Don't rely on an implicit default character set

JEP 400 (Java 18) will change the default character set to UTF-8
unconditionally.[1] EGit has two places where it used the default
character set implicitly, and two where it used it explicitly.

Change all four locations to use SystemReader.getDefaultCharset(),
which gets the locale-dependent charset the way JEP 400 recommends.

[1] https://openjdk.java.net/jeps/400

Change-Id: I0d16916d2ed5a91fa27f23357dfc15306b65d132
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

3 files changed, 27 insertions, 9 deletions

diff --git a/org.eclipse.egit.core/src/org/eclipse/egit/core/internal/signing/ExternalGpgSigner.java b/org.eclipse.egit.core/src/org/eclipse/egit/core/internal/signing/ExternalGpgSigner.java
index 49790c8d08..d565d64047 100644
--- a/org.eclipse.egit.core/src/org/eclipse/egit/core/internal/signing/ExternalGpgSigner.java
+++ b/org.eclipse.egit.core/src/org/eclipse/egit/core/internal/signing/ExternalGpgSigner.java
@@ -16,7 +16,6 @@ import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
-import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.text.MessageFormat;
 import java.util.Arrays;
@@ -160,7 +159,7 @@ public class ExternalGpgSigner extends GpgSigner implements GpgObjectSigner {
 		if (b != null) {
 			try {
 				return new String(b.toByteArray(4000),
-						Charset.defaultCharset());
+						SystemReader.getInstance().getDefaultCharset());
 			} catch (IOException e) {
 				Activator.logWarning(CoreText.ExternalGpgSigner_bufferError, e);
 			}
@@ -459,7 +458,8 @@ public class ExternalGpgSigner extends GpgSigner implements GpgObjectSigner {
 						runProcess(process, null, b -> {
 							try (BufferedReader r = new BufferedReader(
 									new InputStreamReader(b.openInputStream(),
-											Charset.defaultCharset()))) {
+											SystemReader.getInstance()
+													.getDefaultCharset()))) {
 								result[0] = r.readLine();
 							}
 						}, null);
diff --git a/org.eclipse.egit.core/src/org/eclipse/egit/core/op/CreatePatchOperation.java b/org.eclipse.egit.core/src/org/eclipse/egit/core/op/CreatePatchOperation.java
index e65826a8de..2d3d522c08 100644
--- a/org.eclipse.egit.core/src/org/eclipse/egit/core/op/CreatePatchOperation.java
+++ b/org.eclipse.egit.core/src/org/eclipse/egit/core/op/CreatePatchOperation.java
@@ -59,6 +59,7 @@ import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.treewalk.FileTreeIterator;
 import org.eclipse.jgit.treewalk.filter.TreeFilter;
+import org.eclipse.jgit.util.SystemReader;
 import org.eclipse.osgi.util.NLS;
 
 /**
@@ -254,12 +255,28 @@ public class CreatePatchOperation implements IEGitOperation {
 
 	private void appendOutputStream(final StringBuilder sb,
 			final ByteArrayOutputStream outputStream) {
+		String encoding = currentEncoding != null ? currentEncoding
+				: UTF_8.name();
 		try {
-			String encoding = currentEncoding != null ? currentEncoding
-					: UTF_8.name();
 			sb.append(outputStream.toString(encoding));
 		} catch (UnsupportedEncodingException e) {
-			sb.append(outputStream.toString());
+			// Can only happen if encoding != UTF-8
+			String defaultCharset = SystemReader.getInstance()
+					.getDefaultCharset().name();
+			try {
+				if (!encoding.equals(defaultCharset)) {
+					sb.append(outputStream.toString(defaultCharset));
+					return;
+				}
+			} catch (UnsupportedEncodingException ignored) {
+				// What? The locale charset is also not known? Fall back to
+				// UTF-8.
+			}
+			try {
+				sb.append(outputStream.toString(UTF_8.name()));
+			} catch (UnsupportedEncodingException cannotOccur) {
+				// Known not to happen.
+			}
 		}
 	}
 
diff --git a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/revision/EditableRevision.java b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/revision/EditableRevision.java
index 5e66f0229c..3c36b2c4c5 100644
--- a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/revision/EditableRevision.java
+++ b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/revision/EditableRevision.java
@@ -32,6 +32,7 @@ import org.eclipse.egit.ui.Activator;
 import org.eclipse.egit.ui.internal.UIText;
 import org.eclipse.jface.resource.ImageDescriptor;
 import org.eclipse.jface.text.IDocument;
+import org.eclipse.jgit.util.SystemReader;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.team.core.history.IFileRevision;
 import org.eclipse.ui.IEditorInput;
@@ -221,10 +222,10 @@ public class EditableRevision extends FileRevisionTypedElement implements
 				try {
 					String charset = editable.getCharset();
 					if (charset == null) {
-						editable.setContent(document.get().getBytes());
-					} else {
-						editable.setContent(document.get().getBytes(charset));
+						charset = SystemReader.getInstance().getDefaultCharset()
+								.name();
 					}
+					editable.setContent(document.get().getBytes(charset));
 					// We _know_ that the document provider _cannot_ really save
 					// the IStorage. Nevertheless calling its save operation is
 					// necessary because otherwise an internal "modified" flag