conf: require sourcedir files to be terminated by newline

When reading a *.sources file require that each line is termined by the
newline character to avoid processing an unfinished line, e.g. due to an
unexpected call of the reload command when the file is being written in
place.

conf.c

@@ -1694,8 +1694,9 @@ load_source_file(const char *filename)
     return;
 
   while (fgets(line, sizeof (line), f)) {
-    if (strlen(line) >= MAX_LINE_LENGTH)
-      continue;
+    /* Require lines to be terminated */
+    if (line[0] == '\0' || line[strlen(line) - 1] != '\n')
+      break;
 
     CPS_NormalizeLine(line);
     if (line[0] == '\0')

doc/chrony.conf.adoc

@@ -2310,7 +2310,8 @@ confdir @SYSCONFDIR@/chrony.d
 [[sourcedir]]*sourcedir* _directory_...::
 The *sourcedir* directive is identical to the *confdir* directive, except the
 configuration files have the _.sources_ suffix, they can only specify NTP
-sources (i.e. use the *server*, *pool*, and *peer* directive), and can be
+sources (i.e. the *server*, *pool*, and *peer* directives), they are expected
+to have all lines terminated by the newline character, and they can be
 reloaded by the <<chronyc.adoc#reload,*reload sources*>> command in
 *chronyc*. It is particularly useful with dynamic sources like NTP servers
 received from a DHCP server, which can be written to a file specific to the