Don't handle internal git errors as an HTTP error

The fix that fixed the propagation of error-codes:
  8984e1f66 HTTP Smart: set correct HTTP status on error [1]
made some faulty assumptions.

"Wants not valid", can be an intermittent git error and the HTTP
response should be 200 and not 400 since the request isn't necessary
faulty.

[1] https://git.eclipse.org/r/c/jgit/jgit/+/192677

Bug: 579676
Change-Id: I461bc78ff6e450636811ece50d21c57a2a7f2ae3

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java

diff --git a/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java b/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java
index 23a398f..509ea4c 100644
--- a/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java
+++ b/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java
@@ -10,9 +10,9 @@
 
 package org.eclipse.jgit.http.server;
 
-import static javax.servlet.http.HttpServletResponse.SC_BAD_REQUEST;
 import static javax.servlet.http.HttpServletResponse.SC_FORBIDDEN;
 import static javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
+import static javax.servlet.http.HttpServletResponse.SC_OK;
 import static javax.servlet.http.HttpServletResponse.SC_UNAUTHORIZED;
 import static javax.servlet.http.HttpServletResponse.SC_UNSUPPORTED_MEDIA_TYPE;
 import static org.eclipse.jgit.http.server.GitSmartHttpTools.UPLOAD_PACK;
@@ -49,7 +49,6 @@
 import org.eclipse.jgit.transport.ServiceMayNotContinueException;
 import org.eclipse.jgit.transport.UploadPack;
 import org.eclipse.jgit.transport.UploadPackInternalServerErrorException;
-import org.eclipse.jgit.transport.WantNotValidException;
 import org.eclipse.jgit.transport.resolver.ServiceNotAuthorizedException;
 import org.eclipse.jgit.transport.resolver.ServiceNotEnabledException;
 import org.eclipse.jgit.transport.resolver.UploadPackFactory;
@@ -157,8 +156,9 @@ private static int statusCodeForThrowable(Throwable error) {
 		if (error instanceof ServiceNotEnabledException) {
 			return SC_FORBIDDEN;
 		}
-		if (error instanceof WantNotValidException) {
-			return SC_BAD_REQUEST;
+		if (error instanceof PackProtocolException) {
+			// Internal git errors is not an error from an HTTP standpoint.
+			return SC_OK;
 		}
 		return SC_INTERNAL_SERVER_ERROR;
 	}

org.eclipse.jgit.http.test/tst/org/eclipse/jgit/http/test/SmartClientSmartServerTest.java

diff --git a/org.eclipse.jgit.http.test/tst/org/eclipse/jgit/http/test/SmartClientSmartServerTest.java b/org.eclipse.jgit.http.test/tst/org/eclipse/jgit/http/test/SmartClientSmartServerTest.java
index 8f3888e..b9b10b4 100644
--- a/org.eclipse.jgit.http.test/tst/org/eclipse/jgit/http/test/SmartClientSmartServerTest.java
+++ b/org.eclipse.jgit.http.test/tst/org/eclipse/jgit/http/test/SmartClientSmartServerTest.java
@@ -537,9 +537,9 @@ public void testFetchBySHA1Unreachable() throws Exception {
 							Collections.singletonList(
 									new RefSpec(unreachableCommit.name()))));
 			assertTrue(e.getMessage().contains(
-					"Bad Request"));
+					"want " + unreachableCommit.name() + " not valid"));
 		}
-		assertLastRequestStatusCode(400);
+		assertLastRequestStatusCode(200);
 	}
 
 	@Test
@@ -560,9 +560,9 @@ protected Map<String, Ref> getAdvertisedRefs(Repository repository,
 					() -> t.fetch(NullProgressMonitor.INSTANCE,
 							Collections.singletonList(new RefSpec(A.name()))));
 			assertTrue(
-					e.getMessage().contains("Bad Request"));
+					e.getMessage().contains("want " + A.name() + " not valid"));
 		}
-		assertLastRequestStatusCode(400);
+		assertLastRequestStatusCode(200);
 	}
 
 	@Test
@@ -1610,9 +1610,9 @@ public void testInvalidWant() throws Exception {
 			fail("Server accepted want " + id.name());
 		} catch (TransportException err) {
 			assertTrue(err.getMessage()
-					.contains("Bad Request"));
+					.contains("want " + id.name() + " not valid"));
 		}
-		assertLastRequestStatusCode(400);
+		assertLastRequestStatusCode(200);
 	}
 
 	@Test