Expand <cfile>

This doesn't play well with :Git as it can result in a fugitive:// URL,
but it does make :Gedit <cfile> and :GBrowse <cfile> do what I mean.

autoload/fugitive.vim

@@ -1159,7 +1159,7 @@ function! fugitive#Object(...) abort
   endif
 endfunction
 
-let s:var = '\%(%\|#<\=\d\+\|##\=\)'
+let s:var = '\%(%\|#<\=\d\+\|##\=\|<cfile>\)'
 let s:flag = '\%(:[p8~.htre]\|:g\=s\(.\).\{-\}\1.\{-\}\1\)'
 let s:expand = '\%(\(' . s:var . '\)\(' . s:flag . '*\)\(:S\)\=\)'
 
@@ -1194,6 +1194,15 @@ function! s:ExpandVar(other, var, flags, esc, ...) abort
     let buffer = s:BufName(len(a:other) > 1 ? '#'. a:other[1:-1] : '%')
     let owner = s:Owner(buffer)
     return len(owner) ? owner : '@'
+  elseif a:var ==# '<cfile>'
+    let cfile = expand('<cfile>')
+    if v:version >= 704 && get(maparg('<Plug><cfile>', 'c', 0, 1), 'expr')
+      try
+        let cfile = eval(maparg('<Plug><cfile>', 'c'))
+      catch
+      endtry
+    endif
+    return cfile
   endif
   let flags = a:flags
   let file = s:DotRelative(fugitive#Real(s:BufName(a:var)), cwd)