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>

2 files changed, 214 insertions, 2 deletions

diff --git a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/DiffTool.java b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/DiffTool.java
index 2f74177452..2e90d52cba 100644
--- a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/DiffTool.java
+++ b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/DiffTool.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2018-2021, Andre Bossert <andre.bossert@siemens.com>
+ * Copyright (C) 2018-2022, Andre Bossert <andre.bossert@siemens.com>
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Distribution License v. 1.0 which is available at
@@ -192,7 +192,7 @@ class DiffTool extends TextBuiltin {
 						outw.flush();
 						errw.println(e.getMessage());
 						throw die(MessageFormat.format(
-								CLIText.get().diffToolDied, mergedFilePath, e));
+								CLIText.get().diffToolDied, mergedFilePath), e);
 					}
 				} else {
 					break;
diff --git a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/MergeTool.java b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/MergeTool.java
new file mode 100644
index 0000000000..37afa54c78
--- /dev/null
+++ b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/MergeTool.java
@@ -0,0 +1,212 @@
+/*
+ * Copyright (C) 2018-2022, Andre Bossert <andre.bossert@siemens.com>
+ *
+ * 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 java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.TreeMap;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.Status;
+import org.eclipse.jgit.api.StatusCommand;
+import org.eclipse.jgit.api.errors.GitAPIException;
+import org.eclipse.jgit.internal.diffmergetool.ExternalMergeTool;
+import org.eclipse.jgit.errors.NoWorkTreeException;
+import org.eclipse.jgit.errors.RevisionSyntaxException;
+import org.eclipse.jgit.internal.diffmergetool.MergeTools;
+import org.eclipse.jgit.lib.IndexDiff.StageState;
+import org.eclipse.jgit.lib.internal.BooleanTriState;
+import org.eclipse.jgit.lib.Repository;
+import org.kohsuke.args4j.Argument;
+import org.kohsuke.args4j.Option;
+import org.kohsuke.args4j.spi.RestOfArgumentsHandler;
+
+@Command(name = "mergetool", common = true, usage = "usage_MergeTool")
+class MergeTool extends TextBuiltin {
+	private MergeTools mergeTools;
+
+	@Option(name = "--tool", aliases = {
+			"-t" }, metaVar = "metaVar_tool", usage = "usage_ToolForMerge")
+	private String toolName;
+
+	private Optional<Boolean> prompt = Optional.empty();
+
+	@Option(name = "--prompt", usage = "usage_prompt")
+	void setPrompt(@SuppressWarnings("unused") boolean on) {
+		prompt = Optional.of(Boolean.TRUE);
+	}
+
+	@Option(name = "--no-prompt", aliases = { "-y" }, usage = "usage_noPrompt")
+	void noPrompt(@SuppressWarnings("unused") boolean on) {
+		prompt = Optional.of(Boolean.FALSE);
+	}
+
+	@Option(name = "--tool-help", usage = "usage_toolHelp")
+	private boolean toolHelp;
+
+	private BooleanTriState gui = BooleanTriState.UNSET;
+
+	@Option(name = "--gui", aliases = { "-g" }, usage = "usage_MergeGuiTool")
+	void setGui(@SuppressWarnings("unused") boolean on) {
+		gui = BooleanTriState.TRUE;
+	}
+
+	@Option(name = "--no-gui", usage = "usage_noGui")
+	void noGui(@SuppressWarnings("unused") boolean on) {
+		gui = BooleanTriState.FALSE;
+	}
+
+	@Argument(required = false, index = 0, metaVar = "metaVar_paths")
+	@Option(name = "--", metaVar = "metaVar_paths", handler = RestOfArgumentsHandler.class)
+	protected List<String> filterPaths;
+
+	@Override
+	protected void init(Repository repository, String gitDir) {
+		super.init(repository, gitDir);
+		mergeTools = new MergeTools(repository);
+	}
+
+	@Override
+	protected void run() {
+		try {
+			if (toolHelp) {
+				showToolHelp();
+			} else {
+				// get prompt
+				boolean showPrompt = mergeTools.isInteractive();
+				if (prompt.isPresent()) {
+					showPrompt = prompt.get().booleanValue();
+				}
+				// get passed or default tool name
+				String toolNameSelected = toolName;
+				if ((toolNameSelected == null) || toolNameSelected.isEmpty()) {
