Merge "Add command line support for "git mergetool""

8 files changed, 573 insertions, 52 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/CommandLineMergeTool.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/CommandLineMergeTool.java
new file mode 100644
index 0000000000..3a22124328
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/CommandLineMergeTool.java
@@ -0,0 +1,327 @@
+/*
+ * 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.internal.diffmergetool;
+
+/**
+ * Pre-defined merge tools.
+ *
+ * Adds same merge tools as also pre-defined in C-Git see "git-core\mergetools\"
+ * see links to command line parameter description for the tools
+ *
+ * <pre>
+ * araxis
+ * bc
+ * bc3
+ * codecompare
+ * deltawalker
+ * diffmerge
+ * diffuse
+ * ecmerge
+ * emerge
+ * examdiff
+ * guiffy
+ * gvimdiff
+ * gvimdiff2
+ * gvimdiff3
+ * kdiff3
+ * kompare
+ * meld
+ * opendiff
+ * p4merge
+ * tkdiff
+ * tortoisemerge
+ * vimdiff
+ * vimdiff2
+ * vimdiff3
+ * winmerge
+ * xxdiff
+ * </pre>
+ *
+ */
+@SuppressWarnings("nls")
+public enum CommandLineMergeTool {
+	/**
+	 * See: <a href=
+	 * "https://www.araxis.com/merge/documentation-windows/command-line.en">https://www.araxis.com/merge/documentation-windows/command-line.en</a>
+	 */
+	araxis("compare",
+			"-wait -merge -3 -a1 \"$BASE\" \"$LOCAL\" \"$REMOTE\" \"$MERGED\"",
+			"-wait -2 \"$LOCAL\" \"$REMOTE\" \"$MERGED\"",
+			false),
+	/**
+	 * See: <a href=
+	 * "https://www.scootersoftware.com/v4help/index.html?command_line_reference.html">https://www.scootersoftware.com/v4help/index.html?command_line_reference.html</a>
+	 */
+	bc("bcomp", "\"$LOCAL\" \"$REMOTE\" \"$BASE\" --mergeoutput=\"$MERGED\"",
+			"\"$LOCAL\" \"$REMOTE\" --mergeoutput=\"$MERGED\"",
+			false),
+	/**
+	 * See: <a href=
+	 * "https://www.scootersoftware.com/v4help/index.html?command_line_reference.html">https://www.scootersoftware.com/v4help/index.html?command_line_reference.html</a>
+	 */
+	bc3("bcompare", bc),
+	/**
+	 * See: <a href=
+	 * "https://www.devart.com/codecompare/docs/index.html?merging_via_command_line.htm">https://www.devart.com/codecompare/docs/index.html?merging_via_command_line.htm</a>
+	 */
+	codecompare("CodeMerge",
+			"-MF=\"$LOCAL\" -TF=\"$REMOTE\" -BF=\"$BASE\" -RF=\"$MERGED\"",
+			"-MF=\"$LOCAL\" -TF=\"$REMOTE\" -RF=\"$MERGED\"",
+			false),
+	/**
+	 * See: <a href=
+	 * "https://www.deltawalker.com/integrate/command-line">https://www.deltawalker.com/integrate/command-line</a>
+	 * <p>
+	 * Hint: $(pwd) command must be defined
+	 * </p>
+	 */
+	deltawalker("DeltaWalker",
+			"\"$LOCAL\" \"$REMOTE\" \"$BASE\" -pwd=\"$(pwd)\" -merged=\"$MERGED\"",
+			"\"$LOCAL\" \"$REMOTE\" -pwd=\"$(pwd)\" -merged=\"$MERGED\"",
+			true),
+	/**
+	 * See: <a href=
+	 * "https://sourcegear.com/diffmerge/webhelp/sec__clargs__diff.html">https://sourcegear.com/diffmerge/webhelp/sec__clargs__diff.html</a>
+	 */
+	diffmerge("diffmerge", //$NON-NLS-1$
+			"--merge --result=\"$MERGED\" \"$LOCAL\" \"$BASE\" \"$REMOTE\"",
+			"--merge --result=\"$MERGED\" \"$LOCAL\" \"$REMOTE\"",
+			true),
+	/**
+	 * See: <a href=
+	 * "http://diffuse.sourceforge.net/manual.html#introduction-usage">http://diffuse.sourceforge.net/manual.html#introduction-usage</a>
