cabal-gild version range pragma and minimum version flag

[BebeSparkelSparkel]

Just as with cabal-version it would be useful to have a cabal-gild-version [<version bounds>] pragma.

If the version bounds is not given, the bounds are filled in according to the cabal-gild pragmas and pragma arguments given in the cabal file.

If the version of the current cabal-gild is outside of the version bounds, cabal-gild should exit with a non-zero code. This feature should be added to the previous cabal-gild major versions.

[tfausak]

To be clear, you're suggesting a pragma like this?

-- cabal-gild: version ^>= 1.5.0

And then if you tried to use Gild 1.4 or 1.6 against that file, it would fail.

[BebeSparkelSparkel]

version has a name clash with my pr #101 so perhaps in the pr it should be changed to generated-with-version.

It seems that the bounds should match the cabal version bounds detailed in Version Constraints

Distribution.Types.VersionRange could be used to to easily parse this and withinRange to check the if the version is within the bounds.