Create Differ – a simple tool for diffing branchesmain

Written mostly to help me manage the diff between various branches in
the OpenJDK repos and the BSD port repos. The idea is to simply filter
out files I don't need to spend time on, while allowing me to easily
inspect those that need it.

1 files changed, 68 insertions, 0 deletions

diff --git a/Differ.java b/Differ.java
new file mode 100644
index 0000000..b53f7fe
--- /dev/null
+++ b/Differ.java
@@ -0,0 +1,68 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2025 The FreeBSD Foundation
+ *
+ * This software was developed by Eilertsens Kodeknekkeri <haraldei@anduin.net>
+ * under sponsorship from The FreeBSD Foundation.
+ */
+
+import java.io.IOException;
+import java.io.StringWriter;
+
+public class Differ
+{
+	private String commit;
+
+	public static void main(String[] args)
+	{
+		var differ = new Differ(args);
+		differ.run();
+	}
+
+	public Differ(String[] args)
+	{
+		commit = args[0];
+	}
+
+	public void run()
+	{
+		try {
+			String[] cmd = {"git", "diff", "--stat", "--name-only", commit};
+			var p = Runtime.getRuntime().exec(cmd);
+
+			p.inputReader()
+				.lines()
+				.filter(filename -> { return includeDiff(filename); })
+				.forEach(filename -> { System.out.println("[ ] " + filename); });
+		} catch (IOException e) {
+			System.err.println("That didn't work: " + e);
+		}
+	}
+
+	private boolean includeDiff(String filename)
+	{
+		try {
+			String[] cmd = {"git", "diff", commit, "--", filename};
+			// System.out.println("[*] Running `" + String.join(" ", cmd) + "`...");
+			var p = Runtime.getRuntime().exec(cmd);
+
+			return p.inputReader()
+				.lines()
+				.anyMatch(line -> { return interestingLine(line); });
+
+		} catch (IOException e) {
+			System.err.println("Could not fetch diff: " + e);
+			return false;
+		}
+	}
+
+	private boolean interestingLine(String line)
+	{
+		var interesting = line.matches("^[+-][^+-].*") && ! line.matches("^.*Copyright.*");
+
+		// System.out.println((interesting ? "! " : "  ") + line);
+
+		return interesting;
+	}
+}