Add command line support for "git difftool"

see: http://git-scm.com/docs/git-difftool

* add command line support for "jgit difftool"
* show supported commands with "jgit difftool --help"
* added "git difftool --tool-help" to show the tools (empty now)
* prepare for all other commands

Bug: 356832
Change-Id: Ice0c13ef7953a20feaf25e7746d62b94ff4e89e5
Signed-off-by: Andre Bossert <andre.bossert@siemens.com>
Signed-off-by: Simeon Andreev <simeon.danailov.andreev@gmail.com>

2 files changed, 196 insertions, 0 deletions

diff --git a/org.eclipse.jgit.pgm.test/META-INF/MANIFEST.MF b/org.eclipse.jgit.pgm.test/META-INF/MANIFEST.MF
index 2c53da8c8f..3e0a4eaf20 100644
--- a/org.eclipse.jgit.pgm.test/META-INF/MANIFEST.MF
+++ b/org.eclipse.jgit.pgm.test/META-INF/MANIFEST.MF
@@ -15,6 +15,7 @@ Import-Package: org.eclipse.jgit.api;version="[6.1.0,6.2.0)",
  org.eclipse.jgit.internal.storage.file;version="6.1.0",
  org.eclipse.jgit.junit;version="[6.1.0,6.2.0)",
  org.eclipse.jgit.lib;version="[6.1.0,6.2.0)",
+ org.eclipse.jgit.lib.internal;version="[6.1.0,6.2.0)",
  org.eclipse.jgit.merge;version="[6.1.0,6.2.0)",
  org.eclipse.jgit.pgm;version="[6.1.0,6.2.0)",
  org.eclipse.jgit.pgm.internal;version="[6.1.0,6.2.0)",
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/DiffToolTest.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/DiffToolTest.java
new file mode 100644
index 0000000000..2ce50c7827
--- /dev/null
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/DiffToolTest.java
@@ -0,0 +1,195 @@
+/*
+ * Copyright (C) 2021, Simeon Andreev <simeon.danailov.andreev@gmail.com> and others.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.pgm;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.diff.DiffEntry;
+import org.eclipse.jgit.lib.CLIRepositoryTestCase;
+import org.eclipse.jgit.pgm.opt.CmdLineParser;
+import org.eclipse.jgit.pgm.opt.SubcommandHandler;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.treewalk.FileTreeIterator;
+import org.eclipse.jgit.treewalk.TreeWalk;
+import org.junit.Before;
+import org.junit.Test;
+import org.kohsuke.args4j.Argument;
+
+/**
+ * Testing the {@code difftool} command.
+ */
+public class DiffToolTest extends CLIRepositoryTestCase {
+	public static class GitCliJGitWrapperParser {
+		@Argument(index = 0, metaVar = "metaVar_command", required = true, handler = SubcommandHandler.class)
+		TextBuiltin subcommand;
+
+		@Argument(index = 1, metaVar = "metaVar_arg")
+		List<String> arguments = new ArrayList<>();
+	}
+
+	private String[] runAndCaptureUsingInitRaw(String... args)
+			throws Exception {
+		CLIGitCommand.Result result = new CLIGitCommand.Result();
+
+		GitCliJGitWrapperParser bean = new GitCliJGitWrapperParser();
+		CmdLineParser clp = new CmdLineParser(bean);
+		clp.parseArgument(args);
+
+		TextBuiltin cmd = bean.subcommand;
+		cmd.initRaw(db, null, null, result.out, result.err);
+		cmd.execute(bean.arguments.toArray(new String[bean.arguments.size()]));
+		if (cmd.getOutputWriter() != null) {
+			cmd.getOutputWriter().flush();
+		}
+		if (cmd.getErrorWriter() != null) {
+			cmd.getErrorWriter().flush();
+		}
+		return result.outLines().toArray(new String[0]);
+	}
+
+	private Git git;
+
+	@Override
+	@Before
+	public void setUp() throws Exception {
+		super.setUp();
+		git = new Git(db);
+		git.commit().setMessage("initial commit").call();
+	}
+
+	@Test
+	public void testTool() throws Exception {
+		RevCommit commit = createUnstagedChanges();
+		List<DiffEntry> changes = getRepositoryChanges(commit);
+		String[] expectedOutput = getExpectedDiffToolOutput(changes);
+
+		String[] options = {
+				"--tool",
+				"-t",
+		};
+
+		for (String option : options) {
+			assertArrayOfLinesEquals("Incorrect output for option: " + option,
+					expectedOutput,
+					runAndCaptureUsingInitRaw("difftool", option,
