Add command line support for "git mergetool"

see: https://git-scm.com/docs/git-mergetool
see: https://git-scm.com/docs/git-config

* add command line support for "git mergetool"
  * add option handling for "--tool-help", "--tool=<mytool>",
"--[no-]prompt",  "--[no-]gui"
  * handle prompt
  * add MergeTools
  * add pre-defined mergetools
  * print merge actions --> no execute, will be done later

Bug: 356832
Change-Id: I6e505ffc3d03f75ecf4bba452a25d25dfcf5793f
Signed-off-by: Andre Bossert <andre.bossert@siemens.com>

3 files changed, 287 insertions, 91 deletions

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
index e2ff189276..017a5d994f 100644
--- 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
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2021, Simeon Andreev <simeon.danailov.andreev@gmail.com> and others.
+ * Copyright (C) 2021-2022, 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
@@ -14,68 +14,30 @@ import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_DIFF_SECTION;
 import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_CMD;
 import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_PROMPT;
 import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_TOOL;
-import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
-import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.diff.DiffEntry;
 import org.eclipse.jgit.internal.diffmergetool.CommandLineDiffTool;
-import org.eclipse.jgit.lib.CLIRepositoryTestCase;
 import org.eclipse.jgit.lib.StoredConfig;
-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;
+public class DiffToolTest extends ExternalToolTestCase {
 
-		@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 static final String TOOL_NAME = "some_tool";
-	private Git git;
+	private static final String DIFF_TOOL = CONFIG_DIFFTOOL_SECTION;
 
 	@Override
 	@Before
 	public void setUp() throws Exception {
 		super.setUp();
-		git = new Git(db);
-		git.commit().setMessage("initial commit").call();
 		configureEchoTool(TOOL_NAME);
 	}
 
@@ -83,7 +45,7 @@ public class DiffToolTest extends CLIRepositoryTestCase {
 	public void testNotDefinedTool() throws Exception {
 		createUnstagedChanges();
 
-		runAndCaptureUsingInitRaw("difftool", "--tool", "undefined");
+		runAndCaptureUsingInitRaw(DIFF_TOOL, "--tool", "undefined");
 		fail("Expected exception when trying to run undefined tool");
 	}
 
@@ -91,7 +53,7 @@ public class DiffToolTest extends CLIRepositoryTestCase {
 	public void testTool() throws Exception {
 		RevCommit commit = createUnstagedChanges();
 		List<DiffEntry> changes = getRepositoryChanges(commit);
-		String[] expectedOutput = getExpectedDiffToolOutput(changes);
+		String[] expectedOutput = getExpectedToolOutput(changes);
 
 		String[] options = {
 				"--tool",
@@ -101,7 +63,7 @@ public class DiffToolTest extends CLIRepositoryTestCase {
 		for (String option : options) {
 			assertArrayOfLinesEquals("Incorrect output for option: " + option,
 					expectedOutput,
-					runAndCaptureUsingInitRaw("difftool", option,
+					runAndCaptureUsingInitRaw(DIFF_TOOL, option,
 							TOOL_NAME));
 		}
 	}
@@ -110,13 +72,13 @@ public class DiffToolTest extends CLIRepositoryTestCase {
 	public void testToolTrustExitCode() throws Exception {
 		RevCommit commit = createUnstagedChanges();
 		List<DiffEntry> changes = getRepositoryChanges(commit);
-		String[] expectedOutput = getExpectedDiffToolOutput(changes);
+		String[] expectedOutput = getExpectedToolOutput(changes);
 
 		String[] options = { "--tool", "-t", };
 
 		for (String option : options) {
 			assertArrayOfLinesEquals("Incorrect output for option: " + option,
-					expectedOutput, runAndCaptureUsingInitRaw("difftool",
+					expectedOutput, runAndCaptureUsingInitRaw(DIFF_TOOL,
 							"--trust-exit-code", option, TOOL_NAME));
 		}
 	}
@@ -125,13 +87,13 @@ public class DiffToolTest extends CLIRepositoryTestCase {
 	public void testToolNoGuiNoPromptNoTrustExitcode() throws Exception {
 		RevCommit commit = createUnstagedChanges();
 		List<DiffEntry> changes = getRepositoryChanges(commit);
-		String[] expectedOutput = getExpectedDiffToolOutput(changes);
+		String[] expectedOutput = getExpectedToolOutput(changes);
 