+	 * <p>
+	 * Hint: check the ' | cat' for the call
+	 * </p>
+	 */
+	diffuse("diffuse", "\"$LOCAL\" \"$MERGED\" \"$REMOTE\" \"$BASE\"",
+			"\"$LOCAL\" \"$MERGED\" \"$REMOTE\"", false),
+	/**
+	 * See: <a href=
+	 * "http://www.elliecomputing.com/en/OnlineDoc/ecmerge_en/44205167.asp">http://www.elliecomputing.com/en/OnlineDoc/ecmerge_en/44205167.asp</a>
+	 */
+	ecmerge("ecmerge",
+			"--default --mode=merge3 \"$BASE\" \"$LOCAL\" \"$REMOTE\" --to=\"$MERGED\"",
+			"--default --mode=merge2 \"$LOCAL\" \"$REMOTE\" --to=\"$MERGED\"",
+			false),
+	/**
+	 * See: <a href=
+	 * "https://www.gnu.org/software/emacs/manual/html_node/emacs/Overview-of-Emerge.html">https://www.gnu.org/software/emacs/manual/html_node/emacs/Overview-of-Emerge.html</a>
+	 * <p>
+	 * Hint: $(basename) command must be defined
+	 * </p>
+	 */
+	emerge("emacs",
+			"-f emerge-files-with-ancestor-command \"$LOCAL\" \"$REMOTE\" \"$BASE\" \"$(basename \"$MERGED\")\"",
+			"-f emerge-files-command \"$LOCAL\" \"$REMOTE\" \"$(basename \"$MERGED\")\"",
+			true),
+	/**
+	 * See: <a href=
+	 * "https://www.prestosoft.com/ps.asp?page=htmlhelp/edp/command_line_options">https://www.prestosoft.com/ps.asp?page=htmlhelp/edp/command_line_options</a>
+	 */
+	examdiff("ExamDiff",
+			"-merge \"$LOCAL\" \"$BASE\" \"$REMOTE\" -o:\"$MERGED\" -nh",
+			"-merge \"$LOCAL\" \"$REMOTE\" -o:\"$MERGED\" -nh",
+			false),
+	/**
+	 * See: <a href=
+	 * "https://www.guiffy.com/help/GuiffyHelp/GuiffyCmd.html">https://www.guiffy.com/help/GuiffyHelp/GuiffyCmd.html</a>
+	 */
+	guiffy("guiffy", "-s \"$LOCAL\" \"$REMOTE\" \"$BASE\" \"$MERGED\"",
+			"-m \"$LOCAL\" \"$REMOTE\" \"$MERGED\"", true),
+	/**
+	 * See: <a href=
+	 * "http://vimdoc.sourceforge.net/htmldoc/diff.html">http://vimdoc.sourceforge.net/htmldoc/diff.html</a>
+	 */
+	gvimdiff("gvim",
+			"-f -d -c '4wincmd w | wincmd J' \"$LOCAL\" \"$BASE\" \"$REMOTE\" \"$MERGED\"",
+			"-f -d -c 'wincmd l' \"$LOCAL\" \"$MERGED\" \"$REMOTE\"",
+			true),
+	/**
+	 * See: <a href=
+	 * "http://vimdoc.sourceforge.net/htmldoc/diff.html">http://vimdoc.sourceforge.net/htmldoc/diff.html</a>
+	 */
+	gvimdiff2("gvim", "-f -d -c 'wincmd l' \"$LOCAL\" \"$MERGED\" \"$REMOTE\"",
+			"-f -d -c 'wincmd l' \"$LOCAL\" \"$MERGED\" \"$REMOTE\"", true),
+	/**
+	 * See: <a href= "http://vimdoc.sourceforge.net/htmldoc/diff.html"></a>
+	 */
+	gvimdiff3("gvim",
+			"-f -d -c 'hid | hid | hid' \"$LOCAL\" \"$REMOTE\" \"$BASE\" \"$MERGED\"",
+			"-f -d -c 'hid | hid' \"$LOCAL\" \"$REMOTE\" \"$MERGED\"", true),
+	/**
+	 * See: <a href=
+	 * "http://kdiff3.sourceforge.net/doc/documentation.html">http://kdiff3.sourceforge.net/doc/documentation.html</a>
+	 */
+	kdiff3("kdiff3",
+			"--auto --L1 \"$MERGED (Base)\" --L2 \"$MERGED (Local)\" --L3 \"$MERGED (Remote)\" -o \"$MERGED\" \"$BASE\" \"$LOCAL\" \"$REMOTE\"",
+			"--auto --L1 \"$MERGED (Local)\" --L2 \"$MERGED (Remote)\" -o \"$MERGED\" \"$LOCAL\" \"$REMOTE\"",
+			true),
+	/**
+	 * See: <a href=
+	 * "http://meldmerge.org/help/file-mode.html">http://meldmerge.org/help/file-mode.html</a>
+	 * <p>
+	 * Hint: use meld with output option only (new versions)
+	 * </p>
+	 */
