decimal: fix godoc

The patch fixes markdown of Decimal.UnmarshalMsgpack method in godoc. It
also makes the package description less confusing, removes duplication.

Closes #201

Author: oleg-jukovec

decimal/bcd.go

@@ -1,45 +1,3 @@
-// Package decimal implements methods to encode and decode BCD.
-//
-// BCD (Binary-Coded Decimal) is a sequence of bytes representing decimal
-// digits of the encoded number (each byte has two decimal digits each encoded
-// using 4-bit nibbles), so byte >> 4 is the first digit and byte & 0x0f is the
-// second digit. The leftmost digit in the array is the most significant. The
-// rightmost digit in the array is the least significant.
-//
-// The first byte of the BCD array contains the first digit of the number,
-// represented as follows:
-//
-//     |  4 bits           |  4 bits           |
-//        = 0x                = the 1st digit
-//
-// (The first nibble contains 0 if the decimal number has an even number of
-// digits). The last byte of the BCD array contains the last digit of the
-// number and the final nibble, represented as follows:
-//
-//     |  4 bits           |  4 bits           |
-//        = the last digit    = nibble
-//
-// The final nibble represents the number's sign: 0x0a, 0x0c, 0x0e, 0x0f stand
-// for plus, 0x0b and 0x0d stand for minus.
-//
-// Examples:
-//
-// The decimal -12.34 will be encoded as 0xd6, 0x01, 0x02, 0x01, 0x23, 0x4d:
-//
-// | MP_EXT (fixext 4) | MP_DECIMAL | scale |  1   |  2,3 |  4 (minus) |
-// |        0xd6       |    0x01    | 0x02  | 0x01 | 0x23 | 0x4d       |
-//
-// The decimal 0.000000000000000000000000000000000010 will be encoded as
-// 0xc7, 0x03, 0x01, 0x24, 0x01, 0x0c:
-//
-// | MP_EXT (ext 8) | length | MP_DECIMAL | scale |  1   | 0 (plus) |
-// |      0xc7      |  0x03  |    0x01    | 0x24  | 0x01 | 0x0c     |
-//
-// See also:
-//
-// * MessagePack extensions https://www.tarantool.io/en/doc/latest/dev_guide/internals/msgpack_extensions/
-//
-// * An implementation in C language https://github.com/tarantool/decNumber/blob/master/decPacked.c
 package decimal
 
 import (

decimal/decimal.go

@@ -1,5 +1,42 @@
 // Package decimal with support of Tarantool's decimal data type.
 //
+// The package implements methods to encode and decode BCD.
+//
+// BCD (Binary-Coded Decimal) is a sequence of bytes representing decimal
+// digits of the encoded number (each byte has two decimal digits each encoded
+// using 4-bit nibbles), so byte >> 4 is the first digit and byte & 0x0f is the
+// second digit. The leftmost digit in the array is the most significant. The
+// rightmost digit in the array is the least significant.
+//
+// The first byte of the BCD array contains the first digit of the number,
+// represented as follows:
+//
+//     |  4 bits           |  4 bits           |
+//        = 0x                = the 1st digit
+//
+// (The first nibble contains 0 if the decimal number has an even number of
+// digits). The last byte of the BCD array contains the last digit of the
+// number and the final nibble, represented as follows:
+//
+//     |  4 bits           |  4 bits           |
+//        = the last digit    = nibble
+//
+// The final nibble represents the number's sign: 0x0a, 0x0c, 0x0e, 0x0f stand
+// for plus, 0x0b and 0x0d stand for minus.
+//
+// Examples:
+//
+// The decimal -12.34 will be encoded as 0xd6, 0x01, 0x02, 0x01, 0x23, 0x4d:
+//
+//     | MP_EXT (fixext 4) | MP_DECIMAL | scale |  1   |  2,3 |  4 (minus) |
+//     |        0xd6       |    0x01    | 0x02  | 0x01 | 0x23 | 0x4d       |
+//
+// The decimal 0.000000000000000000000000000000000010 will be encoded as
+// 0xc7, 0x03, 0x01, 0x24, 0x01, 0x0c:
+//
+//     | MP_EXT (ext 8) | length | MP_DECIMAL | scale |  1   | 0 (plus) |
+//     |      0xc7      |  0x03  |    0x01    | 0x24  | 0x01 | 0x0c     |
+//
 // Decimal data type supported in Tarantool since 2.2.
 //
 // Since: 1.7.0
@@ -13,6 +50,8 @@
 // * Tarantool issue for support decimal type https://github.com/tarantool/tarantool/issues/692
 //
 // * Tarantool module decimal https://www.tarantool.io/en/doc/latest/reference/reference_lua/decimal/
+//
+// * An implementation in C language https://github.com/tarantool/decNumber/blob/master/decPacked.c
 package decimal
 
 import (
@@ -83,9 +122,9 @@ func (decNum *Decimal) MarshalMsgpack() ([]byte, error) {
 // buffer length is not fixed and encoded by a number in a separate
 // field:
 //
-// +--------+-------------------+------------+===============+
-// | MP_EXT | length (optional) | MP_DECIMAL | PackedDecimal |
-// +--------+-------------------+------------+===============+
+//     +--------+-------------------+------------+===============+
+//     | MP_EXT | length (optional) | MP_DECIMAL | PackedDecimal |
+//     +--------+-------------------+------------+===============+
 func (decNum *Decimal) UnmarshalMsgpack(b []byte) error {
 	digits, err := decodeStringFromBCD(b)
 	if err != nil {