Created attachment 663275 [details]
en-US Revision History with a mix of different revnumber formats

Description of problem:
Publican 3 relies on a high level of consistency in the <revnumbers> of book Revision Histories to ensure that the Revision Histories of translations are sorted correctly when merged in.

When packaging the book in its original language, Publican does not have to sort the entries, so a much lower degree of consistency is permitted.

Authors therefore create revision histories that work fine for themselves, but which cause problems when translators try to package their work. (see attached example -- note the mix of x.y-z, x-z, x.y.z-r)

Version-Release number of selected component (if applicable):
3.0

How reproducible:
100%

Steps to Reproduce:
1. insert the attached Revision History into a book
2. run "publican package --lang en-US"
3. note that packaging works and Publican produces a valid SRPM
4. run "publican update_pot" and "publican update_po" for a language other than en-US
5. run "publican package" for that language
  
Actual results:
Publican cannot sort the entries from the translated language's Revision_History.xml file and packaging fails because the changelog is not in descending chronological order

Expected results:
And revision history that packages correctly in the original language should package correctly in translation (and any that would fail in translation should fail in the original language too).