feat: add shorten_len option for path shortening

- adds option to configure the length of shortened parts of filenames
- only affects paths when "shorten" is in `path_display`
- reimplemented based on changes in nvim-telescope#473 and nvim-telescope#839

lua/telescope/config.lua

@@ -202,6 +202,21 @@ local telescope_defaults = {
     Default: {}]]
   },
 
+  shorten_len = { 1, [[
+    Determines the length of the shortened portions of a filepath.
+
+    e.g. for a path like
+      `alpha/beta/gamma/delta.txt`
+    setting `shorten_len = 1` will give a path like:
+      `a/b/g/delta.txt`
+    when "shorten" is present in `path_display`.
+    Similarly, `shorten_len = 2` will give a path like:
+      `al/be/ga/delta.txt`
+    when "shorten" is present in `path_display`.
+
+    Default: 1]]
+  },
+
   borderchars = { { "─", "│", "─", "│", "╭", "╮", "╯", "╰" } },
 
   get_status_text = {

lua/telescope/path.lua

@@ -21,29 +21,12 @@ path.make_relative = function(filepath, cwd)
   return filepath
 end
 
-path.shorten = (function()
-  if jit then
-    local ffi = require('ffi')
-    ffi.cdef [[
-    typedef unsigned char char_u;
-    char_u *shorten_dir(char_u *str);
-    ]]
-
-    return function(filepath)
-      if not filepath then
-        return filepath
-      end
-
-      local c_str = ffi.new("char[?]", #filepath + 1)
-      ffi.copy(c_str, filepath)
-      return ffi.string(ffi.C.shorten_dir(c_str))
-    end
-  else
-    return function(filepath)
-      return filepath
-    end
-  end
-end)()
+-- In most cases it is better to use `utils.path_shorten`
+-- as it handles cases for `len` being things other than
+-- a positive integer.
+path.shorten = function(filepath,len)
+  return require'plenary.path'.new(filepath):shorten(len)
+end
 
 path.normalize = function(filepath, cwd)
   filepath = path.make_relative(filepath, cwd)

lua/telescope/utils.lua

@@ -251,8 +251,14 @@ utils.diagnostics_to_tbl = function(opts)
   return items
 end
 
-utils.path_shorten = function(file)
-  return Path:new(file):shorten()
+utils.path_shorten = function(filename,len)
+  if len == nil or len == true then
+    return Path:new(filename):shorten(1)
+  elseif tonumber(len) > 0 then
+    return Path:new(filename):shorten(tonumber(len))
+  else
+    error('Invalid value for `len`. Acceptable values are `nil`, `true` and positive integers.')
+  end
 end
 
 utils.path_tail = (function()
@@ -273,6 +279,7 @@ end
 
 utils.transform_path = function(opts, path)
   local path_display = utils.get_default(opts.path_display, require('telescope.config').values.path_display)
+  local shorten_len = utils.get_default(opts.shorten_len, require('telescope.config').values.shorten_len)
 
   local transformed_path = path
 
@@ -301,7 +308,7 @@ utils.transform_path = function(opts, path)
     end
 
     if vim.tbl_contains(path_display, "shorten") then
-      transformed_path = Path:new(transformed_path):shorten()
+      transformed_path = utils.path_shorten(transformed_path, shorten_len)
     end
   end
 
@@ -439,7 +446,7 @@ utils.transform_devicons = (function()
       end
 
       local icon, icon_highlight = devicons.get_icon(filename, string.match(filename, '%a+$'), { default = true })
-      local icon_display = (icon or ' ') .. ' ' .. display
+      local icon_display = (icon or ' ') .. ' ' .. (display or '')
 
       if conf.color_devicons then
         return icon_display, icon_highlight