t5532: use write_script

The recent cleanup in b7cbbff switched t5532's use of
backticks to $(). This matches our normal shell style, which
is good. But it also breaks the test on Solaris, where
/bin/sh does not understand $().

Our normal shell style assumes a modern-ish shell which
knows about $(). However, some tests create small helper
scripts and just write "#!/bin/sh" into them. These scripts
either need to go back to using backticks, or they need to
respect $SHELL_PATH. The easiest way to do the latter is to
use write_script.

While we're at it, let's also stick the script creation
inside a test_expect block (our usual style), and split the
perl snippet into its own script (to prevent quoting
madness).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5532-fetch-proxy.sh

@@ -12,10 +12,8 @@ test_expect_success 'setup remote repo' '
 	)
 '
 
-cat >proxy <<'EOF'
-#!/bin/sh
-echo >&2 "proxying for $*"
-cmd=$("$PERL_PATH" -e '
+test_expect_success 'setup proxy script' '
+	write_script proxy-get-cmd "$PERL_PATH" <<-\EOF &&
 	read(STDIN, $buf, 4);
 	my $n = hex($buf) - 4;
 	read(STDIN, $buf, $n);
@@ -23,11 +21,16 @@ cmd=$("$PERL_PATH" -e '
 	# drop absolute-path on repo name
 	$cmd =~ s{ /}{ };
 	print $cmd;
-')
-echo >&2 "Running '$cmd'"
-exec $cmd
-EOF
-chmod +x proxy
+	EOF
+
+	write_script proxy <<-\EOF
+	echo >&2 "proxying for $*"
+	cmd=$(./proxy-get-cmd)
+	echo >&2 "Running $cmd"
+	exec $cmd
+	EOF
+'
+
 test_expect_success 'setup local repo' '
 	git remote add fake git://example.com/remote &&
 	git config core.gitproxy ./proxy