Add Grepping Through The Vim Help Files as a vim til.

README.md

@@ -294,6 +294,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 - [Filter Lines Through An External Program](vim/filter-lines-through-an-external-program.md)
 - [Format Long Lines To Text Width](vim/format-long-lines-to-text-width.md)
 - [Generate and Edit Rails Migration](vim/generate-and-edit-rails-migration.md)
+- [Grepping Through The Vim Help Files](vim/grepping-through-the-vim-help-files.md)
 - [Head of File Name](vim/head-of-file-name.md)
 - [Help For Non-Normal Mode Features](vim/help-for-non-normal-mode-features.md)
 - [Horizontal to Vertical and Back Again](vim/horizontal-to-vertical-and-back-again.md)

vim/grepping-through-the-vim-help-files.md

@@ -0,0 +1,17 @@
+# Grepping Through The Vim Help Files
+
+Trying to look up the help file for a Vim feature, but you cannot quite
+remember the right keyword? Use `:helpgrep`. With `:helpgrep`, you can
+search across all of the Vim help files for not just the specific keywords,
+but any pattern of text. For instance, if you want to find where
+`substitution` is mentioned in the help files, try:
+
+```
+:helpgrep substitution
+```
+
+It makes a list of all occurrences in the quick fix window and then opens up
+a split with the cursor on the line of the first occurrence. You can then
+hit `:copen` to see the rest of the entries.
+
+See `:h helpgrep` for more details.