Re: [RFC] Git config file reader in Perl (WIP)

[Jakub Narebski <jnareb@gmail.com>]

Johannes Schindelin wrote:
> 
> On Fri, 19 Jan 2007, Jakub Narebski wrote:
> 
>> From a bit of testing, as documentation of config file format is 
>> woefully incomplete, (yes, I know I should use the source) _some_ of C 
>> escape sequences aka. character escape codes (CEC) are parsed:
> 
> No, you should not just use the source. You should use the source _and_ 
> complete the documentation.

Something like the patch below? Untested! ("make doc" up to 
git-repo-config.txt compiles, though).

I'm not sure how to tell that you can have [section] if you have
[section "subsection"], but you don't need to. And I probably forgot
to add some information.

And I'm not sure if some behavior should not be changed, for example
allowing _any_ line to be continued with `\`, or that other character
escape sequences and perhaps also octal character sequences should be
allowed (either that or `\b` should not be parsed).

I can send proper patch if requested, but I'd rather above issues
were resolved first.

diff --git a/Documentation/config.txt b/Documentation/config.txt
index da7fde5..9544308 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -14,14 +14,53 @@ dot-separated segment and the section name is everything before the last
 dot. The variable names are case-insensitive and only alphanumeric
 characters are allowed. Some variables may appear multiple times.
 
+Syntax
+~~~~~~
+
 The syntax is fairly flexible and permissive; whitespaces are mostly
-ignored. The '#' and ';' characters begin comments to the end of line,
-blank lines are ignored, lines containing strings enclosed in square
-brackets start sections and all the other lines are recognized
-as setting variables, in the form 'name = value'. If there is no equal
-sign on the line, the entire line is taken as 'name' and the variable
-is recognized as boolean "true". String values may be entirely or partially
-enclosed in double quotes; some variables may require special value format.
+ignored.  The '#' and ';' characters begin comments to the end of line,
+blank lines are ignored.
+
+The file consists of sections and variables.  A section begins with
+the name of the section in square brackets and continues until the next
+section begins.  Section names are not case sensitive.  Each variable
+must belong to some section, which means that there must be section
+header before first setting of a variable.
+
+Sections can be further divided into subsections.  To begin a subsection
+put it name in double quotes, separated by space from the section name,
+in the section header, like in example below
+
+	[section "subsection"]
+
+Subsection names can contain whitespace and are case sensitive.  Variables
+may belong directly to a section, or to a given subsection.
+
+All the other lines are recognized as setting variables, in the form
+'name = value'. If there is no equal sign on the line, the entire line
+is taken as 'name' and the variable is recognized as boolean "true".
+Variable names are case insensitive.  There can be more than one value
+for a given variable; we say then that variable is multivalued.
+
+Leading and trailing whitespace in a variable value is discarded.
+Internal whitespace within a variable value is retained verbatim.
+
+String values may be entirely or partially enclosed in double quotes.
+You need to enclose variable value in double quotes if you want to
+preserve leading or trailing whitespace, or if variable value contains
+beginning of comment characters, it means if it contains `#` or `;`.
+Double quote `"` and backslash `\` characters in variable value must
+be escaped: use `\"` for `"`, and `\\` for `\`.
+
+The following escape sequences (beside `\"` and `\\`) are recognized:
+`\n` for newline character (NL), `\t` for horizontal tabulation (HT, TAB)
+and `\b` for backspace (BS).  No other character escape codes, nor octal
+char sequences are valid.
+
+Variable value ending in a `\` is continued on the next line in the 
+customary UNIX fashion.
+
+Some variables may require special value format.
 
 Example
 ~~~~~~~