+							"some_tool"));
+		}
+	}
+
+	@Test
+	public void testToolTrustExitCode() throws Exception {
+		RevCommit commit = createUnstagedChanges();
+		List<DiffEntry> changes = getRepositoryChanges(commit);
+		String[] expectedOutput = getExpectedDiffToolOutput(changes);
+
+		String[] options = { "--tool", "-t", };
+
+		for (String option : options) {
+			assertArrayOfLinesEquals("Incorrect output for option: " + option,
+					expectedOutput, runAndCaptureUsingInitRaw("difftool",
+							"--trust-exit-code", option, "some_tool"));
+		}
+	}
+
+	@Test
+	public void testToolNoGuiNoPromptNoTrustExitcode() throws Exception {
+		RevCommit commit = createUnstagedChanges();
+		List<DiffEntry> changes = getRepositoryChanges(commit);
+		String[] expectedOutput = getExpectedDiffToolOutput(changes);
+
+		String[] options = { "--tool", "-t", };
+
+		for (String option : options) {
+			assertArrayOfLinesEquals("Incorrect output for option: " + option,
+					expectedOutput, runAndCaptureUsingInitRaw("difftool",
+							"--no-gui", "--no-prompt", "--no-trust-exit-code",
+							option, "some_tool"));
+		}
+	}
+
+	@Test
+	public void testToolCached() throws Exception {
+		RevCommit commit = createStagedChanges();
+		List<DiffEntry> changes = getRepositoryChanges(commit);
+		String[] expectedOutput = getExpectedDiffToolOutput(changes);
+
+		String[] options = { "--cached", "--staged", };
+
+		for (String option : options) {
+			assertArrayOfLinesEquals("Incorrect output for option: " + option,
+					expectedOutput, runAndCaptureUsingInitRaw("difftool",
+							option, "--tool", "some_tool"));
+		}
+	}
+
+	@Test
+	public void testToolHelp() throws Exception {
+		String[] expectedOutput = {
+				"git difftool --tool=<tool> may be set to one of the following:",
+				"user-defined:",
+				"The following tools are valid, but not currently available:",
+				"Some of the tools listed above only work in a windowed",
+				"environment. If run in a terminal-only session, they will fail.", };
+
+		String option = "--tool-help";
+		assertArrayOfLinesEquals("Incorrect output for option: " + option,
+				expectedOutput, runAndCaptureUsingInitRaw("difftool", option));
+	}
+
+	private RevCommit createUnstagedChanges() throws Exception {
+		writeTrashFile("a", "Hello world a");
+		writeTrashFile("b", "Hello world b");
+		git.add().addFilepattern(".").call();
+		RevCommit commit = git.commit().setMessage("files a & b").call();
+		writeTrashFile("a", "New Hello world a");
+		writeTrashFile("b", "New Hello world b");
+		return commit;
+	}
+
+	private RevCommit createStagedChanges() throws Exception {
+		RevCommit commit = createUnstagedChanges();
+		git.add().addFilepattern(".").call();
+		return commit;
+	}
+
+	private List<DiffEntry> getRepositoryChanges(RevCommit commit)
+			throws Exception {
+		TreeWalk tw = new TreeWalk(db);
+		tw.addTree(commit.getTree());
+		FileTreeIterator modifiedTree = new FileTreeIterator(db);
+		tw.addTree(modifiedTree);
+		List<DiffEntry> changes = DiffEntry.scan(tw);
+		return changes;
+	}
+
+	private String[] getExpectedDiffToolOutput(List<DiffEntry> changes) {
+		String[] expectedToolOutput = new String[changes.size()];
+		for (int i = 0; i < changes.size(); ++i) {
+			DiffEntry change = changes.get(i);
+			String newPath = change.getNewPath();
+			String oldPath = change.getOldPath();
+			String newIdName = change.getNewId().name();
+			String oldIdName = change.getOldId().name();
+			String expectedLine = "M\t" + newPath + " (" + newIdName + ")"
+					+ "\t" + oldPath + " (" + oldIdName + ")";
+			expectedToolOutput[i] = expectedLine;
+		}
+		return expectedToolOutput;
+	}
+
+	private static void assertArrayOfLinesEquals(String failMessage,
+			String[] expected, String[] actual) {
+		assertEquals(failMessage, toString(expected), toString(actual));
+	}
+}