Valgrind support: check for more than just programming errors

This patch makes --valgrind try to override _all_ Git binaries in the
PATH, and it makes it an error to call *.sh and *.perl scripts directly.

While it is not strictly necessary to look through the whole PATH to
find git binaries to override, it is in line with running an expensive
test (which valgrind is) to make extra sure that only binaries are
tested that actually come from the git.git checkout.

In the same spirit, we can test that neither our test suite nor our
scripts try to run the *.sh or *.perl scripts directly.

It's more like a "because we can" than a "this is tightly connected
to valgrind", but in the author's opinion "because we can" is "so we
should" in this case.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/test-lib.sh

@@ -531,6 +531,10 @@ else
 		then
 			symlink_target=../valgrind.sh
 		fi
+		case "$base" in
+		*.sh|*.perl)
+			symlink_target=../unprocessed-script
+		esac
 		# create the link, or replace it if it is out of date
 		make_symlink "$symlink_target" "$GIT_VALGRIND/bin/$base" || exit
 	}
@@ -542,6 +546,17 @@ else
 	do
 		make_valgrind_symlink $file
 	done
+	OLDIFS=$IFS
+	IFS=:
+	for path in $PATH
+	do
+		ls "$path"/git-* 2> /dev/null |
+		while read file
+		do
+			make_valgrind_symlink "$file"
+		done
+	done
+	IFS=$OLDIFS
 	PATH=$GIT_VALGRIND/bin:$PATH
 	GIT_EXEC_PATH=$GIT_VALGRIND/bin
 	export GIT_VALGRIND