Use %i not %o for singular

References tpope#85.

Author: tpope

autoload/rails.vim

@@ -4423,6 +4423,7 @@ function! s:readable_projected(key, ...) dict abort
             \ 'h': toupper(root[0]) . tr(rails#underscore(root), '_', ' ')[1:-1],
             \ 'p': rails#pluralize(root),
             \ 'o': rails#singularize(root),
+            \ 'i': rails#singularize(root),
             \ '%': '%'}, a:0 ? a:1 : {})
       if suffix =~# '\.js\>'
         let ph.S = s:gsub(ph.S, '::', '.')

doc/rails.txt

@@ -782,7 +782,7 @@ variant of the variable portion:
 
 %s: original
 %p: pluralized
-%o: singularized ("one")
+%i: singularized
 %S: camelized
 %h: humanized