doc: update the guidelines to reflect the current formatting rules

Signed-off-by: Jean-Noël Avila <[email protected]>

Documentation/CodingGuidelines

@@ -760,56 +760,60 @@ Markup:
 
 Synopsis Syntax
 
- Syntax grammar is formatted neither as literal nor as placeholder.
+ The synopsis (a paragraph with [synopsis] attribute) is automatically
+ formatted by the toolchain and does not need typesetting.
 
  A few commented examples follow to provide reference when writing or
  modifying command usage strings and synopsis sections in the manual
  pages:
 
  Possibility of multiple occurrences is indicated by three dots:
-   _<file>_...
+   <file>...
    (One or more of <file>.)
 
  Optional parts are enclosed in square brackets:
-   [_<file>_...]
+   [<file>...]
    (Zero or more of <file>.)
 
-   ++--exec-path++[++=++__<path>__]
+ An optional parameter needs to be typeset with unconstrained pairs
+   [<repository>]
+
+   --exec-path[=<path>]
    (Option with an optional argument.  Note that the "=" is inside the
    brackets.)
 
-   [_<patch>_...]
+   [<patch>...]
    (Zero or more of <patch>.  Note that the dots are inside, not
    outside the brackets.)
 
  Multiple alternatives are indicated with vertical bars:
-   [`-q` | `--quiet`]
-   [`--utf8` | `--no-utf8`]
+   [-q | --quiet]
+   [--utf8 | --no-utf8]
 
  Use spacing around "|" token(s), but not immediately after opening or
  before closing a [] or () pair:
-   Do: [`-q` | `--quiet`]
-   Don't: [`-q`|`--quiet`]
+   Do: [-q | --quiet]
+   Don't: [-q|--quiet]
 
  Don't use spacing around "|" tokens when they're used to separate the
  alternate arguments of an option:
-    Do: ++--track++[++=++(`direct`|`inherit`)]`
-    Don't: ++--track++[++=++(`direct` | `inherit`)]
+    Do: --track[=(direct|inherit)]
+    Don't: --track[=(direct | inherit)]
 
  Parentheses are used for grouping:
-   [(_<rev>_ | _<range>_)...]
+   [(<rev>|<range>)...]
    (Any number of either <rev> or <range>.  Parens are needed to make
    it clear that "..." pertains to both <rev> and <range>.)
 
-   [(`-p` _<parent>_)...]
+   [(-p <parent>)...]
    (Any number of option -p, each with one <parent> argument.)
 
-   `git remote set-head` _<name>_ (`-a` | `-d` | _<branch>_)
+   git remote set-head <name> (-a|-d|<branch>)
    (One and only one of "-a", "-d" or "<branch>" _must_ (no square
    brackets) be provided.)
 
  And a somewhat more contrived example:
-   `--diff-filter=[(A|C|D|M|R|T|U|X|B)...[*]]`
+   --diff-filter=[(A|C|D|M|R|T|U|X|B)...[*]]
    Here "=" is outside the brackets, because "--diff-filter=" is a
    valid usage.  "*" has its own pair of brackets, because it can
    (optionally) be specified only when one or more of the letters is