Keep a newline in an entry from splitting the fifo payload

The fifo is read a line at a time, but ':GFiles' reads NUL separated names
from 'git ls-files -z', so an entry can hold a newline. It arrived as two
callbacks, and a fragment that named another tracked file opened that one
instead.

The binding swaps the newline for \1 and s:show_entry puts it back, so a
multi-line entry stays one payload.

autoload/fzf/vim.vim

@@ -655,7 +655,9 @@ endfunction
 " Scopes the options s:goto_entry needs, which every early return has to
 " restore, hence the split.
 function! s:show_entry(winid, bufnr, dir, kind, entry) abort
-  if empty(a:entry)
+  " Undo the newline escaping the binding applies
+  let entry = substitute(a:entry, nr2char(1), "\n", 'g')
+  if empty(entry)
     return
   endif
   " 'acd' would move the cwd on the first open, and s:ag_to_qf resolves a
@@ -667,7 +669,7 @@ function! s:show_entry(winid, bufnr, dir, kind, entry) abort
     let [&magic, &wrapscan] = [0, 1]
   endif
   try
-    call s:goto_entry(a:winid, a:bufnr, a:dir, a:kind, a:entry)
+    call s:goto_entry(a:winid, a:bufnr, a:dir, a:kind, entry)
   finally
     let [&magic, &wrapscan, &acd] = [magic, wrapscan, acd]
   endtry
@@ -746,7 +748,7 @@ function! s:goto_entry(winid, bufnr, dir, kind, entry) abort
           \ printf('keepjumps call cursor(%d, %d)', str2nr(parts[2]), str2nr(parts[3])),
           \ 'normal! zvzz']
   elseif a:kind ==# 'grep'
-    " Vim sends one line per callback, so multi-line entries arrive in pieces
+    " A multi-line match arrives whole, and s:ag_to_qf reads the first line
     try
       let entry = s:ag_to_qf(entry)
     catch
@@ -885,7 +887,10 @@ function! s:add_hints(spec, bang) abort
       let Exit = get(a:spec, 'exit', 0)
       let a:spec.exit = { code -> [fzf#vim#ipc#stop(fifo),
             \ type(Exit) == s:TYPE.funcref ? call(Exit, [code]) : 0] }
-      call s:prepend_opts(a:spec, ['--bind', key.':execute-silent:printf ''%s\n'' {} > '.fzf#shellescape(fifo)])
+      " The fifo is read a line at a time, but an entry can contain a newline
+      " where the source is NUL separated, as ':GFiles' is. Swap it for a
+      " byte no path is going to hold and put it back in s:show_entry
+      call s:prepend_opts(a:spec, ['--bind', key.':execute-silent:{ printf ''%s'' {} | tr ''\n'' ''\1''; echo; } > '.fzf#shellescape(fifo)])
       let entries = [[s:key_label(key), 'Show']] + (type(entries) == s:TYPE.list ? entries : [])
       let started = fifo
       let taken = s:split_keys(key)