render_hkl: Update docs

doc/man/render_hkl.1

@@ -32,6 +32,13 @@ Specify the indices for the downward direction of the resulting plot.  Default:
 .PD
 Specify the indices for the 'right' direction of the resulting plot.  The direction will be approximately to the right, the exact direction depending on the unit cell.  Default: \fB--right=0,1,0\fR.
 
+.PD 0
+.IP "\fB--zone=\fR\fIz\fR
+.PD
+Show reflections for which \fBg\fR.\fBr\fR=\fIz\fR, where \fBg\fR is the
+reflection index (i.e. hkl) and \fBr\fR is the zone axis direction.  \fIz\fR
+hence represents the Laue zone number.
+
 .PD 0
 .IP "\fB-o\fR \fIfilename\fR"
 .IP \fB--output=\fR\fIfilename\fR

src/render_hkl.c

@@ -64,6 +64,7 @@ static void show_help(const char *s)
 "                           Default: 1,0,0.\n"
 "  -r, --right=<h>,<k>,<l> Indices for the axis in the 'right' (roughly)\n"
 "                           direction.  Default: 0,1,0.\n"
+"      --zone=<z>          Show the <z>th Laue zone.\n"
 "  -o, --output=<filename> Output filename.  Default: za.pdf\n"
 "      --boost=<val>       Squash colour scale by <val>.\n"
 "  -p, --pdb=<file>        PDB file from which to get the unit cell.\n"
@@ -79,8 +80,9 @@ static void show_help(const char *s)
 "                           according to:\n"
 "                            I      : the intensity of the reflection.\n"
 "                            sqrtI  : the square root of the intensity.\n"
-"                            count  : the number of measurements for the reflection.\n"
-"                                     (after correcting for 'epsilon')\n"
+"                            count  : the number of measurements for the\n"
+"                                     reflection (after correcting for\n"
+"                                     multiplicity 'epsilon').\n"
 "                            rawcts : the raw number of measurements for the\n"
 "                                     reflection (no 'epsilon' correction).\n"
 "\n"