Use {web,instaweb,help}.browser config options.

Now "git-instaweb" will try to use the browser configured as
"web.browser", if "instaweb.browser" is not set.

"git-browse-help" will check first "help.browser" and then
"web.browser".
Signed-off-by: NChristian Couder <chriscool@tuxfamily.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

git-browse-help.sh

@@ -70,9 +70,13 @@ do
 done
 
 if test -z "$browser"; then
-    browser=`git config web.browser`
+    for opt in "help.browser" "web.browser"
+    do
+	browser="`git config $opt`"
+	test -z "$browser" || break
+    done
     if test -n "$browser" && ! valid_tool "$browser"; then
-	    echo >&2 "git config option web.browser set to unknown browser: $browser"
+	    echo >&2 "git config option $opt set to unknown browser: $browser"
 	    echo >&2 "Resetting to default..."
 	    unset browser
     fi

git-instaweb.sh

@@ -24,6 +24,7 @@ fqgitdir="$GIT_DIR"
 local="`git config --bool --get instaweb.local`"
 httpd="`git config --get instaweb.httpd`"
 browser="`git config --get instaweb.browser`"
+test -z "$browser" && browser="`git config --get web.browser`"
 port=`git config --get instaweb.port`
 module_path="`git config --get instaweb.modulepath`"