implement new unique_tail formatter. resolves #230.

autoload/airline/extensions/tabline/formatters.vim

@@ -10,10 +10,6 @@ let s:buf_modified_symbol = g:airline_symbols.modified
 function! airline#extensions#tabline#formatters#default(bufnr, buffers)
   let _ = ''
 
-  if s:buf_nr_show
-    let _ .= printf(s:buf_nr_format, a:bufnr)
-  endif
-
   let name = bufname(a:bufnr)
   if empty(name)
     let _ .= '[No Name]'
@@ -25,10 +21,40 @@ function! airline#extensions#tabline#formatters#default(bufnr, buffers)
     endif
   endif
 
+  return s:wrap_name(a:bufnr, _)
+endfunction
+
+function! airline#extensions#tabline#formatters#unique_tail(bufnr, buffers)
+  let duplicates = {}
+  let tails = {}
+  let map = {}
+  for nr in a:buffers
+    let name = bufname(nr)
+    if empty(name)
+      let map[nr] = '[No Name]'
+    else
+      let tail = fnamemodify(name, ':t')
+      if has_key(tails, tail)
+        let duplicates[nr] = nr
+      endif
+      let tails[tail] = 1
+      let map[nr] = s:wrap_name(nr, tail)
+    endif
+  endfor
+
+  for nr in values(duplicates)
+    let map[nr] = s:wrap_name(nr, fnamemodify(bufname(nr), ':p:.'))
+  endfor
+
+  return map[a:bufnr]
+endfunction
+
+function! s:wrap_name(bufnr, buffer_name)
+  let _ = s:buf_nr_show ? printf(s:buf_nr_format, a:bufnr) : ''
+  let _ .= a:buffer_name
   if getbufvar(a:bufnr, '&modified') == 1
     let _ .= s:buf_modified_symbol
   endif
-
   return _
 endfunction
 

doc/airline.txt

@@ -386,6 +386,11 @@ eclim <https://eclim.org>
 <
     * configure collapsing parent directories in buffer name. >
       let g:airline#extensions#tabline#fnamecollapse = 1
+
+  " The `unique_tail` algorithm will display the tail of the filename, unless
+  " there is another file of the same name, in which it will display it along
+  " with the containing parent directory.
+  let g:airline#extensions#tabline#formatter = 'unique_tail'
 <
 * configure the minimum number of buffers needed to show the tabline. >
   let g:airline#extensions#tabline#buffer_min_count = 0