Use two options and less surprising behaviour. Notes:
* a recognised suffix on the output file name can set the format
* but --output-format always wins
* -o - means stdout
* currently these are command-specific options on balance, print, register
* later, --output-file should become a global option
* and --output-format should be available at least on all commands which
support multiple formats. Each command may support a different set of
output formats, which should be listed in its command line help.
Can be helpful when reading Ledger files, where assertions may have
different semantics; or for getting some answers from your journal
to help you fix your assertions.
Could be called --no-assertions, but this might create surprise when it
has an effect contrary to --no-new-accounts.
I had to add another flag throughout the parsers & journal read
functions, ok for now.
In general, when cabal CPP macros like min_PKG are used, they should
be made optional. If they are not present, assume a developer is
building and choose the latest libs.
Revisiting the "directory 1.2 can be installed with older GHC, so we'd better pin it in the cabal file" change.
Requiring directory 1.2 made hledger-web uninstallable with GHC < 7.6 because current yesod depends on ghc
which depends on a particular directory version and can't be upgraded. This is a smarter fix, which should let
all hledger packages build with whatever directory version is installed.
hledger now requires directory >= 1.2. This might make installation
more complex on old GHC versions; if it turns out to be needed,
perhaps it can be conditionalised again, more accurately, in the cabal file.