 		String[] options = { "--tool", "-t", };
 
 		for (String option : options) {
 			assertArrayOfLinesEquals("Incorrect output for option: " + option,
-					expectedOutput, runAndCaptureUsingInitRaw("difftool",
+					expectedOutput, runAndCaptureUsingInitRaw(DIFF_TOOL,
 							"--no-gui", "--no-prompt", "--no-trust-exit-code",
 							option, TOOL_NAME));
 		}
@@ -141,13 +103,13 @@ public class DiffToolTest extends CLIRepositoryTestCase {
 	public void testToolCached() throws Exception {
 		RevCommit commit = createStagedChanges();
 		List<DiffEntry> changes = getRepositoryChanges(commit);
-		String[] expectedOutput = getExpectedDiffToolOutput(changes);
+		String[] expectedOutput = getExpectedToolOutput(changes);
 
 		String[] options = { "--cached", "--staged", };
 
 		for (String option : options) {
 			assertArrayOfLinesEquals("Incorrect output for option: " + option,
-					expectedOutput, runAndCaptureUsingInitRaw("difftool",
+					expectedOutput, runAndCaptureUsingInitRaw(DIFF_TOOL,
 							option, "--tool", TOOL_NAME));
 		}
 	}
@@ -174,7 +136,8 @@ public class DiffToolTest extends CLIRepositoryTestCase {
 
 		String option = "--tool-help";
 		assertArrayOfLinesEquals("Incorrect output for option: " + option,
-				expectedOutput.toArray(new String[0]), runAndCaptureUsingInitRaw("difftool", option));
+				expectedOutput.toArray(new String[0]),
+				runAndCaptureUsingInitRaw(DIFF_TOOL, option));
 	}
 
 	private void configureEchoTool(String toolName) {
@@ -196,33 +159,7 @@ public class DiffToolTest extends CLIRepositoryTestCase {
 				String.valueOf(false));
 	}
 
