Vim Folding for RIS files

gistfile1.vim

" Some folding functions for using Vim with RIS files...

" Lines starting with 'TY  -' trigger folds

set foldexpr=RIS_Fold()
set foldmethod=expr
fun! RIS_Fold()
    let thisline = getline(v:lnum)
    if thisline =~ '^TY  -.*'
        return '>1'
    else
        return '='
    endif
endfun

" When entry is folded, display the ID, or, if no ID, author and title.

set foldtext=RIS_FoldText()
fun! RIS_FoldText()
    let linenum = v:foldstart + 1
    let result = ''
    while linenum < v:foldend
       if getline(linenum) =~ '^ID.*'
           return substitute(getline(linenum), '^ID  - ', '', '')
       elseif getline(linenum) =~ '^AU.*'
           let result = substitute(getline(linenum), '^AU  - ', '', '') . '. ' . result
       elseif getline(linenum) =~ '^TI.*'
           let result = result . substitute(getline(linenum), '^TI  - ', '', '')
       endif
       let linenum += 1
    endwhile
    return result
endfun

For plain-text management of bibliographic data, RIS is promising because it is so simple. There is a vim-ris plugin here. The syntax file works okay, though it could use some work. I haven't been able to get the rest of that plugin working.

Other functions that would be nice implement in a vim RIS plugin: sorting entries by field; autogenerating citekeys (IDs); opening links to URLs and local files; displaying skim comments... Importing and exporting to other formats could be handled by bibutils.