feat: implement -R and -f flags for regional settings and codepage

[dlevy-msft-sql]

Summary

Implements the -R flag for locale-aware formatting and -f flag for codepage/encoding control, matching ODBC sqlcmd behavior.

Changes

-R (Regional Settings)

• Detect user locale from Windows LCID or Unix environment variables
• Apply regional formatting to:
  • DECIMAL/NUMERIC/MONEY: Locale-specific thousand separators
  • DATE/TIME/DATETIME: Locale-specific date and time formats

-f (Code Page)

• Specifies input/output encoding
• Format: codepage | i:codepage[,o:codepage] | o:codepage[,i:codepage]
• Use 65001 for UTF-8
• --list-codepages shows all supported encodings

Usage

# Regional formatting
sqlcmd -S server -R -Q "SELECT GETDATE(), 1234.56"

# UTF-8 output
sqlcmd -S server -f 65001 -Q "SELECT name FROM sys.databases"

[Copilot]

Pull request overview

This PR implements locale-aware formatting for query results when -R is specified and introduces configurable code page handling for input/output, plus associated CLI flags and documentation updates.

Changes:

• Add RegionalSettings with platform-specific locale detection (detectUserLocale) and integrate it into the default formatter so that -R controls locale-aware numeric and date/time formatting.
• Introduce code page parsing and encoding support (ParseCodePage, GetEncoding, SupportedCodePages) and wire it into file input (:R), output (:OUT, :ERROR), and new CLI flags -f/--code-page and --list-codepages.
• Extend tests to cover regional formatting helpers, formatter construction, code page parsing/encoding, CLI argument parsing/validation, and document new -R and -f behaviors in README.md.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
pkg/sqlcmd/sqlcmd.go	Adds CodePage *CodePageSettings to Sqlcmd and updates IncludeFile to honor configured input code pages or BOM-based UTF-16 auto-detection when reading :R files.
pkg/sqlcmd/regional.go	Implements RegionalSettings (locale detection via detectUserLocale), number/money/date/time formatting, and locale-specific separators and date/time layouts.
pkg/sqlcmd/regional_windows.go	Windows-only locale detection using GetUserDefaultLCID and a mapping from LCID values to BCP 47 language tags.
pkg/sqlcmd/regional_linux.go	Linux-only locale detection from LC_ALL, LC_MESSAGES, and LANG, plus Unix locale string parsing to BCP 47 tags.
pkg/sqlcmd/regional_darwin.go	macOS-only locale detection using environment variables or defaults read -g AppleLocale, with Unix locale parsing similar to Linux.
pkg/sqlcmd/regional_test.go	Unit tests for RegionalSettings enable/disable behavior, NULL/empty handling, separators, date/time format selection, helper functions, and basic formatter construction with/without regional settings.
pkg/sqlcmd/format.go	Extends sqlCmdFormatterType with a regional *RegionalSettings field, adds NewSQLCmdDefaultFormatterWithRegional, and applies regional formatting to numeric and date/time columns in scanRow when -R is enabled.
pkg/sqlcmd/commands.go	Updates :OUT and :ERROR commands to write using either UTF-16 (for -u) or a configured output code page via GetEncoding, falling back to raw UTF-8 when appropriate.
pkg/sqlcmd/codepage.go	Adds CodePageSettings, ParseCodePage for -f syntax, GetEncoding for many Windows and related code pages, and SupportedCodePages metadata for listing.
pkg/sqlcmd/codepage_test.go	Tests ParseCodePage (including error cases and specific code pages) and GetEncoding for successful encodings and error handling for unsupported code pages.
cmd/sqlcmd/sqlcmd.go	Extends SQLCmdArguments with CodePage, ListCodePages, and UseRegionalSettings, validates -f, adds --code-page, --list-codepages, and -R flag wiring, lists supported code pages when requested, parses code page settings before running, and uses NewSQLCmdDefaultFormatterWithRegional to honor -R.
cmd/sqlcmd/sqlcmd_test.go	Adds CLI argument parsing tests for -f variations and --list-codepages, plus invalid -f cases that exercise Validate; reuses existing test harness for command-line normalization and error formatting.
README.md	Updates the description of -R to reflect new locale-aware formatting behavior and documents the new -f code page option and --list-codepages helper, including examples of supported code pages.

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[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

[Copilot]

NewRegionalSettings calls detectUserLocale, but this function is only implemented in regional_windows.go, regional_linux.go, and regional_darwin.go using GOOS-specific build tags. On other platforms (for example freebsd or openbsd), this package will fail to compile because detectUserLocale has no definition. Consider adding a fallback implementation in a regional_other.go file with a complementary build tag (e.g. //go:build !windows && !linux && !darwin) that returns a sensible default like language.English so cross-compilation and tests on non-main platforms continue to work.

[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated no new comments.