new option: g:startify_custom_indices

People can now choose to create their own index mapping instead of
having the default behaviour of increasing numbers.

Closes #17.

doc/startify.txt

@@ -144,6 +144,34 @@ name contained in this list.
 Example: let g:startify_skiplist_server = [ 'GVIM' ]
 
 
+============-
+
+    let g:startify_custom_indices = []
+
+Use any list of strings as custom indices instead of increasing numbers. If
+there are more paths to fill in the startify buffer than actual items in the
+custom list, the rest will be filled up using the default numbering scheme
+starting from 0.
+
+NOTE: There is no sanitizing going on, so you should know what you do!
+
+E.g. you don't want to use duplicates. Same for 'e', 'i', 'q'. Actually you
+can use them, but they would be overwritten by mappings for creating the empty
+buffer and quitting. You may want to keep 'j' and 'k', too.
+
+Example: let g:startify_custom_indices = ['a','s','d','f']
+
+This would result in:
+
+    [a]  /last/recently/used/file1
+    [s]  /last/recently/used/file2
+    [d]  /last/recently/used/file3
+    [f]  /last/recently/used/file4
+    [0]  /last/recently/used/file5
+    [1]  /last/recently/used/file6
+    etc.
+
+
 ============-
 
     let g:startify_unlisted_buffer = 1

plugin/startify.vim

@@ -60,8 +60,9 @@ function! s:insane_in_the_membrane() abort
       if !filereadable(expfname) || (exists('g:startify_skiplist') && startify#is_in_skiplist(expfname))
         continue
       endif
-      call append('$', '   ['. cnt .']'. repeat(' ', 3 - strlen(string(cnt))) . fname)
-      execute 'nnoremap <buffer> '. cnt .' :edit '. startify#escape(fname) .' <bar> lcd %:h<cr>'
+      let index = s:get_index_as_string(cnt)
+      call append('$', '   ['. index .']'. repeat(' ', (3 - strlen(index))) . fname)
+      execute 'nnoremap <buffer> '. index .' :edit '. startify#escape(fname) .' <bar> lcd %:h<cr>'
       let cnt += 1
       if (cnt == numfiles)
         break
@@ -74,9 +75,10 @@ function! s:insane_in_the_membrane() abort
   if get(g:, 'startify_show_sessions', 1) && !empty(sfiles)
     call append('$', '')
     for i in range(len(sfiles))
-      let idx = i + cnt
-      call append('$', '   ['. idx .']'. repeat(' ', 3 - strlen(string(idx))) . fnamemodify(sfiles[i], ':t:r'))
-      execute 'nnoremap <buffer> '. idx .' :source '. startify#escape(sfiles[i]) .'<cr>'
+      let idx = (i + cnt)
+      let index = s:get_index_as_string(idx)
+      call append('$', '   ['. index .']'. repeat(' ', (3 - strlen(index))) . fnamemodify(sfiles[i], ':t:r'))
+      execute 'nnoremap <buffer> '. index .' :source '. startify#escape(sfiles[i]) .'<cr>'
     endfor
     let cnt = idx
   endif
@@ -85,8 +87,9 @@ function! s:insane_in_the_membrane() abort
     call append('$', '')
     for fname in g:startify_bookmarks
       let cnt += 1
-      call append('$', '   ['. cnt .']'. repeat(' ', 3 - strlen(string(cnt))) . fname)
-      execute 'nnoremap <buffer> '. cnt .' :edit '. startify#escape(fname) .' <bar> lcd %:h<cr>'
+      let index = s:get_index_as_string(cnt)
+      call append('$', '   ['. index .']'. repeat(' ', (3 - strlen(index))) . fname)
+      execute 'nnoremap <buffer> '. index .' :edit '. startify#escape(fname) .' <bar> lcd %:h<cr>'
     endfor
   endif
 
@@ -118,6 +121,16 @@ function! s:insane_in_the_membrane() abort
   call cursor(special ? 4 : 2, 5)
 endfunction
 
+" Function: s:get_index_as_string {{{1
+function! s:get_index_as_string(idx) abort
+  if exists('g:startify_custom_indices')
+    let listlen = len(g:startify_custom_indices)
+      return (a:idx < listlen) ? g:startify_custom_indices[a:idx] : string(a:idx - listlen)
+  else
+    return string(a:idx)
+  endif
+endfunction
+
 " Function: s:set_cursor {{{1
 function! s:set_cursor() abort
   let s:line_old = exists('s:line_new') ? s:line_new : 5

syntax/startify.vim

@@ -11,7 +11,7 @@ let s:sep = startify#get_sep()
 
 syntax  match  StartifySpecial  /\V<empty buffer>\|<quit>/
 syntax  match  StartifyBracket  /\[\|\]/
-syntax  match  StartifyNumber   /\v\[[eq[:digit:]]+\]/hs=s+1,he=e-1 contains=StartifyBracket
+syntax  match  StartifyNumber   /\v\[.+\]/hs=s+1,he=e-1 contains=StartifyBracket
 syntax  match  StartifyFile     /.*/ contains=StartifyBracket,StartifyNumber,StartifyPath,StartifySpecial
 
 execute 'syntax match StartifySlash /\'. s:sep .'/'