Add test case for $Id$ expanded in the repository

This test case would have caught the bug fixed by revision
c23290d.

It puts various forms of $Id$ into a file in the repository,
without allowing git to collapse them to uniformity.  Then enables the
$Id$ expansion on checkout, and checks that what is checked out has
coped with the various forms.

Signed-off-by: Andy Parkins <andyparkins@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

t/t0021-conversion.sh

@@ -45,4 +45,40 @@ test_expect_success check '
 	test "z$id" = "z$embedded"
 '
 
+# If an expanded ident ever gets into the repository, we want to make sure that
+# it is collapsed before being expanded again on checkout
+test_expect_success expanded_in_repo '
+	{
+		echo "File with expanded keywords"
+		echo "\$Id\$"
+		echo "\$Id:\$"
+		echo "\$Id: 0000000000000000000000000000000000000000 \$"
+		echo "\$Id: NoSpaceAtEnd\$"
+		echo "\$Id:NoSpaceAtFront \$"
+		echo "\$Id:NoSpaceAtEitherEnd\$"
+		echo "\$Id: NoTerminatingSymbol"
+	} > expanded-keywords &&
+
+	{
+		echo "File with expanded keywords"
+		echo "\$Id: 4f21723e7b15065df7de95bd46c8ba6fb1818f4c \$"
+		echo "\$Id: 4f21723e7b15065df7de95bd46c8ba6fb1818f4c \$"
+		echo "\$Id: 4f21723e7b15065df7de95bd46c8ba6fb1818f4c \$"
+		echo "\$Id: 4f21723e7b15065df7de95bd46c8ba6fb1818f4c \$"
+		echo "\$Id: 4f21723e7b15065df7de95bd46c8ba6fb1818f4c \$"
+		echo "\$Id: 4f21723e7b15065df7de95bd46c8ba6fb1818f4c \$"
+		echo "\$Id: NoTerminatingSymbol"
+	} > expected-output &&
+
+	git add expanded-keywords &&
+	git commit -m "File with keywords expanded" &&
+
+	echo "expanded-keywords ident" >> .gitattributes &&
+
+	rm -f expanded-keywords &&
+	git checkout -- expanded-keywords &&
+	cat expanded-keywords &&
+	cmp expanded-keywords expected-output
+'
+
 test_done