Merge pull request #802 from spyrkob/Issue-801_remove_jgit_config_files

[#801] Replace file-based jgit configuration with in-memory one

prospero-common/src/main/java/org/wildfly/prospero/installation/git/GitStorage.java

@@ -20,6 +20,7 @@
 import org.eclipse.jgit.api.ResetCommand;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.StoredConfig;
+import org.eclipse.jgit.util.SystemReader;
 import org.wildfly.channel.Channel;
 import org.wildfly.channel.ChannelManifest;
 import org.wildfly.prospero.ProsperoLogger;
@@ -66,6 +67,12 @@ public class GitStorage implements AutoCloseable {
     private final Path base;
     private final SavedStateParser savedStateParser;
 
+    static {
+        // override the SystemReader to ignore git configuration files
+        final SystemReader systemReader = SystemReader.getInstance();
+        SystemReader.setInstance(new NonPersistingSystemReader(systemReader));
+    }
+
     public GitStorage(Path base) throws MetadataException {
         this.base = base.resolve(ProsperoMetadataUtils.METADATA_DIR);
         try {

prospero-common/src/main/java/org/wildfly/prospero/installation/git/NonPersistingSystemReader.java

@@ -0,0 +1,124 @@
+/*
+ * Copyright 2024 Red Hat, Inc. and/or its affiliates
+ * and other contributors as indicated by the @author tags.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.wildfly.prospero.installation.git;
+
+import java.io.IOException;
+
+import org.eclipse.jgit.errors.ConfigInvalidException;
+import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.StoredConfig;
+import org.eclipse.jgit.storage.file.FileBasedConfig;
+import org.eclipse.jgit.util.FS;
+import org.eclipse.jgit.util.SystemReader;
+
+/**
+ * A jgit system reader that uses default system/user/git configurations and does not persist them.
+ * <p>
+ * This avoids jgit having to create configuration files in e.g. user home. We use a limited scope of git and should
+ * be self-contained.
+ */
+class NonPersistingSystemReader extends SystemReader {
+    private final SystemReader systemReader;
+
+    public NonPersistingSystemReader(SystemReader systemReader) {
+        this.systemReader = systemReader;
+    }
+
+    @Override
+    public String getHostname() {
+        return systemReader.getHostname();
+    }
+
+    @Override
+    public String getenv(String s) {
+        return systemReader.getenv(s);
+    }
+
+    @Override
+    public String getProperty(String s) {
+        return systemReader.getProperty(s);
+    }
+
+    @Override
+    public StoredConfig getUserConfig() throws ConfigInvalidException, IOException {
+        return new NonPersistStoredConfig();
+    }
+
+    @Override
+    public StoredConfig getJGitConfig() throws ConfigInvalidException, IOException {
+        return new NonPersistStoredConfig();
+    }
+
+    @Override
+    public StoredConfig getSystemConfig() throws ConfigInvalidException, IOException {
+        return new NonPersistStoredConfig();
+    }
+
+    @Override
+    public FileBasedConfig openUserConfig(Config config, FS fs) {
+        return new EmptyFileBasedConfig(config, fs);
+    }
+
+    @Override
+    public FileBasedConfig openSystemConfig(Config config, FS fs) {
+        return new EmptyFileBasedConfig(config, fs);
+    }
+
+    @Override
+    public FileBasedConfig openJGitConfig(Config config, FS fs) {
+        return new EmptyFileBasedConfig(config, fs);
+    }
+
+    @Override
+    public long getCurrentTime() {
+        return systemReader.getCurrentTime();
+    }
+
+    @Override
+    public int getTimezone(long l) {
+        return systemReader.getTimezone(l);
+    }
+
+    private static class NonPersistStoredConfig extends StoredConfig {
+        @Override
+        public void load() throws IOException, ConfigInvalidException {
+            clear();
+        }
+
+        @Override
+        public void save() throws IOException {
+            // do nothing
+        }
+    }
+
+    private static class EmptyFileBasedConfig extends FileBasedConfig {
+        public EmptyFileBasedConfig(Config config, FS fs) {
+            super(config, null, fs);
+        }
+
+        @Override
+        public void load() throws IOException, ConfigInvalidException {
+            this.clear();
+        }
+
+        @Override
+        public void save() throws IOException {
+            // do nothing
+        }
+    }
+}