Initial version of go-sqlcmd

[shueybubbles]

There's a LONG way to go but basic interactive mode with file output is ready for main!

What do we have in this version?

• Custom batch separator (-c)
• Windows and SQL auth support (-C, -d, -E, -P, -U)
• Using environment variables as default values for some command line arguments (eg SQLCMDSERVER, SQLCMDPASSWORD)
• Output to file (-O)
• Interactive console mode
• Multiline comments and quoted strings change the prompt to ~ like this:

1> select 'this is a multiline
2~ string
3~ see?'
4> /* this is a multiline
5~ comment */

• Screen width limiting when SQLCMDCOLWIDTH > 0
  eg with SQLCMDCOLWIDTH == 10 before running go-sqlcmd:

1> select 'this is a long name is it not' as name
2> go
name


----------
----------
---------
this is a
long name
is it not

• Go command, including repeat count
• Out, Error commands to redirect output
• Quit command

What's obviously missing or broken?

• Printing of messages. Needs driver support first per Get SQL Server Messages / PRINT command denisenkom/go-mssqldb#221
• anything related to using system- or user-default time formats. Golang seems to lack any way to query the system for the default format
• Most commands
• Variable evaluation
• Input from files
• Some SQL types don't render the same as native sqlcmd or even the same as ssms. Varbinary(max) acts differently in all 3.

select convert(varbinary(max), '123456') as mybinary

SSMS: 
mybinary
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
0x313233343536

(1 row affected)

SQLCMD seems to miscalculate column width for varbinary(max) and truncates it based on the column name length.

1> select convert(varbinary(max), '123456') as mybinary
2> go
mybinary
--------
0x313233

go-sqlcmd is not converting the data correctly. It'll need some debugging.

1>  select convert(varbinary(max), '123456') as mybinary
2> go
mybinary                                                                                                                                                                                                                                     
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
0x123456                  

[ascarter]

Lots of structural and style comments. My biggest suggestion is to alter the overall project layout and adapt it to support your future utilities you described.

[ascarter]

You can use:

 return fmt.Errorf("%s Error occurred while opening or operating on file %q (Reason: %v).", ErrorPrefix, path, err)

[ascarter]

Can use fmt.Errorf