Changes to Distribution.ParseUtils.ppField generate invalid .conf file

[ddssff]

The new ppField function in version 1.20, when passed a description with a leading newline, now generates a field with a leading blank line and no ".":

ppField "description" (text "\n        this is a description\n        second line")
Loading package pretty-1.1.1.1 ... linking ... done.
description:

        this is a description
        second line

When written to the package.conf file this is an illegal format. Previously the output was

> ppField "description" (text "\n        this is a description\n        second line")
description: 
        this is a description
        second line

An example of a .cabal file for which this causes problems is in the vector package.

[23Skidoo]

See @dan-t's comment here. What kinds of failures does this cause?

[dan-t]

The prefix newline is interpreted as an empty line in the description.

[23Skidoo]

Fixed by #1998.