-	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) {
+	private String[] getExpectedToolOutput(List<DiffEntry> changes) {
 		String[] expectedToolOutput = new String[changes.size()];
 		for (int i = 0; i < changes.size(); ++i) {
 			DiffEntry change = changes.get(i);
@@ -232,17 +169,4 @@ public class DiffToolTest extends CLIRepositoryTestCase {
 		}
 		return expectedToolOutput;
 	}
-
-	private static void assertArrayOfLinesEquals(String failMessage,
-			String[] expected, String[] actual) {
-		assertEquals(failMessage, toString(expected), toString(actual));
-	}
-
-	private static String getEchoCommand() {
-		/*
-		 * use 'MERGED' placeholder, as both 'LOCAL' and 'REMOTE' will be
-		 * replaced with full paths to a temporary file during some of the tests
-		 */
-		return "(echo \"$MERGED\")";
-	}
 }
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/ExternalToolTestCase.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/ExternalToolTestCase.java
new file mode 100644
index 0000000000..e10b13efb1
--- /dev/null
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/ExternalToolTestCase.java
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2022, 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.CherryPickResult;
+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.kohsuke.args4j.Argument;
+
+/**
+ * Base test case for the {@code difftool} and {@code mergetool} commands.
+ */
+public abstract class ExternalToolTestCase 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<>();
+	}
+
+	protected static final String TOOL_NAME = "some_tool";
+
+	private static final String TEST_BRANCH_NAME = "test_branch";
+
+	private Git git;
+
+	@Override
+	@Before
+	public void setUp() throws Exception {
+		super.setUp();
+		git = new Git(db);
+		git.commit().setMessage("initial commit").call();
+		git.branchCreate().setName(TEST_BRANCH_NAME).call();
+	}
+
+	protected 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]);
+	}
+
+	protected CherryPickResult createMergeConflict() throws Exception {
+		writeTrashFile("a", "Hello world a");
+		writeTrashFile("b", "Hello world b");
+		git.add().addFilepattern(".").call();
+		git.commit().setMessage("files a & b added").call();
+		writeTrashFile("a", "Hello world a 1");
+		writeTrashFile("b", "Hello world b 1");
+		git.add().addFilepattern(".").call();
+		RevCommit commit1 = git.commit().setMessage("files a & b commit 1")
+				.call();
+		git.branchCreate().setName("branch_1").call();
+		git.checkout().setName(TEST_BRANCH_NAME).call();
+		writeTrashFile("a", "Hello world a 2");
+		writeTrashFile("b", "Hello world b 2");
+		git.add().addFilepattern(".").call();
+		git.commit().setMessage("files a & b commit 2").call();
+		git.branchCreate().setName("branch_2").call();
+		CherryPickResult result = git.cherryPick().include(commit1).call();
+		return result;
+	}
+
+	protected 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;
+	}
+
+	protected RevCommit createStagedChanges() throws Exception {
+		RevCommit commit = createUnstagedChanges();
+		git.add().addFilepattern(".").call();
+		return commit;
+	}
+
+	protected 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;
+	}
+
+	protected static void assertArrayOfLinesEquals(String failMessage,
+			String[] expected, String[] actual) {
+		assertEquals(failMessage, toString(expected), toString(actual));
+	}
+
+	protected static String getEchoCommand() {
+		/*
+		 * use 'MERGED' placeholder, as both 'LOCAL' and 'REMOTE' will be
+		 * replaced with full paths to a temporary file during some of the tests
+		 */
+		return "(echo \"$MERGED\")";
+	}
+}
diff --git a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/MergeToolTest.java b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/MergeToolTest.java
new file mode 100644
index 0000000000..32cd60415e
--- /dev/null
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/MergeToolTest.java
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2022, 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.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_CMD;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_PROMPT;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_TOOL;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_MERGETOOL_SECTION;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_MERGE_SECTION;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.eclipse.jgit.internal.diffmergetool.CommandLineMergeTool;
+import org.eclipse.jgit.lib.StoredConfig;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Testing the {@code mergetool} command.
+ */
+public class MergeToolTest extends ExternalToolTestCase {
+
+	private static final String MERGE_TOOL = CONFIG_MERGETOOL_SECTION;
+
+	@Override
+	@Before
+	public void setUp() throws Exception {
+		super.setUp();
+		configureEchoTool(TOOL_NAME);
+	}
+
+	@Test
+	public void testTool() throws Exception {
+		createMergeConflict();
+		String[] expectedOutput = getExpectedToolOutput();
+
+		String[] options = {
+				"--tool",
+				"-t",
+		};
+
+		for (String option : options) {
+			assertArrayOfLinesEquals("Incorrect output for option: " + option,
+					expectedOutput,
+					runAndCaptureUsingInitRaw(MERGE_TOOL, option,
+							TOOL_NAME));
+		}
+	}
+
+	@Test
+	public void testToolNoGuiNoPrompt() throws Exception {
+		createMergeConflict();
+		String[] expectedOutput = getExpectedToolOutput();
+
+		String[] options = { "--tool", "-t", };
+
+		for (String option : options) {
+			assertArrayOfLinesEquals("Incorrect output for option: " + option,
+					expectedOutput, runAndCaptureUsingInitRaw(MERGE_TOOL,
+							"--no-gui", "--no-prompt", option, TOOL_NAME));
+		}
+	}
+
+	@Test
+	public void testToolHelp() throws Exception {
+		CommandLineMergeTool[] defaultTools = CommandLineMergeTool.values();
+		List<String> expectedOutput = new ArrayList<>();
+		expectedOutput.add(
+				"'git mergetool --tool=<tool>' may be set to one of the following:");
+		for (CommandLineMergeTool defaultTool : defaultTools) {
+			String toolName = defaultTool.name();
+			expectedOutput.add(toolName);
+		}
+		String customToolHelpLine = TOOL_NAME + "." + CONFIG_KEY_CMD + " "
+				+ getEchoCommand();
+		expectedOutput.add("user-defined:");
+		expectedOutput.add(customToolHelpLine);
+		String[] userDefinedToolsHelp = {
+				"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.",
+		};
+		expectedOutput.addAll(Arrays.asList(userDefinedToolsHelp));
+
+		String option = "--tool-help";
+		assertArrayOfLinesEquals("Incorrect output for option: " + option,
+				expectedOutput.toArray(new String[0]),
+				runAndCaptureUsingInitRaw(MERGE_TOOL, option));
+	}
+
+	private void configureEchoTool(String toolName) {
+		StoredConfig config = db.getConfig();
+		// the default merge tool is configured without a subsection
+		String subsection = null;
+		config.setString(CONFIG_MERGE_SECTION, subsection, CONFIG_KEY_TOOL,
+				toolName);
+
+		String command = getEchoCommand();
+
+		config.setString(CONFIG_MERGETOOL_SECTION, toolName, CONFIG_KEY_CMD,
+				command);
+		/*
+		 * prevent prompts as we are running in tests and there is no user to
+		 * interact with on the command line
+		 */
+		config.setString(CONFIG_MERGETOOL_SECTION, toolName, CONFIG_KEY_PROMPT,
+				String.valueOf(false));
+	}
+
+	private String[] getExpectedToolOutput() {
+		String[] mergeConflictFilenames = { "a", "b", };
+		List<String> expectedOutput = new ArrayList<>();
+		expectedOutput.add("Merging:");
+		for (String mergeConflictFilename : mergeConflictFilenames) {
+			expectedOutput.add(mergeConflictFilename);
+		}
+		for (String mergeConflictFilename : mergeConflictFilenames) {
+			expectedOutput.add("Normal merge conflict for '"
+					+ mergeConflictFilename + "':");
+			expectedOutput.add("{local}: modified file");
+			expectedOutput.add("{remote}: modified file");
+			expectedOutput.add("TODO: Launch mergetool '" + TOOL_NAME
+					+ "' for path '" + mergeConflictFilename + "'...");
+		}
+		return expectedOutput.toArray(new String[0]);
+	}
+}