Improve warning message with no digest found

Currently the message only mentions the artifact to download but not
where it originates from, this makes it very hard to analyze and fix the
issue (actually one needs to to run a debugger).

This enhances the message a tiny little bit to mention the artifact
descriptors repository URL.

bundles/org.eclipse.equinox.p2.artifact.repository/src/org/eclipse/equinox/internal/p2/artifact/repository/RawMirrorRequest.java

@@ -94,7 +94,8 @@ protected IStatus getArtifact(IArtifactDescriptor artifactDescriptor, OutputStre
 					IArtifactDescriptor.DOWNLOAD_CHECKSUM, Collections.emptySet());
 			if (steps.isEmpty()) {
 				LogHelper.log(new Status(IStatus.WARNING, Activator.ID,
-						NLS.bind(Messages.noDigestAlgorithmToVerifyDownload, artifactDescriptor.getArtifactKey())));
+						NLS.bind(Messages.noDigestAlgorithmToVerifyDownload, artifactDescriptor.getArtifactKey(),
+								artifactDescriptor.getRepository().getLocation())));
 			}
 			ProcessingStep[] stepArray = steps.toArray(new ProcessingStep[steps.size()]);
 			// TODO should probably be using createAndLink here

bundles/org.eclipse.equinox.p2.artifact.repository/src/org/eclipse/equinox/internal/p2/artifact/repository/messages.properties

@@ -66,4 +66,4 @@ retryRequest=Download of {0} failed on repository {1}. Retrying.
 error_copying_local_file=An error occurred copying file {0}.
 
 onlyInsecureDigestAlgorithmUsed = The digest algorithms ({0}) used to verify {1} have severely compromised security. Please report this concern to the artifact provider.
-noDigestAlgorithmToVerifyDownload = No digest algorithm is available to verify download of {0}.
+noDigestAlgorithmToVerifyDownload = No digest algorithm is available to verify download of {0} from repository {1}.

bundles/org.eclipse.equinox.p2.artifact.repository/src/org/eclipse/equinox/internal/p2/artifact/repository/simple/SimpleArtifactRepository.java

@@ -491,7 +491,8 @@ private OutputStream addPreSteps(ProcessingStepHandler handler, IArtifactDescrip
 		addChecksumVerifiers(descriptor, downloadChecksumSteps, skipChecksums, IArtifactDescriptor.DOWNLOAD_CHECKSUM);
 		if (downloadChecksumSteps.isEmpty() && !isLocal()) {
 			LogHelper.log(new Status(IStatus.WARNING, Activator.ID,
-					NLS.bind(Messages.noDigestAlgorithmToVerifyDownload, descriptor.getArtifactKey())));
+					NLS.bind(Messages.noDigestAlgorithmToVerifyDownload, descriptor.getArtifactKey(),
+							descriptor.getRepository().getLocation())));
 		}
 		steps.addAll(downloadChecksumSteps);