lib: drop support for single-message mbox files

We've supported mbox files containing a single message for historical
reasons, but the support has been deprecated, with a warning message
while indexing, since Notmuch 0.15. Finally drop the support, and
consider all mbox files non-email.

lib/index.cc

@@ -436,8 +436,6 @@ _notmuch_message_index_file (notmuch_message_t *message,
     notmuch_status_t ret = NOTMUCH_STATUS_SUCCESS;
     static int initialized = 0;
     char from_buf[5];
-    bool is_mbox = false;
-    static bool mbox_warning = false;
 
     if (! initialized) {
 	g_mime_init (GMIME_ENABLE_RFC2047_WORKAROUNDS);
@@ -453,36 +451,20 @@ _notmuch_message_index_file (notmuch_message_t *message,
 
     /* Is this mbox? */
     if (fread (from_buf, sizeof (from_buf), 1, file) == 1 &&
-	strncmp (from_buf, "From ", 5) == 0)
+	strncmp (from_buf, "From ", 5) == 0) {
-	is_mbox = true;
+	ret = NOTMUCH_STATUS_FILE_NOT_EMAIL;
+	goto DONE;
+    }
     rewind (file);
 
     /* Evil GMime steals my FILE* here so I won't fclose it. */
     stream = g_mime_stream_file_new (file);
 
     parser = g_mime_parser_new_with_stream (stream);
-    g_mime_parser_set_scan_from (parser, is_mbox);
+    g_mime_parser_set_scan_from (parser, FALSE);
 
     mime_message = g_mime_parser_construct_message (parser);
 
-    if (is_mbox) {
-	if (!g_mime_parser_eos (parser)) {
-	    /* This is a multi-message mbox. */
-	    ret = NOTMUCH_STATUS_FILE_NOT_EMAIL;
-	    goto DONE;
-	}
-	/* For historical reasons, we support single-message mboxes,
-	 * but this behavior is likely to change in the future, so
-	 * warn. */
-	if (!mbox_warning) {
-	    mbox_warning = true;
-	    fprintf (stderr, "\
-Warning: %s is an mbox containing a single message,\n\
-likely caused by misconfigured mail delivery.  Support for single-message\n\
-mboxes is deprecated and may be removed in the future.\n", filename);
-	}
-    }
-
     from = g_mime_message_get_sender (mime_message);
 
     addresses = internet_address_list_parse_string (from);

test/T050-new.sh

@@ -163,22 +163,6 @@ rm -rf "${MAIL_DIR}"/two
 output=$(NOTMUCH_NEW)
 test_expect_equal "$output" "No new mail. Removed 3 messages."
 
-test_begin_subtest "Support single-message mbox (deprecated)"
-cat > "${MAIL_DIR}"/mbox_file1 <<EOF
-From test_suite@notmuchmail.org Fri Jan  5 15:43:57 2001
-From: Notmuch Test Suite <test_suite@notmuchmail.org>
-To: Notmuch Test Suite <test_suite@notmuchmail.org>
-Subject: Test mbox message 1
-
-Body.
-EOF
-output=$(NOTMUCH_NEW 2>&1)
-test_expect_equal "$output" \
-"Warning: ${MAIL_DIR}/mbox_file1 is an mbox containing a single message,
-likely caused by misconfigured mail delivery.  Support for single-message
-mboxes is deprecated and may be removed in the future.
-Added 1 new message to the database."
-
 # This test requires that notmuch new has been run at least once.
 test_begin_subtest "Skip and report non-mail files"
 generate_message
@@ -200,14 +184,24 @@ Subject: Test mbox message 2
 
 Body 2.
 EOF
+cat > "${MAIL_DIR}"/mbox_file1 <<EOF
+From test_suite@notmuchmail.org Fri Jan  5 15:43:57 2001
+From: Notmuch Test Suite <test_suite@notmuchmail.org>
+To: Notmuch Test Suite <test_suite@notmuchmail.org>
+Subject: Test mbox message 1
+
+Body.
+EOF
 output=$(NOTMUCH_NEW 2>&1)
 test_expect_equal "$output" \
 "Note: Ignoring non-mail file: ${MAIL_DIR}/.git/config
 Note: Ignoring non-mail file: ${MAIL_DIR}/.ignored_hidden_file
 Note: Ignoring non-mail file: ${MAIL_DIR}/ignored_file
 Note: Ignoring non-mail file: ${MAIL_DIR}/mbox_file
+Note: Ignoring non-mail file: ${MAIL_DIR}/mbox_file1
 Added 1 new message to the database."
 rm "${MAIL_DIR}"/mbox_file
+rm "${MAIL_DIR}"/mbox_file1
 
 test_begin_subtest "Ignore files and directories specified in new.ignore"
 generate_message