Documentation fixes in git-config

Variable names must start with an alphabetic character, regexp config key
matching has its limits, sentence grammar.
Signed-off-by: NLibor Pechacek <lpechacek@suse.cz>
Acked-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -12,8 +12,9 @@ The configuration variables are used by both the git plumbing
 and the porcelains. The variables are divided into sections, wherein
 the fully qualified variable name of the variable itself is the last
 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.
+dot. The variable names are case-insensitive, allow only alphanumeric
+characters and `-`, and must start with an alphabetic character.  Some
+variables may appear multiple times.
 
 Syntax
 ~~~~~~
@@ -54,9 +55,10 @@ All the other lines (and the remainder of the line after the section
 header) 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".
-The variable names are case-insensitive and only alphanumeric
-characters and `-` are allowed.  There can be more than one value
-for a given variable; we say then that variable is multivalued.
+The variable names are case-insensitive, allow only alphanumeric characters
+and `-`, and must start with an alphabetic character.  There can be more
+than one value for a given variable; we say then that the variable is
+multivalued.
 
 Leading and trailing whitespace in a variable value is discarded.
 Internal whitespace within a variable value is retained verbatim.

Documentation/git-config.txt

@@ -85,8 +85,11 @@ OPTIONS
 	is not exactly one.
 
 --get-regexp::
-	Like --get-all, but interprets the name as a regular expression.
-	Also outputs the key names.
+	Like --get-all, but interprets the name as a regular expression and
+	writes out the key names.  Regular expression matching is currently
+	case-sensitive and done against a canonicalized version of the key
+	in which section and variable names are lowercased, but subsection
+	names are not.
 
 --global::
 	For writing options: write to global ~/.gitconfig file rather than