t5516/t5601: avoid using localhost for failing HTTPS requests

In 6dcbdc0 (remote: create fetch.credentialsInUrl config,
2022-06-06), we added four test cases that validate various behavior
around passing credentials as part of the URL (which is considered
unsafe in general).

These tests do not _actually_ try to connect anywhere, but have to use
the https:// protocol in order to validate the intended code paths.

However, using `localhost` for such a connection causes several
problems:

- There might be a web server running on localhost, and we do not
  actually want to connect to that.

- The DNS resolver, or the local firewall, might take a substantial
  amount of time (or forever, whichever comes first) to fail to connect,
  slowing down the test cases unnecessarily.

Let's instead use an IPv4 address that is guaranteed never to offer a
web server: 224.0.0.1 (which is part of the IP multicast range).

Incidentally, this seems to fix an issue where the tests fail in the
Windows jobs of Git's CI builds.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

t/t5516-fetch-push.sh

@@ -1854,32 +1854,32 @@ test_expect_success 'refuse to push a hidden ref, and make sure do not pollute t
 '
 
 test_expect_success LIBCURL 'fetch warns or fails when using username:password' '
-	message="URL '\''https://username:<redacted>@localhost/'\'' uses plaintext credentials" &&
-	test_must_fail git -c transfer.credentialsInUrl=allow fetch https://username:password@localhost 2>err &&
+	message="URL '\''https://username:<redacted>@224.0.0.1/'\'' uses plaintext credentials" &&
+	test_must_fail git -c transfer.credentialsInUrl=allow fetch https://username:password@224.0.0.1 2>err &&
 	! grep "$message" err &&
 
-	test_must_fail git -c transfer.credentialsInUrl=warn fetch https://username:password@localhost 2>err &&
+	test_must_fail git -c transfer.credentialsInUrl=warn fetch https://username:password@224.0.0.1 2>err &&
 	grep "warning: $message" err >warnings &&
 	test_line_count = 3 warnings &&
 
-	test_must_fail git -c transfer.credentialsInUrl=die fetch https://username:password@localhost 2>err &&
+	test_must_fail git -c transfer.credentialsInUrl=die fetch https://username:password@224.0.0.1 2>err &&
 	grep "fatal: $message" err >warnings &&
 	test_line_count = 1 warnings &&
 
-	test_must_fail git -c transfer.credentialsInUrl=die fetch https://username:@localhost 2>err &&
+	test_must_fail git -c transfer.credentialsInUrl=die fetch https://username:@224.0.0.1 2>err &&
 	grep "fatal: $message" err >warnings &&
 	test_line_count = 1 warnings
 '
 
 
 test_expect_success LIBCURL 'push warns or fails when using username:password' '
-	message="URL '\''https://username:<redacted>@localhost/'\'' uses plaintext credentials" &&
-	test_must_fail git -c transfer.credentialsInUrl=allow push https://username:password@localhost 2>err &&
+	message="URL '\''https://username:<redacted>@224.0.0.1/'\'' uses plaintext credentials" &&
+	test_must_fail git -c transfer.credentialsInUrl=allow push https://username:password@224.0.0.1 2>err &&
 	! grep "$message" err &&
 
-	test_must_fail git -c transfer.credentialsInUrl=warn push https://username:password@localhost 2>err &&
+	test_must_fail git -c transfer.credentialsInUrl=warn push https://username:password@224.0.0.1 2>err &&
 	grep "warning: $message" err >warnings &&
-	test_must_fail git -c transfer.credentialsInUrl=die push https://username:password@localhost 2>err &&
+	test_must_fail git -c transfer.credentialsInUrl=die push https://username:password@224.0.0.1 2>err &&
 	grep "fatal: $message" err >warnings &&
 	test_line_count = 1 warnings
 '

t/t5601-clone.sh

@@ -72,19 +72,19 @@ test_expect_success 'clone respects GIT_WORK_TREE' '
 '
 
 test_expect_success LIBCURL 'clone warns or fails when using username:password' '
-	message="URL '\''https://username:<redacted>@localhost/'\'' uses plaintext credentials" &&
-	test_must_fail git -c transfer.credentialsInUrl=allow clone https://username:password@localhost attempt1 2>err &&
+	message="URL '\''https://username:<redacted>@224.0.0.1/'\'' uses plaintext credentials" &&
+	test_must_fail git -c transfer.credentialsInUrl=allow clone https://username:password@224.0.0.1 attempt1 2>err &&
 	! grep "$message" err &&
 
-	test_must_fail git -c transfer.credentialsInUrl=warn clone https://username:password@localhost attempt2 2>err &&
+	test_must_fail git -c transfer.credentialsInUrl=warn clone https://username:password@224.0.0.1 attempt2 2>err &&
 	grep "warning: $message" err >warnings &&
 	test_line_count = 2 warnings &&
 
-	test_must_fail git -c transfer.credentialsInUrl=die clone https://username:password@localhost attempt3 2>err &&
+	test_must_fail git -c transfer.credentialsInUrl=die clone https://username:password@224.0.0.1 attempt3 2>err &&
 	grep "fatal: $message" err >warnings &&
 	test_line_count = 1 warnings &&
 
-	test_must_fail git -c transfer.credentialsInUrl=die clone https://username:@localhost attempt3 2>err &&
+	test_must_fail git -c transfer.credentialsInUrl=die clone https://username:@224.0.0.1 attempt3 2>err &&
 	grep "fatal: $message" err >warnings &&
 	test_line_count = 1 warnings
 '