Add unreachable options to manpage (#14164)

man/crystal.1

@@ -411,9 +411,49 @@ to specify the cursor position. The format for the cursor position is file:line:
 .It Cm types
 Show type of main variables of file.
 .It Cm unreachable
-Show methods that are never called. The output is a list of lines with columns
-separated by tab. The first column is the location of the def, the second column
-its reference name and the third column is the length in lines.
+Show methods that are never called. The text output is a list of lines with columns
+separated by tab.
+
+.Pp
+Output fields:
+
+.Bl -tag -width "1234567890" -compact
+.Pp
+.It Cm count
+sum of all calls to this method (only with
+.Fl -tallies
+ option; otherwise skipped)
+.It Cm location
+pathname, line and column, all separated by colon
+.It Cm name
+.It Cm lines
+length of the def in lines
+.It Cm annotations
+.El
+
+.Pp
+Options:
+.Bl -tag -width "12345678" -compact
+.Pp
+.It Fl D Ar FLAG, Fl -define= Ar FLAG
+Define a compile-time flag. This is useful to conditionally define types, methods, or commands based on flags available at compile time. The default flags are from the target triple given with --target-triple or the hosts default, if none is given.
+.It Fl f Ar FORMAT, Fl -format= Ar FORMAT
+Output format 'text' (default), 'json', or 'csv'.
+.It Fl -tallies
+Print reachable methods and their call counts as well.
+.It Fl -check
+Exit with error if there is any unreachable code.
+.It Fl i Ar PATH, Fl -include= Ar PATH
+Include path in output.
+.It Fl e Ar PATH, Fl -exclude= Ar PATH
+Exclude path in output (default:
+.Sy lib
+).
+.It Fl -error-trace
+Show full error trace.
+.It Fl -prelude
+Specify prelude to use. The default one initializes the garbage collector. You can also use --prelude=empty to use no preludes. This can be useful for checking code generation for a specific source code file.
+.El
 .El
 .Pp
 .It