+	meld("meld", "--output=\"$MERGED\" \"$LOCAL\" \"$BASE\" \"$REMOTE\"",
+			"\"$LOCAL\" \"$MERGED\" \"$REMOTE\"",
+			false),
+	/**
+	 * See: <a href=
+	 * "http://www.manpagez.com/man/1/opendiff/">http://www.manpagez.com/man/1/opendiff/</a>
+	 * <p>
+	 * Hint: check the ' | cat' for the call
+	 * </p>
+	 */
+	opendiff("opendiff",
+			"\"$LOCAL\" \"$REMOTE\" -ancestor \"$BASE\" -merge \"$MERGED\"",
+			"\"$LOCAL\" \"$REMOTE\" -merge \"$MERGED\"",
+			false),
+	/**
+	 * See: <a href=
+	 * "https://www.perforce.com/manuals/v15.1/cmdref/p4_merge.html">https://www.perforce.com/manuals/v15.1/cmdref/p4_merge.html</a>
+	 * <p>
+	 * Hint: check how to fix "no base present" / create_virtual_base problem
+	 * </p>
+	 */
+	p4merge("p4merge", "\"$BASE\" \"$REMOTE\" \"$LOCAL\" \"$MERGED\"",
+			"\"$REMOTE\" \"$LOCAL\" \"$MERGED\"", false),
+	/**
+	 * See: <a href=
+	 * "http://linux.math.tifr.res.in/manuals/man/tkdiff.html">http://linux.math.tifr.res.in/manuals/man/tkdiff.html</a>
+	 */
+	tkdiff("tkdiff", "-a \"$BASE\" -o \"$MERGED\" \"$LOCAL\" \"$REMOTE\"",
+			"-o \"$MERGED\" \"$LOCAL\" \"$REMOTE\"",
+			true),
+	/**
+	 * See: <a href=
+	 * "https://tortoisegit.org/docs/tortoisegitmerge/tme-automation.html#tme-automation-basics">https://tortoisegit.org/docs/tortoisegitmerge/tme-automation.html#tme-automation-basics</a>
+	 * <p>
+	 * Hint: merge without base is not supported
+	 * </p>
+	 * <p>
+	 * Hint: cannot diff
+	 * </p>
+	 */
+	tortoisegitmerge("tortoisegitmerge",
+			"-base \"$BASE\" -mine \"$LOCAL\" -theirs \"$REMOTE\" -merged \"$MERGED\"",
+			null, false),
+	/**
+	 * See: <a href=
+	 * "https://tortoisegit.org/docs/tortoisegitmerge/tme-automation.html#tme-automation-basics">https://tortoisegit.org/docs/tortoisegitmerge/tme-automation.html#tme-automation-basics</a>
+	 * <p>
+	 * Hint: merge without base is not supported
+	 * </p>
+	 * <p>
+	 * Hint: cannot diff
+	 * </p>
+	 */
+	tortoisemerge("tortoisemerge",
+			"-base:\"$BASE\" -mine:\"$LOCAL\" -theirs:\"$REMOTE\" -merged:\"$MERGED\"",
+			null, false),
+	/**
+	 * See: <a href=
+	 * "http://vimdoc.sourceforge.net/htmldoc/diff.html">http://vimdoc.sourceforge.net/htmldoc/diff.html</a>
+	 */
+	vimdiff("vim", gvimdiff),
+	/**
+	 * See: <a href=
+	 * "http://vimdoc.sourceforge.net/htmldoc/diff.html">http://vimdoc.sourceforge.net/htmldoc/diff.html</a>
+	 */
+	vimdiff2("vim", gvimdiff2),
+	/**
+	 * See: <a href=
+	 * "http://vimdoc.sourceforge.net/htmldoc/diff.html">http://vimdoc.sourceforge.net/htmldoc/diff.html</a>
+	 */
+	vimdiff3("vim", gvimdiff3),
+	/**
+	 * See: <a href=
+	 * "http://manual.winmerge.org/Command_line.html">http://manual.winmerge.org/Command_line.html</a>
+	 * <p>
+	 * Hint: check how 'mergetool_find_win32_cmd "WinMergeU.exe" "WinMerge"'
+	 * works
+	 * </p>
+	 */
+	winmerge("WinMergeU",
+			"-u -e -dl Local -dr Remote \"$LOCAL\" \"$REMOTE\" \"$MERGED\"",
+			"-u -e -dl Local -dr Remote \"$LOCAL\" \"$REMOTE\" \"$MERGED\"",
+			false),
+	/**
+	 * See: <a href=
+	 * "http://furius.ca/xxdiff/doc/xxdiff-doc.html">http://furius.ca/xxdiff/doc/xxdiff-doc.html</a>
+	 */
+	xxdiff("xxdiff",
