feature: Vim help-tags picker (#117)

* feature: Vim help-tags picker

* fix: filtered results were wrong because of missing `entry.value`

* fix: filtered (Vim only help) items are listed in results as empty
entries.

* fix: avoid search history pollution by replacing / in cmd returned by taglist() with search()

* fix: improve search() formatting

* fix: escape tilde in search() command

* fix: improve help-preview

* fix: improve search()

* fix: search() string fixes.

* fix: use no magic to do magic

Co-authored-by: TJ DeVries <devries.timothyj@gmail.com>

lua/telescope/make_entry.lua

@@ -284,4 +284,53 @@ function make_entry.gen_from_treesitter(opts)
   end
 end
 
+function make_entry.gen_from_tagfile(opts)
+  local help_entry, version
+  local delim = string.char(7)
+
+  local make_display = function(line)
+    help_entry = ""
+    display    = ""
+    version    = ""
+
+    line = line .. delim
+    for section in line:gmatch("(.-)" .. delim) do
+      if section:find("^vim:") == nil then
+        local ver = section:match("^neovim:(.*)")
+        if ver == nil then
+          help_entry = section
+        else
+          version = ver:sub(1, -2)
+        end
+      end
+    end
+
+    result = {}
+    if version ~= "" then -- some Vim only entries are unversioned
+      if opts.show_version then
+        result.display = string.format("%s [%s]", help_entry, version)
+      else
+        result.display = help_entry
+      end
+      result.value = help_entry
+    end
+
+    return result
+  end
+
+  return function(line)
+    local entry = {
+      entry_type = make_entry.types.GENERIC,
+
+    }
+    local d = make_display(line)
+    entry.valid   = next(d) ~= nil
+    entry.display = d.display
+    entry.value   = d.value
+    entry.ordinal = d.value
+
+    return entry
+  end
+end
+
 return make_entry