doc: rework CodingGuidelines with new formatting rules

Literal and placeholder formatting is more heavily enforced, with some
asciidoc magic. Basically, the markup is preserved everywhere.

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

Documentation/CodingGuidelines

@@ -641,15 +641,15 @@ Writing Documentation:
   - Prefer succinctness and matter-of-factly describing functionality
     in the abstract.  E.g.
 
-     --short:: Emit output in the short-format.
+     `--short`:: Emit output in the short-format.
 
     and avoid something like these overly verbose alternatives:
 
-     --short:: Use this to emit output in the short-format.
-     --short:: You can use this to get output in the short-format.
-     --short:: A user who prefers shorter output could....
-     --short:: Should a person and/or program want shorter output, he
-               she/they/it can...
+     `--short`:: Use this to emit output in the short-format.
+     `--short`:: You can use this to get output in the short-format.
+     `--short`:: A user who prefers shorter output could....
+     `--short`:: Should a person and/or program want shorter output, he
+                 she/they/it can...
 
     This practice often eliminates the need to involve human actors in
     your description, but it is a good practice regardless of the
@@ -659,12 +659,12 @@ Writing Documentation:
     addressing the hypothetical user, and possibly "we" when
     discussing how the program might react to the user.  E.g.
 
-      You can use this option instead of --xyz, but we might remove
+      You can use this option instead of `--xyz`, but we might remove
       support for it in future versions.
 
     while keeping in mind that you can probably be less verbose, e.g.
 
-      Use this instead of --xyz. This option might be removed in future
+      Use this instead of `--xyz`. This option might be removed in future
       versions.
 
   - If you still need to refer to an example person that is
@@ -682,68 +682,118 @@ Writing Documentation:
  The same general rule as for code applies -- imitate the existing
  conventions.
 
- A few commented examples follow to provide reference when writing or
- modifying command usage strings and synopsis sections in the manual
- pages:
 
- Placeholders are spelled in lowercase and enclosed in angle brackets:
-   <file>
-   --sort=<key>
-   --abbrev[=<n>]
+Markup:
+
+ Literal parts (e.g. use of command-line options, command names,
+ branch names, URLs, pathnames (files and directories), configuration and
+ environment variables) must be typeset as verbatim (i.e. wrapped with
+ backticks):
+   `--pretty=oneline`
+   `git rev-list`
+   `remote.pushDefault`
+   `http://git.example.com`
+   `.git/config`
+   `GIT_DIR`
+   `HEAD`
+   `umask`(2)
+
+ An environment variable must be prefixed with "$" only when referring to its
+ value and not when referring to the variable itself, in this case there is
+ nothing to add except the backticks:
+   `GIT_DIR` is specified
+   `$GIT_DIR/hooks/pre-receive`
+
+ Word phrases enclosed in `backtick characters` are rendered literally
+ and will not be further expanded. The use of `backticks` to achieve the
+ previous rule means that literal examples should not use AsciiDoc
+ escapes.
+   Correct:
+      `--pretty=oneline`
+   Incorrect:
+      `\--pretty=oneline`
+
+ Placeholders are spelled in lowercase and enclosed in
+ angle brackets surrounded by underscores:
+   _<file>_
+   _<commit>_
 
  If a placeholder has multiple words, they are separated by dashes:
-   <new-branch-name>
-   --template=<template-directory>
+   _<new-branch-name>_
+   _<template-directory>_
+
+ A placeholder is not enclosed in backticks, as it is not a literal.
+
+ When needed, use a distinctive identifier for placeholders, usually
+ made of a qualification and a type:
+   _<git-dir>_
+   _<key-id>_
+
+ When literal and placeholders are mixed, each markup is applied for
+ each sub-entity. If they are stuck, a special markup, called
+ unconstrained formatting is required.
+ Unconstrained formating for placeholders is __<like-this>__
+ Unconstrained formatting for literal formatting is ++like this++
+   `--jobs` _<n>_
+   ++--sort=++__<key>__
+   __<directory>__++/.git++
+   ++remote.++__<name>__++.mirror++
+
+ caveat: ++ unconstrained format is not verbatim and may expand
+ content. Use Asciidoc escapes inside them.
 
- When a placeholder is cited in text paragraph, it is enclosed in angle
- brackets to remind the reader the reference in the synopsis section.
- For better visibility, the placeholder is typeset in italics:
-   The _<file>_ to be added.
+Synopsis Syntax
+
+ Syntax grammar is formatted neither as literal nor as placeholder.
+
+ 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>]
+   ++--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
@@ -754,39 +804,6 @@ Writing Documentation:
    the user would type into a shell and use 'Git' (uppercase first letter)
    when talking about the version control system and its properties.
 
- A few commented examples follow to provide reference when writing or
- modifying paragraphs or option/command explanations that contain options
- or commands:
-
- Literal examples (e.g. use of command-line options, command names,
- branch names, URLs, pathnames (files and directories), configuration and
- environment variables) must be typeset in monospace (i.e. wrapped with
- backticks):
-   `--pretty=oneline`
-   `git rev-list`
-   `remote.pushDefault`
-   `http://git.example.com`
-   `.git/config`
-   `GIT_DIR`
-   `HEAD`
-
- An environment variable must be prefixed with "$" only when referring to its
- value and not when referring to the variable itself, in this case there is
- nothing to add except the backticks:
-   `GIT_DIR` is specified
-   `$GIT_DIR/hooks/pre-receive`
-
- Word phrases enclosed in `backtick characters` are rendered literally
- and will not be further expanded. The use of `backticks` to achieve the
- previous rule means that literal examples should not use AsciiDoc
- escapes.
-   Correct:
-      `--pretty=oneline`
-   Incorrect:
-      `\--pretty=oneline`
-
-A placeholder is not enclosed in backticks, as it is not a literal.
-
  If some place in the documentation needs to typeset a command usage
  example with inline substitutions, it is fine to use +monospaced and
  inline substituted text+ instead of `monospaced literal text`, and with