+			"-X --show-merged-pane -R 'Accel.SaveAsMerged: \"Ctrl+S\"' -R 'Accel.Search: \"Ctrl+F\"' -R 'Accel.SearchForward: \"Ctrl+G\"' --merged-file \"$MERGED\" \"$LOCAL\" \"$BASE\" \"$REMOTE\"",
+			"-X -R 'Accel.SaveAsMerged: \"Ctrl+S\"' -R 'Accel.Search: \"Ctrl+F\"' -R 'Accel.SearchForward: \"Ctrl+G\"' --merged-file \"$MERGED\" \"$LOCAL\" \"$REMOTE\"",
+			false);
+
+	CommandLineMergeTool(String path, String parametersWithBase,
+			String parametersWithoutBase,
+			boolean exitCodeTrustable) {
+		this.path = path;
+		this.parametersWithBase = parametersWithBase;
+		this.parametersWithoutBase = parametersWithoutBase;
+		this.exitCodeTrustable = exitCodeTrustable;
+    }
+
+	CommandLineMergeTool(CommandLineMergeTool from) {
+		this(from.getPath(), from.getParameters(true),
+				from.getParameters(false), from.isExitCodeTrustable());
+	}
+
+	CommandLineMergeTool(String path, CommandLineMergeTool from) {
+		this(path, from.getParameters(true), from.getParameters(false),
+				from.isExitCodeTrustable());
+	}
+
+	private final String path;
+
+	private final String parametersWithBase;
+
+	private final String parametersWithoutBase;
+
+	private final boolean exitCodeTrustable;
+
+	/**
+	 * @return path
+	 */
+	public String getPath() {
+		return path;
+	}
+
+	/**
+	 * @param withBase
+	 *            return parameters with base present?
+	 * @return parameters with or without base present
+	 */
+	public String getParameters(boolean withBase) {
+		if (withBase) {
+			return parametersWithBase;
+		}
+		return parametersWithoutBase;
+	}
+
+	/**
+	 * @return parameters
+	 */
+	public boolean isExitCodeTrustable() {
+		return exitCodeTrustable;
+	}
+
+	/**
+	 * @return true if command with base present is valid, false otherwise
+	 */
+	public boolean canMergeWithoutBasePresent() {
+		return parametersWithoutBase != null;
+	}
+
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/DiffTools.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/DiffTools.java
index b15cbdc34a..2f2b9de818 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/DiffTools.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/DiffTools.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
@@ -56,8 +56,7 @@ public class DiffTools {
 	 * @param remoteFile
 	 *            the remote file element
 	 * @param mergedFilePath
-	 *            the path of 'merged' file, it equals local or remote path for
-	 *            difftool
+	 *            the path of 'merged' file, it equals local or remote path
 	 * @param toolName
 	 *            the selected tool name (can be null)
 	 * @param prompt
@@ -66,7 +65,7 @@ public class DiffTools {
 	 *            the GUI option
 	 * @param trustExitCode
 	 *            the "trust exit code" option
-	 * @return the return code from executed tool
+	 * @return the execution result from tool
 	 * @throws ToolException
 	 */
 	public ExecutionResult compare(Repository repo, FileElement localFile,
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/ExternalMergeTool.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/ExternalMergeTool.java
index bcc749adad..0c3ddf9afe 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/ExternalMergeTool.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/ExternalMergeTool.java
@@ -10,6 +10,8 @@
 
