Non-standard bibtex field 'issue' used by bibutils

[jayvdb]

The correct BibTeX field for journal issue is confusingly called number, and number is used for other output types - e.g. series number for books, etc..

Before 025424757030062e7abda68a4566ce728aa1622e , BibTeX number was mapped to CSL number, but that was corrected to map to 'issue'.

When a record contains both an issue and a number, bibutils emits both. If a record contains either an issue or a number, bibutils emits a number.

There is a comment explaining why in the bibutils source. https://github.com/jayvdb/bibutils-archive/blame/master/lib/bibtexout.c#L508

/*
 * from Tim Hicks:
 * I'm no expert on bibtex, but those who know more than I on our mailing 
 * list suggest that 'issue' isn't a recognised key for bibtex and 
 * therefore that bibutils should be aliasing IS to number at some point in 
 * the conversion.
 *
 * Therefore prefer outputting issue/number as number and only keep
 * a distinction if both issue and number are present for a particular
 * reference.
 */

static void output_issue_number( FILE *fp, fields *info, int format_opts ) ...

I suggest that citeproc-py follows suit.

[jayvdb]

No particular rush for me on this one, as I have a workaround (https://github.com/jayvdb/pubpdf/commit/6e0d9e5131d5b449f98928245ef3f1a332313040), but other uses might be surprised by the wrong number appearing for the issue.