bibtex-entry-update is an interactive compiled Lisp function in `bibtex.el'.

(bibtex-entry-update &optional ENTRY-TYPE)

Update an existing BibTeX entry.
In the BibTeX entry at point, make new fields for those items that may occur
according to `bibtex-field-list', but are not yet present.
Also, add field delimiters to numerical fields if they are not present.
If ENTRY-TYPE is non-nil, change first the entry type to ENTRY-TYPE.
When called interactively with a prefix arg, query for a value of ENTRY-TYPE.