+					toolNameSelected = mergeTools.getDefaultToolName(gui);
+				}
+				// get the changed files
+				Map<String, StageState> files = getFiles();
+				if (files.size() > 0) {
+					merge(files, showPrompt, toolNameSelected);
+				} else {
+					outw.println("No files need merging"); //$NON-NLS-1$
+				}
+			}
+			outw.flush();
+		} catch (Exception e) {
+			throw die(e.getMessage(), e);
+		}
+	}
+
+	private void merge(Map<String, StageState> files, boolean showPrompt,
+			String toolNamePrompt) throws Exception {
+		// sort file names
+		List<String> fileNames = new ArrayList<>(files.keySet());
+		Collections.sort(fileNames);
+		// show the files
+		outw.println("Merging:"); //$NON-NLS-1$
+		for (String fileName : fileNames) {
+			outw.println(fileName);
+		}
+		outw.flush();
+		for (String fileName : fileNames) {
+			StageState fileState = files.get(fileName);
+			// only both-modified is valid for mergetool
+			if (fileState == StageState.BOTH_MODIFIED) {
+				outw.println("\nNormal merge conflict for '" + fileName + "':"); //$NON-NLS-1$ //$NON-NLS-2$
+				outw.println("  {local}: modified file"); //$NON-NLS-1$
+				outw.println("  {remote}: modified file"); //$NON-NLS-1$
+				// check if user wants to launch merge resolution tool
+				boolean launch = true;
+				if (showPrompt) {
+					launch = isLaunch(toolNamePrompt);
+				}
+				if (launch) {
+					outw.println("TODO: Launch mergetool '" + toolNamePrompt //$NON-NLS-1$
+							+ "' for path '" + fileName + "'..."); //$NON-NLS-1$ //$NON-NLS-2$
+				} else {
+					break;
+				}
+			} else if ((fileState == StageState.DELETED_BY_US) || (fileState == StageState.DELETED_BY_THEM)) {
+				outw.println("\nDeleted merge conflict for '" + fileName + "':"); //$NON-NLS-1$ //$NON-NLS-2$
+			} else {
+				outw.println(
+						"\nUnknown merge conflict for '" + fileName + "':"); //$NON-NLS-1$ //$NON-NLS-2$
+				break;
+			}
+		}
+	}
+
+	private boolean isLaunch(String toolNamePrompt)
+			throws IOException {
+		boolean launch = true;
+		outw.println("Hit return to start merge resolution tool (" //$NON-NLS-1$
+				+ toolNamePrompt + "): "); //$NON-NLS-1$
+		outw.flush();
+		BufferedReader br = new BufferedReader(new InputStreamReader(ins));
+		String line = null;
+		if ((line = br.readLine()) != null) {
+			if (!line.equalsIgnoreCase("Y") && !line.equalsIgnoreCase("")) { //$NON-NLS-1$ //$NON-NLS-2$
+				launch = false;
+			}
+		}
+		return launch;
+	}
+
+	private void showToolHelp() throws IOException {
+		outw.println(
+				"'git mergetool --tool=<tool>' may be set to one of the following:"); //$NON-NLS-1$
+		for (String name : mergeTools.getAvailableTools().keySet()) {
+			outw.println("\t\t" + name); //$NON-NLS-1$
+		}
+		outw.println(""); //$NON-NLS-1$
+		outw.println("\tuser-defined:"); //$NON-NLS-1$
+		Map<String, ExternalMergeTool> userTools = mergeTools
+				.getUserDefinedTools();
+		for (String name : userTools.keySet()) {
+			outw.println("\t\t" + name + ".cmd " //$NON-NLS-1$ //$NON-NLS-2$
+					+ userTools.get(name).getCommand());
+		}
+		outw.println(""); //$NON-NLS-1$
+		outw.println(
+				"The following tools are valid, but not currently available:"); //$NON-NLS-1$
+		for (String name : mergeTools.getNotAvailableTools().keySet()) {
+			outw.println("\t\t" + name); //$NON-NLS-1$
+		}
+		outw.println(""); //$NON-NLS-1$
+		outw.println("Some of the tools listed above only work in a windowed"); //$NON-NLS-1$
+		outw.println(
+				"environment. If run in a terminal-only session, they will fail."); //$NON-NLS-1$
+		return;
+	}
+
+	private Map<String, StageState> getFiles()
+			throws RevisionSyntaxException, NoWorkTreeException,
+			GitAPIException {
+		Map<String, StageState> files = new TreeMap<>();
+		try (Git git = new Git(db)) {
+			StatusCommand statusCommand = git.status();
+			if (filterPaths != null && filterPaths.size() > 0) {
+				for (String path : filterPaths) {
+					statusCommand.addPath(path);
+				}
+			}
+			Status status = statusCommand.call();
+			files = status.getConflictingStageState();
+		}
+		return files;
+	}
+
+}