Changelog of @hackage/optparse-applicative 0.9.0

Version 0.9.0 (23 May 2014)

Help page formatting. Added columns preference modifier, which can be used to specify the number of columns in the output terminal.
Deprecated arguments and arguments1 builders. Using many and some on a parser built using argument now returns a multiple argument parsers that behaves correctly with respect to --.
Fixed bugs
- #60 - runParser can't be called
- #64 - --help behaviour

Added builders for options that always fail. This makes it easier to create options that just print an error message or display some brief information and then exit (like --version).
Added execParserMaybe and customExecParserMaybe functions (pull request #49).
Fixed bugs
- #47 - Current master prints help text instead of error
- #48 - Can we have an eitherReader convenience function?
- #50 - In order parsing problems.
- #22 - Strict (no-intersperse) arguments

There is a new parser preference noBacktrack, that controls whether how a failure in a subparser is propagated. By default, an unknown option in a subparser causes the option to be looked up in parent parsers. When noBacktrack is used, this behavior is disabled. This is useful to implement subcommands that have no relations with their parent commands.
Fixed bugs
- #35 - Artifacts of "hidden"
- #31 - Backtracking on commands
- #25 - Allow for using Maybe in options types to specify optional arguments
- #34 - No simple/obvious way to add a --version switch
- #29 - Document Mod
- #26 - Improve docs for the Arrow interface

Fewer GHC extensions required.
Improved error handling: unrecognized options now result in an error message.
By default, the full help text is not displayed on parse errors anymore. This behavior can be controlled with the prefShowHelpOnError field of ParserPrefs.
The (&) operator is now deprecated. Modifiers can still be combined using (<>) or mappend.
Fixed bugs
- #37 - Use (<>) instead of (&) in documentation

Fixed bugs
- #27 - Please include the test source files in the cabal sdist tarball

Brief help text for nested commands now shows the full command line.
Fixed inefficiency in the arguments parsers for long argument lists.
Added automatic bash completion.
Added disambiguate modifier for prefs, which enabled automatic disambiguation of option abbreviations. With disambiguation on, a command line like:
```
  foo --out
```
will match an option called --output, as long as its the only one starting with the string out.
Added briefDesc modifier.
Fixed bugs
- #8 - Long options not disambiguated
- #10 - Shell completions
- #16 - Possible memory leak?

Added new showDefault and showDefaultWith modifiers, which will result in the default value (if present) to be displayed in the help text.
Fixed bugs
- #12 - Optionally display default values in help

Parser is now an instance of Alternative. This makes it possible to build certain complex parsers that were not definable before. See tests/Examples/Alternatives.hs for a simple example.
Removed multi modifier. You can now use the many or some methods from Alternative, instead, to create parsers for options that can appear more than once.
Added new flag' builder that returns a flag without a default value. Although flags without default values were not useful before, with the addition of Alternative combinators, they do have valid use cases.
Added new internal modifier for options. An internal option is completely invisible in the help text.
Added a new customExecParser function, which takes an additional ParserPrefs parameter. At the moment, ParserPrefs can only be used to control how many-valued option metavars are displayed in the help text. Setting its multiSuffix field to e.g. ... will result in an arguments parser description like [METAVAR]....
Fixed bugs
- #6 - "arguments" swallows options
- #5 - Help formatting for "arguments" misleading

Improved error reporting internals
Removed template-haskell dependency
Fixed bugs: * #3 - No help for subparsers * #4 - Extra empty lines around command list