Add --file flag

[Gabriella439]

This allows users to supply the Dhall expression by path instead of via
standard input. This also ensures that transitive imports are resolved
appropriately relative to the file's path.

In other words, instead of this:

$ dhall <<< './foo/bar.dhall'

Users can now do:

$ dhall --file foo/bar.dhall

[ocharles]

Have we thought about just using a positional argument for the file, and interpreting - as 'read from STDIN'? This is quite a common Unix idiom

…

On Mon, 13 May 2019, 11:11 am Gabriel Gonzalez, ***@***.***> wrote: This allows users to supply the Dhall expression by path instead of via standard input. This also ensures that transitive imports are resolved appropriately relative to the file's path. In other words, instead of this: $ dhall <<< './foo/bar.dhall' Users can now do: $ dhall --file foo/bar.dhall ------------------------------ You can view, comment on, or merge this pull request online at: #949 Commit Summary - Add `--file` flag File Changes - *M* dhall/src/Dhall/Main.hs <https://github.com/dhall-lang/dhall-haskell/pull/949/files#diff-0> (89) Patch Links: - https://github.com/dhall-lang/dhall-haskell/pull/949.patch - https://github.com/dhall-lang/dhall-haskell/pull/949.diff — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#949>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAFDDRGXDHMIWELMUXVQ4DPVDE4FANCNFSM4HML2KXQ> .

[Gabriella439]

@ocharles: The main reason I wasn't sure about using a positional argument is because I thought we might want to leave the door open for a parallel --expression flag for supplying the expression via the command line instead of standard input.

However, I can definitely add support for the idiom of - meaning STDIN