Implement file lock for git (#1838)

Adds a "file lock" command that can be used to mark files as locked by a specific user. This command is implemented for git using a store to keep the locks.

Additionally, the Git LFS locking API is implemented.

To display locks, the scm-manager/scm-file-lock-plugin can be used.

Co-authored-by: Eduard Heimbuch <eduard.heimbuch@cloudogu.com>

scm-test/src/main/java/sonia/scm/web/BufferedServletInputStream.java

@@ -0,0 +1,59 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020-present Cloudogu GmbH and Contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package sonia.scm.web;
+
+import javax.servlet.ReadListener;
+import javax.servlet.ServletInputStream;
+import java.io.ByteArrayInputStream;
+import java.nio.charset.StandardCharsets;
+
+public class BufferedServletInputStream extends ServletInputStream {
+
+  private ByteArrayInputStream input;
+
+  BufferedServletInputStream(String content) {
+    this.input = new ByteArrayInputStream(content.getBytes(StandardCharsets.US_ASCII));
+  }
+
+  @Override
+  public int read() {
+    return input.read();
+  }
+
+  @Override
+  public boolean isFinished() {
+    return false;
+  }
+
+  @Override
+  public boolean isReady() {
+    return true;
+  }
+
+  @Override
+  public void setReadListener(ReadListener readListener) {
+    // not necessary for tests
+  }
+}