doc: document all file type

This adds it to the guide and the docs for the --type flag.

Fixes #1344, Closes #1472

CHANGELOG.md

@@ -20,6 +20,8 @@ Bug fixes:
 
 * [BUG #1335](https://github.com/BurntSushi/ripgrep/issues/1335):
   Fixes a performance bug when searching plain text files with very long lines.
+* [BUG #1344](https://github.com/BurntSushi/ripgrep/issues/1344):
+  Document usage of `--type all`.
 
 
 11.0.2 (2019-08-01)

GUIDE.md

@@ -411,6 +411,21 @@ alias rg="rg --type-add 'web:*.{html,css,js}'"
 or add `--type-add=web:*.{html,css,js}` to your ripgrep configuration file.
 ([Configuration files](#configuration-file) are covered in more detail later.)
 
+#### The special `all` file type
+
+A special option supported by the `--type` flag is `all`. `--type all` looks
+for a match in any of the supported file types listed by `--type-list`,
+including those added on the command line using `--type-add`. It's equivalent
+to the command `rg --type agda --type asciidoc --type asm ...`, where `...`
+stands for a list of `--type` flags for the rest of the types in `--type-list`.
+
+As an example, let's suppose you have a shell script in your current directory,
+`my-shell-script`, which includes a shell library, `my-shell-library.bash`.
+Both `rg --type sh` and `rg --type all` would only search for matches in
+`my-shell-library.bash`, not `my-shell-script`, because the globs matched
+by the `sh` file type don't include files without an extension. On the
+other hand, `rg --type-not all` would search `my-shell-script` but not
+`my-shell-library.bash`.
 
 ### Replacements
 

src/app.rs

@@ -2457,6 +2457,12 @@ fn flag_type(args: &mut Vec<RGArg>) {
     const LONG: &str = long!("\
 Only search files matching TYPE. Multiple type flags may be provided. Use the
 --type-list flag to list all available types.
+
+This flag supports the special value 'all', which will behave as if --type
+was provided for every file type supported by ripgrep (including any custom
+file types). The end result is that '--type all' causes ripgrep to search in
+\"whitelist\" mode, where it will only search files it recognizes via its type
+definitions.
 ");
     let arg = RGArg::flag("type", "TYPE").short("t")
         .help(SHORT).long_help(LONG)