 package org.eclipse.jgit.internal.diffmergetool;
 
+import org.eclipse.jgit.lib.internal.BooleanTriState;
+
 /**
  * The merge tool interface.
  */
@@ -18,6 +20,14 @@ public interface ExternalMergeTool extends ExternalDiffTool {
 	/**
 	 * @return the tool "trust exit code" option
 	 */
-	boolean isTrustExitCode();
+	BooleanTriState getTrustExitCode();
+
+	/**
+	 * @param withBase
+	 *            get command with base present (true) or without base present
+	 *            (false)
+	 * @return the tool command
+	 */
+	String getCommand(boolean withBase);
 
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/MergeToolConfig.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/MergeToolConfig.java
index e912822613..9be20b75ad 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/MergeToolConfig.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/MergeToolConfig.java
@@ -10,13 +10,24 @@
 
 package org.eclipse.jgit.internal.diffmergetool;
 
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_CMD;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_GUITOOL;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_KEEP_BACKUP;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_KEEP_TEMPORARIES;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_PATH;
+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_KEY_TRUST_EXIT_CODE;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_WRITE_TO_TEMP;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_MERGETOOL_SECTION;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_MERGE_SECTION;
+
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
 
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.Config.SectionParser;
-import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.internal.BooleanTriState;
 
 /**
@@ -42,31 +53,27 @@ public class MergeToolConfig {
 	private final Map<String, ExternalMergeTool> tools;
 
 	private MergeToolConfig(Config rc) {
-		toolName = rc.getString(ConfigConstants.CONFIG_MERGE_SECTION, null,
-				ConfigConstants.CONFIG_KEY_TOOL);
-		guiToolName = rc.getString(ConfigConstants.CONFIG_MERGE_SECTION, null,
-				ConfigConstants.CONFIG_KEY_GUITOOL);
-		prompt = rc.getBoolean(ConfigConstants.CONFIG_MERGETOOL_SECTION,
-				ConfigConstants.CONFIG_KEY_PROMPT, true);
-		keepBackup = rc.getBoolean(ConfigConstants.CONFIG_MERGETOOL_SECTION,
-				ConfigConstants.CONFIG_KEY_KEEP_BACKUP, true);
-		keepTemporaries = rc.getBoolean(
-				ConfigConstants.CONFIG_MERGETOOL_SECTION,
-				ConfigConstants.CONFIG_KEY_KEEP_TEMPORARIES, false);
-		writeToTemp = rc.getBoolean(ConfigConstants.CONFIG_MERGETOOL_SECTION,
-				ConfigConstants.CONFIG_KEY_WRITE_TO_TEMP, false);
+		toolName = rc.getString(CONFIG_MERGE_SECTION, null, CONFIG_KEY_TOOL);
+		guiToolName = rc.getString(CONFIG_MERGE_SECTION, null,
+				CONFIG_KEY_GUITOOL);
+		prompt = rc.getBoolean(CONFIG_MERGETOOL_SECTION, toolName,
+				CONFIG_KEY_PROMPT, true);
+		keepBackup = rc.getBoolean(CONFIG_MERGETOOL_SECTION,
+				CONFIG_KEY_KEEP_BACKUP, true);
+		keepTemporaries = rc.getBoolean(CONFIG_MERGETOOL_SECTION,
+				CONFIG_KEY_KEEP_TEMPORARIES, false);
+		writeToTemp = rc.getBoolean(CONFIG_MERGETOOL_SECTION,
+				CONFIG_KEY_WRITE_TO_TEMP, false);
 		tools = new HashMap<>();
-		Set<String> subsections = rc
-				.getSubsections(ConfigConstants.CONFIG_MERGETOOL_SECTION);
+		Set<String> subsections = rc.getSubsections(CONFIG_MERGETOOL_SECTION);
 		for (String name : subsections) {
-			String cmd = rc.getString(ConfigConstants.CONFIG_MERGETOOL_SECTION,
-					name, ConfigConstants.CONFIG_KEY_CMD);
-			String path = rc.getString(ConfigConstants.CONFIG_MERGETOOL_SECTION,
-					name, ConfigConstants.CONFIG_KEY_PATH);
+			String cmd = rc.getString(CONFIG_MERGETOOL_SECTION, name,
+					CONFIG_KEY_CMD);
+			String path = rc.getString(CONFIG_MERGETOOL_SECTION, name,
+					CONFIG_KEY_PATH);
 			BooleanTriState trustExitCode = BooleanTriState.FALSE;
-			String trustStr = rc.getString(
-					ConfigConstants.CONFIG_MERGETOOL_SECTION, name,
-					ConfigConstants.CONFIG_KEY_TRUST_EXIT_CODE);
+			String trustStr = rc.getString(CONFIG_MERGETOOL_SECTION, name,
+					CONFIG_KEY_TRUST_EXIT_CODE);
 			if (trustStr != null) {
 				trustExitCode = Boolean.valueOf(trustStr).booleanValue()
 						? BooleanTriState.TRUE
@@ -75,9 +82,8 @@ public class MergeToolConfig {
 				trustExitCode = BooleanTriState.UNSET;
 			}
 			if ((cmd != null) || (path != null)) {
-				tools.put(name,
-						new UserDefinedMergeTool(name, path, cmd,
-								trustExitCode));
+				tools.put(name, new UserDefinedMergeTool(name, path, cmd,
+						trustExitCode));
 			}
 		}
 	}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/MergeTools.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/MergeTools.java
index bb5d73eeb2..cefefb8e75 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/MergeTools.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/MergeTools.java
@@ -9,17 +9,21 @@
  */
 package org.eclipse.jgit.internal.diffmergetool;
 
