doc: escape braces in AsciiDoc

This commit fixes a bug where AsciiDoc would drop any line containing a
'{foo}' because it interpreted it as an undefined attribute reference:

> Simple attribute references take the form {<name>}. If the attribute name
> is defined its text value is substituted otherwise the line containing the
> reference is dropped from the output.

See: https://www.methods.co.nz/asciidoc/chunked/ch30.html

We fix this by simply replacing all occurrences of '{' and '}' with
their escaped forms: '&#123;' and '&#125;'.

Fixes #1101

build.rs

@@ -168,7 +168,12 @@ fn formatted_arg(arg: &RGArg) -> io::Result<String> {
 }
 
 fn formatted_doc_txt(arg: &RGArg) -> io::Result<String> {
-    let paragraphs: Vec<&str> = arg.doc_long.split("\n\n").collect();
+    let paragraphs: Vec<String> = arg.doc_long
+        .replace("{", "&#123;")
+        .replace("}", r"&#125;")
+        .split("\n\n")
+        .map(|s| s.to_string())
+        .collect();
     if paragraphs.is_empty() {
         return Err(ioerr(format!("missing docs for --{}", arg.name)));
     }

src/app.rs

@@ -788,17 +788,17 @@ to one of eight choices: red, blue, green, cyan, magenta, yellow, white and
 black. Styles are limited to nobold, bold, nointense, intense, nounderline
 or underline.
 
-The format of the flag is `{type}:{attribute}:{value}`. `{type}` should be
-one of path, line, column or match. `{attribute}` can be fg, bg or style.
-`{value}` is either a color (for fg and bg) or a text style. A special format,
-`{type}:none`, will clear all color settings for `{type}`.
+The format of the flag is '{type}:{attribute}:{value}'. '{type}' should be
+one of path, line, column or match. '{attribute}' can be fg, bg or style.
+'{value}' is either a color (for fg and bg) or a text style. A special format,
+'{type}:none', will clear all color settings for '{type}'.
 
 For example, the following command will change the match color to magenta and
 the background color for line numbers to yellow:
 
     rg --colors 'match:fg:magenta' --colors 'line:bg:yellow' foo.
 
-Extended colors can be used for `{value}` when the terminal supports ANSI color
+Extended colors can be used for '{value}' when the terminal supports ANSI color
 sequences. These are specified as either 'x' (256-color) or 'x,x,x' (24-bit
 truecolor) where x is a number between 0 and 255 inclusive. x may be given as
 a normal decimal number or a hexadecimal number, which is prefixed by `0x`.