *content_name;
-char *content_filename;
+static char *content_name;
+static char *content_filename;
 
 static void
 cli_f_option (struct mu_parseopt *po, struct mu_option *opt, char const *arg)
@@ -108,14 +109,12 @@ cli_command_option (struct mu_parseopt *po, struct mu_option *opt,
       break;
 
     case 0:
-      mu_parseopt_error (po,
-			 _("--%s: option should have been recognized"),
+      mu_parseopt_error (po, _("--%s: option should have been recognized"),
 			 opt->opt_long);
       exit (po->po_exit_error);
       
     default:
-      mu_parseopt_error (po,
-			 _("-%c: option should have been recognized"),
+      mu_parseopt_error (po, _("-%c: option should have been recognized"),
 			 opt->opt_short);
       exit (po->po_exit_error);
     }      
@@ -240,6 +239,10 @@ static struct mu_option mail_options[] = {
   { "append",   'a', N_("HEADER: VALUE"), MU_OPTION_DEFAULT,
     N_("append given header to the message being sent"),
     mu_c_string, NULL, cli_append },
+
+  { "skip-empty-attachments", 0, NULL, MU_OPTION_DEFAULT,
+    N_("skip attachments with empty body"),
+    mu_c_bool, &skip_empty_attachments },
     
   { "exec" ,    'E', N_("COMMAND"), MU_OPTION_DEFAULT,
     N_("execute COMMAND"),

@@ -173,7 +173,8 @@ extern int interactive;
 extern const char *program_version;
 extern char *default_encoding;
 extern char *default_content_type;
-
+extern int skip_empty_attachments;
+  
 /* Functions */
 extern int mail_alias (int argc, char **argv);
 extern int mail_alt (int argc, char **argv);	/* command alternates */

@@ -140,6 +140,7 @@ struct atchinfo
   char *name;
   char *filename;
   mu_stream_t source;
+  int skip_empty;
 };
 
 static mu_list_t attlist;
@@ -256,6 +257,7 @@ send_attach_file (int fd,
   aptr->name = content_name ? mu_strdup (content_name) : NULL;
   aptr->filename = content_filename ? mu_strdup (content_filename) : NULL;
   aptr->source = stream;
+  aptr->skip_empty = skip_empty_attachments;
   rc = mu_list_append (attlist, aptr);
   if (rc)
     {
@@ -363,11 +365,31 @@ saveatt (void *item, void *data)
   rc = mu_attachment_copy_from_stream (part, aptr->source, aptr->encoding);
   if (rc)
     {
-      mu_error (_("cannot attach %s: %s"), aptr->filename,
-		mu_strerror (rc));
+      mu_error (_("cannot attach %s: %s"), aptr->id, mu_strerror (rc));
       return 1;
     }
 
+  if (aptr->skip_empty)
+    {
+      mu_body_t body;
+      size_t size;
+      
+      rc = mu_message_get_body (part, &body);
+      if (rc)
+	{
+	  mu_diag_funcall (MU_DIAG_ERROR, "mu_message_get_body", aptr->id, rc);
+	  return 1;
+	}
+      rc = mu_body_size (body, &size);
+      if (rc)
+	{
+	  mu_diag_funcall (MU_DIAG_ERROR, "mu_body_size", aptr->id, rc);
+	  return 1;
+	}
+      if (size == 0)
+	return 0;
+    }
+      
   mu_mime_get_num_parts	(mime, &nparts);
   mu_message_get_header (part, &hdr);
   mu_rfc2822_msg_id (nparts, &p);