+import java.io.File;
 import java.util.Map;
 import java.util.Set;
 import java.util.TreeMap;
 
+import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.lib.internal.BooleanTriState;
+import org.eclipse.jgit.util.FS.ExecutionResult;
 
 /**
  * Manages merge tools.
  */
 public class MergeTools {
+
 	private final MergeToolConfig config;
 
 	private final Map<String, ExternalMergeTool> predefinedTools;
@@ -33,10 +37,12 @@ public class MergeTools {
 	public MergeTools(Repository repo) {
 		config = repo.getConfig().get(MergeToolConfig.KEY);
 		predefinedTools = setupPredefinedTools();
-		userDefinedTools = setupUserDefinedTools();
+		userDefinedTools = setupUserDefinedTools(config, predefinedTools);
 	}
 
 	/**
+	 * @param repo
+	 *            the repository
 	 * @param localFile
 	 *            the local file element
 	 * @param remoteFile
@@ -49,19 +55,43 @@ public class MergeTools {
 	 *            the selected tool name (can be null)
 	 * @param prompt
 	 *            the prompt option
-	 * @param trustExitCode
-	 *            the "trust exit code" option
 	 * @param gui
 	 *            the GUI option
 	 * @return the execution result from tool
 	 * @throws ToolException
 	 */
-	public int merge(String localFile,
-			String remoteFile, String baseFile, String mergedFilePath,
-			String toolName, BooleanTriState prompt, BooleanTriState gui,
-			BooleanTriState trustExitCode)
+	public ExecutionResult merge(Repository repo, FileElement localFile,
+			FileElement remoteFile, FileElement baseFile, String mergedFilePath,
+			String toolName, BooleanTriState prompt, BooleanTriState gui)
 			throws ToolException {
-		return 0;
+		ExternalMergeTool tool = guessTool(toolName, gui);
+		try {
+			File workingDir = repo.getWorkTree();
+			String localFilePath = localFile.getFile().getPath();
+			String remoteFilePath = remoteFile.getFile().getPath();
+			String baseFilePath = baseFile.getFile().getPath();
+			String command = tool.getCommand();
+			command = command.replace("$LOCAL", localFilePath); //$NON-NLS-1$
+			command = command.replace("$REMOTE", remoteFilePath); //$NON-NLS-1$
+			command = command.replace("$MERGED", mergedFilePath); //$NON-NLS-1$
+			command = command.replace("$BASE", baseFilePath); //$NON-NLS-1$
+			Map<String, String> env = new TreeMap<>();
+			env.put(Constants.GIT_DIR_KEY,
+					repo.getDirectory().getAbsolutePath());
+			env.put("LOCAL", localFilePath); //$NON-NLS-1$
+			env.put("REMOTE", remoteFilePath); //$NON-NLS-1$
+			env.put("MERGED", mergedFilePath); //$NON-NLS-1$
+			env.put("BASE", baseFilePath); //$NON-NLS-1$
+			boolean trust = tool.getTrustExitCode() == BooleanTriState.TRUE;
+			CommandExecutor cmdExec = new CommandExecutor(repo.getFS(), trust);
+			return cmdExec.run(command, workingDir, env);
+		} catch (Exception e) {
+			throw new ToolException(e);
+		} finally {
+			localFile.cleanTemporaries();
+			remoteFile.cleanTemporaries();
+			baseFile.cleanTemporaries();
+		}
 	}
 
