hledger-flow

I made some changes that will result in some formatting changes in some of the generated files:

• Removed the obsolete exclamation mark from the include directive

• Switched from hledger print to hledger import during statement import.

  hledger import uses your preferred commodity styles from your
  directives.journal to generate journals.

Other changes:

• Switched to GHC 9.0.1

Ensure that generated include files only contain files ending with .journal

Fixes #92

Add an optional --start-year command-line option for imports:

Import only from the specified year and onwards, ignoring previous years.
Valid values include a 4-digit year or 'current' for the current year.

• Make --enable-future-rundir the default, and deprecate the command-line option. To be removed in a future release.
• Ensure that the deepest rundir is the account directory, because the program doesn't generate include files correctly in directories below the account level.

• Add a new performance-related command-line option to import: --new-files-only. PR #89

  Don't regenerate transaction files if they are
  already present. This applies to hledger journal
  files as well as files produced by the preprocess and
  construct scripts.

• Generate monthly versions of the income statement in reports. A contribution by Max Linke

• Switch some usages of system-filepath over to path

  hledger-flow started as a collection of bash scripts that I translated into Haskell with the help of Turtle.

  Turtle uses the now deprecated system-filepath to represent all paths.

  I've had many filepath-related issues in hledger-flow.
  They were related to issues such as that 2 instances of the same directory would not be treated as equal, because one could have a trailing slash and the other not.
  Another issue that popped up was knowing wether a path is a file or a directory, and if it is absolute or relative.

  All of these issues are articulated in the path library:
  https://github.com/commercialhaskell/path

Imports

Improve support for importing a subset of journals: start importing only from the directory given as argument,
or the current directory, and generate only the relevant include files.

This is a behavioural change and (for now) it needs to be enabled with the --enable-future-rundir switch.
This will become the default behaviour in 0.14.x, at which time the switch will be removed.

Reports

Use the LEDGER_FILE env var (if set) when generating reports.
Default to the top-level all-years.journal if not set.

Other

Build with Stackage Nightly 2020-03-10 (ghc-8.8.3)

• Exit with an error code when any external script fails - https://github.com/apauley/hledger-flow/issues/28
• Capture external process output when doing parallel processing, in order to better prevent mangled concurrent output.
• Allow users to specify a path to an hledger executable.
• Display a user-friendly error message if hledger cannot be found - https://github.com/apauley/hledger-flow/issues/22