Build potentially creates mixed newlines

[hynek]

As part of working on #419 I've noticed that the old change log is read using universal new lines, the fragments don't touch them, and finally the new file is written without touching.

This means that if a fragment has windows new lines, only the said fragment is rendered with them and the rest is not.

We should load the fragments with universal new lines too to be consistent.

That means that the change log has different new lines depending on the OS, but that might be a feature?

Another option is to make it an Option.

[adiroiban]

Thanks for the followup.

I think we should try to keep the configuration option to a minimum, as a general goal.
Add option only if really needed.

I guess that towncrier can look at the newlines from current file.

if it finds any \r\n pairs, it will enter Windows mode -
Any content is kept as it is, and new content is generated with \r\n

If it can't find \r\n it can assume Unix mode, and existing content is kept as it is, and new content generated with just \n.