 	/**
@@ -99,7 +129,7 @@ public class MergeTools {
 	 */
 	public String getDefaultToolName(BooleanTriState gui) {
 		return gui != BooleanTriState.UNSET ? "my_gui_tool" //$NON-NLS-1$
-				: "my_default_toolname"; //$NON-NLS-1$
+				: config.getDefaultToolName();
 	}
 
 	/**
@@ -109,11 +139,58 @@ public class MergeTools {
 		return config.isPrompt();
 	}
 
+	private ExternalMergeTool guessTool(String toolName, BooleanTriState gui)
+			throws ToolException {
+		if ((toolName == null) || toolName.isEmpty()) {
+			toolName = getDefaultToolName(gui);
+		}
+		ExternalMergeTool tool = getTool(toolName);
+		if (tool == null) {
+			throw new ToolException("Unknown diff tool " + toolName); //$NON-NLS-1$
+		}
+		return tool;
+	}
+
+	private ExternalMergeTool getTool(final String name) {
+		ExternalMergeTool tool = userDefinedTools.get(name);
+		if (tool == null) {
+			tool = predefinedTools.get(name);
+		}
+		return tool;
+	}
+
 	private Map<String, ExternalMergeTool> setupPredefinedTools() {
-		return new TreeMap<>();
+		Map<String, ExternalMergeTool> tools = new TreeMap<>();
+		for (CommandLineMergeTool tool : CommandLineMergeTool.values()) {
+			tools.put(tool.name(), new PreDefinedMergeTool(tool));
+		}
+		return tools;
 	}
 
