Fix git-instaweb breakage on MacOS X due to the limited sed functionality

git-instaweb relied on a pipe in a sed script, but this is not supported
by MacOS X sed when using BREs.  git-instaweb relies on a working perl
in any case, and perl re are more consistent between platforms, so
replace sed invocation with an equivalent perl invocation.

Also, fix the documented -b "" to work without giving a spurious 'command
not found' error.

Signed-off-by: Charles Bailey <charles@hashpling.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -880,6 +880,7 @@ git-instaweb: git-instaweb.sh gitweb/gitweb.cgi gitweb/gitweb.css
 	    -e '/@@GITWEB_CGI@@/d' \
 	    -e '/@@GITWEB_CSS@@/r gitweb/gitweb.css' \
 	    -e '/@@GITWEB_CSS@@/d' \
+	    -e 's|@@PERL@@|$(PERL_PATH_SQ)|g' \
 	    $@.sh > $@+ && \
 	chmod +x $@+ && \
 	mv $@+ $@

git-instaweb.sh

@@ -3,6 +3,7 @@
 # Copyright (c) 2006 Eric Wong
 #
 
+PERL='@@PERL@@'
 OPTIONS_KEEPDASHDASH=
 OPTIONS_SPEC="\
 git-instaweb [options] (--start | --stop | --restart)
@@ -232,16 +233,18 @@ EOF
 }
 
 script='
-s#^\(my\|our\) $projectroot =.*#\1 $projectroot = "'$(dirname "$fqgitdir")'";#
-s#\(my\|our\) $gitbin =.*#\1 $gitbin = "'$GIT_EXEC_PATH'";#
-s#\(my\|our\) $projects_list =.*#\1 $projects_list = $projectroot;#
-s#\(my\|our\) $git_temp =.*#\1 $git_temp = "'$fqgitdir/gitweb/tmp'";#'
+s#^(my|our) \$projectroot =.*#$1 \$projectroot = "'$(dirname "$fqgitdir")'";#;
+s#(my|our) \$gitbin =.*#$1 \$gitbin = "'$GIT_EXEC_PATH'";#;
+s#(my|our) \$projects_list =.*#$1 \$projects_list = \$projectroot;#;
+s#(my|our) \$git_temp =.*#$1 \$git_temp = "'$fqgitdir/gitweb/tmp'";#;'
 
 gitweb_cgi () {
 	cat > "$1.tmp" <<\EOFGITWEB
 @@GITWEB_CGI@@
 EOFGITWEB
-	sed "$script" "$1.tmp"  > "$1"
+	# Use the configured full path to perl to match the generated
+	# scripts' 'hashpling' line
+	"$PERL" -p -e "$script" "$1.tmp"  > "$1"
 	chmod +x "$1"
 	rm -f "$1.tmp"
 }
@@ -273,4 +276,4 @@ esac
 
 start_httpd
 url=http://127.0.0.1:$port
-"$browser" $url || echo $url
+test -n "$browser" && "$browser" $url || echo $url