git-web--browse.sh: use the $( ... ) construct for command substitution

The Git CodingGuidelines prefer the $(...) construct for command
substitution instead of using the backquotes `...`.

The backquoted form is the traditional method for command
substitution, and is supported by POSIX.  However, all but the
simplest uses become complicated quickly.  In particular, embedded
command substitutions and/or the use of double quotes require
careful escaping with the backslash character.

The patch was generated by:

for _f in $(find . -name "*.sh")
do
   sed -i 's@`\(.*\)`@$(\1)@g' ${_f}
done

and then carefully proof-read.

Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>
Reviewed-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-web--browse.sh

@@ -59,7 +59,7 @@ do
 	-b|--browser*|-t|--tool*)
 		case "$#,$1" in
 		*,*=*)
-			browser=`expr "z$1" : 'z-[^=]*=\(.*\)'`
+			browser=$(expr "z$1" : 'z-[^=]*=\(.*\)')
 			;;
 		1,*)
 			usage ;;
@@ -71,7 +71,7 @@ do
 	-c|--config*)
 		case "$#,$1" in
 		*,*=*)
-			conf=`expr "z$1" : 'z-[^=]*=\(.*\)'`
+			conf=$(expr "z$1" : 'z-[^=]*=\(.*\)')
 			;;
 		1,*)
 			usage ;;
@@ -100,7 +100,7 @@ then
 	for opt in "$conf" "web.browser"
 	do
 		test -z "$opt" && continue
-		browser="`git config $opt`"
+		browser="$(git config $opt)"
 		test -z "$browser" || break
 	done
 	if test -n "$browser" && ! valid_tool "$browser"; then