-	private Map<String, ExternalMergeTool> setupUserDefinedTools() {
-		return new TreeMap<>();
+	private Map<String, ExternalMergeTool> setupUserDefinedTools(
+			MergeToolConfig cfg, Map<String, ExternalMergeTool> predefTools) {
+		Map<String, ExternalMergeTool> tools = new TreeMap<>();
+		Map<String, ExternalMergeTool> userTools = cfg.getTools();
+		for (String name : userTools.keySet()) {
+			ExternalMergeTool userTool = userTools.get(name);
+			// if mergetool.<name>.cmd is defined we have user defined tool
+			if (userTool.getCommand() != null) {
+				tools.put(name, userTool);
+			} else if (userTool.getPath() != null) {
+				// if mergetool.<name>.path is defined we just overload the path
+				// of predefined tool
+				PreDefinedMergeTool predefTool = (PreDefinedMergeTool) predefTools
+						.get(name);
+				if (predefTool != null) {
+					predefTool.setPath(userTool.getPath());
+					if (userTool.getTrustExitCode() != BooleanTriState.UNSET) {
+						predefTool
+								.setTrustExitCode(userTool.getTrustExitCode());
+					}
+				}
+			}
+		}
+		return tools;
 	}
-}
\ No newline at end of file
+
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/PreDefinedMergeTool.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/PreDefinedMergeTool.java
new file mode 100644
index 0000000000..2c64c16667
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/PreDefinedMergeTool.java
@@ -0,0 +1,91 @@
+/*
+ * 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.internal.diffmergetool;
+
+import org.eclipse.jgit.lib.internal.BooleanTriState;
+
+/**
+ * The pre-defined merge tool.
+ */
+public class PreDefinedMergeTool extends UserDefinedMergeTool {
+
+	/**
+	 * the tool parameters without base
+	 */
+	private final String parametersWithoutBase;
+
+	/**
+	 * Creates the pre-defined merge tool
+	 *
+	 * @param name
+	 *            the name
+	 * @param path
+	 *            the path
+	 * @param parametersWithBase
+	 *            the tool parameters that are used together with path as
+	 *            command and "base is present" ($BASE)
+	 * @param parametersWithoutBase
+	 *            the tool parameters that are used together with path as
+	 *            command and "base is present" ($BASE)
+	 * @param trustExitCode
+	 *            the "trust exit code" option
+	 */
+	public PreDefinedMergeTool(String name, String path,
+			String parametersWithBase, String parametersWithoutBase,
+			BooleanTriState trustExitCode) {
+		super(name, path, parametersWithBase, trustExitCode);
+		this.parametersWithoutBase = parametersWithoutBase;
+	}
+
+	/**
+	 * Creates the pre-defined merge tool
+	 *
+	 * @param tool
+	 *            the command line merge tool
+	 *
+	 */
+	public PreDefinedMergeTool(CommandLineMergeTool tool) {
+		this(tool.name(), tool.getPath(), tool.getParameters(true),
+				tool.getParameters(false),
+				tool.isExitCodeTrustable() ? BooleanTriState.TRUE
+						: BooleanTriState.FALSE);
+	}
+
+	/**
+	 * @param trustExitCode
+	 *            the "trust exit code" option
+	 */
+	@Override
+	public void setTrustExitCode(BooleanTriState trustExitCode) {
+		super.setTrustExitCode(trustExitCode);
+	}
+
+	/**
+	 * @return the tool command (with base present)
+	 */
+	@Override
+	public String getCommand() {
+		return getCommand(true);
+	}
+
+	/**
+	 * @param withBase
+	 *            get command with base present (true) or without base present
+	 *            (false)
+	 * @return the tool command
+	 */
+	@Override
+	public String getCommand(boolean withBase) {
+		return getPath() + " " //$NON-NLS-1$
+				+ (withBase ? super.getCommand() : parametersWithoutBase);
+	}
+
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/UserDefinedMergeTool.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/UserDefinedMergeTool.java
index df4d8cb8c6..1dd2f0d793 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/UserDefinedMergeTool.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/diffmergetool/UserDefinedMergeTool.java
@@ -21,7 +21,7 @@ public class UserDefinedMergeTool extends UserDefinedDiffTool
 	/**
 	 * the merge tool "trust exit code" option
 	 */
-	private final BooleanTriState trustExitCode;
+	private BooleanTriState trustExitCode;
 
 	/**
 	 * Creates the merge tool
@@ -40,20 +40,30 @@ public class UserDefinedMergeTool extends UserDefinedDiffTool
 		super(name, path, cmd);
 		this.trustExitCode = trustExitCode;
 	}
-
 	/**
 	 * @return the "trust exit code" flag
 	 */
 	@Override
-	public boolean isTrustExitCode() {
-		return trustExitCode == BooleanTriState.TRUE;
+	public BooleanTriState getTrustExitCode() {
+		return trustExitCode;
 	}
 
 	/**
-	 * @return the "trust exit code" option
+	 * @param trustExitCode
+	 *            the new "trust exit code" flag
 	 */
-	public BooleanTriState getTrustExitCode() {
-		return trustExitCode;
+	protected void setTrustExitCode(BooleanTriState trustExitCode) {
+		this.trustExitCode = trustExitCode;
 	}
 
+	/**
+	 * @param withBase
+	 *            not used, because user-defined merge tool can only define one
+	 *            cmd -> it must handle with and without base present (empty)
+	 * @return the tool command
+	 */
+	@Override
+	public String getCommand(boolean withBase) {
+		return getCommand();
+	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java
index e982a33b29..29c66f5165 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java
@@ -10,6 +10,7 @@
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
+
 package org.eclipse.jgit.lib;
 
 /**
@@ -66,7 +67,7 @@ public final class ConfigConstants {
 	public static final String CONFIG_KEY_TRUST_EXIT_CODE = "trustExitCode";
 
 	/**
-	 * The "cmd" key within "difftool.*." section
+	 * The "cmd" key within "difftool.*." or "mergetool.*." section
 	 *
 	 * @since 6.1
 	 */