doc: make -f Makefile.doc (#2919)

mechanical change: create the manual pages.

Signed-off-by: Miek Gieben <miek@miek.nl>

man/coredns-file.7

@@ -1,5 +1,5 @@
 .\" Generated by Mmark Markdown Processer - mmark.nl
-.TH "COREDNS-FILE" 7 "April 2019" "CoreDNS" "CoreDNS Plugins"
+.TH "COREDNS-FILE" 7 "June 2019" "CoreDNS" "CoreDNS Plugins"
 
 .SH "NAME"
 .PP
@@ -50,7 +50,7 @@ file DBFILE [ZONES... ] {
 \fB\fCtransfer\fR enables zone transfers. It may be specified multiples times. \fB\fCTo\fR or \fB\fCfrom\fR signals
 the direction. \fBADDRESS\fP must be denoted in CIDR notation (e.g., 127.0.0.1/32) or just as plain
 addresses. The special wildcard \fB\fC*\fR means: the entire internet (only valid for 'transfer to').
-When an address is specified a notify message will be send whenever the zone is reloaded.
+When an address is specified a notify message will be sent whenever the zone is reloaded.
 .IP \(bu 4
 \fB\fCreload\fR interval to perform a reload of the zone if the SOA version changes. Default is one minute.
 Value of \fB\fC0\fR means to not scan for changes and reload. For example, \fB\fC30s\fR checks the zonefile every 30 seconds
@@ -97,3 +97,49 @@ Or use a single zone file for multiple zones:
 .fi
 .RE
 
+.PP
+Note that if you have a configuration like the following you may run into a problem of the origin
+not being correctly recognized:
+
+.PP
+.RS
+
+.nf
+\&. {
+    file db.example.org
+}
+
+.fi
+.RE
+
+.PP
+We omit the origin for the file \fB\fCdb.example.org\fR, so this references the zone in the server block,
+which, in this case, is the root zone. Any contents of \fB\fCdb.example.org\fR will then read with that
+origin set; this may or may not do what you want.
+It's better to be explicit here and specify the correct origin. This can be done in two ways:
+
+.PP
+.RS
+
+.nf
+\&. {
+    file db.example.org example.org
+}
+
+.fi
+.RE
+
+.PP
+Or
+
+.PP
+.RS
+
+.nf
+example.org {
+    file db.example.org
+}
+
+.fi
+.RE
+