fix(pickers): improve CRLF line splitting support for windows (#3127)

* fix(help_tags): show help tags on windows (#3126)

On Windows, `builtin.help_tags` picker does not show any help tags.

To fix this, the following changes are needed:

1. `util.path_tail` checks unix separator `/` on Windows and leave the
original implementation intact on unix systems.

2. Line endings should be taken carefully on Windows. `vim.split` with
   only newline `\n` character as separator may result in unexpected
   crash when parsing large files. When splits on lines are needed, call
   it with `\r?\n`, or even set up a wrapper function in utils is more
   prefered.

Fixes #3126

* fix: handle cross platform line splits

lua/telescope/utils.lua

@@ -216,13 +216,25 @@ end)()
 utils.path_tail = (function()
   local os_sep = utils.get_separator()
 
-  return function(path)
-    for i = #path, 1, -1 do
-      if path:sub(i, i) == os_sep then
-        return path:sub(i + 1, -1)
+  if os_sep == "/" then
+    return function(path)
+      for i = #path, 1, -1 do
+        if path:sub(i, i) == os_sep then
+          return path:sub(i + 1, -1)
+        end
       end
+      return path
+    end
+  else
+    return function(path)
+      for i = #path, 1, -1 do
+        local c = path:sub(i, i)
+        if c == os_sep or c == "/" then
+          return path:sub(i + 1, -1)
+        end
+      end
+      return path
     end
-    return path
   end
 end)()
 
@@ -727,4 +739,16 @@ utils.reverse_table = function(input_table)
   return temp_table
 end
 
+utils.split_lines = (function()
+  if utils.iswin then
+    return function(s, opts)
+      return vim.split(s, "\r?\n", opts)
+    end
+  else
+    return function(s, opts)
+      return vim.split(s, "\n", opts)
+    end
+  end
+end)()
+
 return utils