Add mergetool merge feature (execute external tool)

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

* implement mergetool merge function (execute external tool)
* add ExecutionResult and commandExecutionError to ToolException
* handle "base not present" case (empty or null base file path)
* handle deleted (rm) and modified (add) conflicts
* handle settings
 * keepBackup
 * keepTemporaries
 * writeToTemp

Bug: 356832
Change-Id: Id323c2fcb1c24d12ceb299801df8bac51a6d463f
Signed-off-by: Andre Bossert <andre.bossert@siemens.com>

3 files changed, 364 insertions, 51 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 017a5d994f..dc34c0d67b 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
@@ -16,6 +16,7 @@ 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.fail;
 
+import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -30,7 +31,7 @@ import org.junit.Test;
 /**
  * Testing the {@code difftool} command.
  */
-public class DiffToolTest extends ExternalToolTestCase {
+public class DiffToolTest extends ToolTestCase {
 
 	private static final String DIFF_TOOL = CONFIG_DIFFTOOL_SECTION;
 
@@ -41,6 +42,46 @@ public class DiffToolTest extends ExternalToolTestCase {
 		configureEchoTool(TOOL_NAME);
 	}
 
+	@Test
+	public void testToolWithPrompt() throws Exception {
+		String[] inputLines = {
+				"y", // accept launching diff tool
+				"y", // accept launching diff tool
+		};
+
+		RevCommit commit = createUnstagedChanges();
+		List<DiffEntry> changes = getRepositoryChanges(commit);
+		String[] expectedOutput = getExpectedCompareOutput(changes);
+
+		String option = "--tool";
+
+		InputStream inputStream = createInputStream(inputLines);
+		assertArrayOfLinesEquals("Incorrect output for option: " + option,
+				expectedOutput, runAndCaptureUsingInitRaw(inputStream,
+						DIFF_TOOL, "--prompt", option, TOOL_NAME));
+	}
+
+	@Test
+	public void testToolAbortLaunch() throws Exception {
+		String[] inputLines = {
+				"y", // accept launching diff tool
+				"n", // don't launch diff tool
+		};
+
+		RevCommit commit = createUnstagedChanges();
+		List<DiffEntry> changes = getRepositoryChanges(commit);
+		int abortIndex = 1;
+		String[] expectedOutput = getExpectedAbortOutput(changes, abortIndex);
+
+		String option = "--tool";
+
+		InputStream inputStream = createInputStream(inputLines);
+		assertArrayOfLinesEquals("Incorrect output for option: " + option,
+				expectedOutput,
+				runAndCaptureUsingInitRaw(inputStream, DIFF_TOOL, "--prompt", option,
+						TOOL_NAME));
+	}
+
 	@Test(expected = Die.class)
 	public void testNotDefinedTool() throws Exception {
 		createUnstagedChanges();
@@ -53,7 +94,7 @@ public class DiffToolTest extends ExternalToolTestCase {
 	public void testTool() throws Exception {
 		RevCommit commit = createUnstagedChanges();
 		List<DiffEntry> changes = getRepositoryChanges(commit);
-		String[] expectedOutput = getExpectedToolOutput(changes);
+		String[] expectedOutput = getExpectedToolOutputNoPrompt(changes);
 
 		String[] options = {
 				"--tool",
@@ -72,7 +113,7 @@ public class DiffToolTest extends ExternalToolTestCase {
 	public void testToolTrustExitCode() throws Exception {
 		RevCommit commit = createUnstagedChanges();
 		List<DiffEntry> changes = getRepositoryChanges(commit);
-		String[] expectedOutput = getExpectedToolOutput(changes);
+		String[] expectedOutput = getExpectedToolOutputNoPrompt(changes);
 
 		String[] options = { "--tool", "-t", };
 
@@ -87,7 +128,7 @@ public class DiffToolTest extends ExternalToolTestCase {
 	public void testToolNoGuiNoPromptNoTrustExitcode() throws Exception {
 		RevCommit commit = createUnstagedChanges();
 		List<DiffEntry> changes = getRepositoryChanges(commit);
-		String[] expectedOutput = getExpectedToolOutput(changes);
+		String[] expectedOutput = getExpectedToolOutputNoPrompt(changes);
 
 		String[] options = { "--tool", "-t", };
 
@@ -103,7 +144,7 @@ public class DiffToolTest extends ExternalToolTestCase {
 	public void testToolCached() throws Exception {
 		RevCommit commit = createStagedChanges();
 		List<DiffEntry> changes = getRepositoryChanges(commit);
-		String[] expectedOutput = getExpectedToolOutput(changes);
+		String[] expectedOutput = getExpectedToolOutputNoPrompt(changes);
 
 		String[] options = { "--cached", "--staged", };
 
@@ -118,7 +159,8 @@ public class DiffToolTest extends ExternalToolTestCase {
 	public void testToolHelp() throws Exception {
 		CommandLineDiffTool[] defaultTools = CommandLineDiffTool.values();
 		List<String> expectedOutput = new ArrayList<>();
-		expectedOutput.add("git difftool --tool=<tool> may be set to one of the following:");
+		expectedOutput.add(
+				"'git difftool --tool=<tool>' may be set to one of the following:");
 		for (CommandLineDiffTool defaultTool : defaultTools) {
 			String toolName = defaultTool.name();
 			expectedOutput.add(toolName);
@@ -159,7 +201,7 @@ public class DiffToolTest extends ExternalToolTestCase {
 				String.valueOf(false));
 	}
 
-	private String[] getExpectedToolOutput(List<DiffEntry> changes) {
+	private static String[] getExpectedToolOutputNoPrompt(List<DiffEntry> changes) {
 		String[] expectedToolOutput = new String[changes.size()];
 		for (int i = 0; i < changes.size(); ++i) {
 			DiffEntry change = changes.get(i);
@@ -169,4 +211,36 @@ public class DiffToolTest extends ExternalToolTestCase {
 		}
 		return expectedToolOutput;
 	}
+
+	private static String[] getExpectedCompareOutput(List<DiffEntry> changes) {
+		List<String> expected = new ArrayList<>();
+		int n = changes.size();
+		for (int i = 0; i < n; ++i) {
+			DiffEntry change = changes.get(i);
+			String newPath = change.getNewPath();
+			expected.add(
+					"Viewing (" + (i + 1) + "/" + n + "): '" + newPath + "'");
+			expected.add("Launch '" + TOOL_NAME + "' [Y/n]?");
+			expected.add(newPath);
+		}
+		return expected.toArray(new String[0]);
+	}
+
+	private static String[] getExpectedAbortOutput(List<DiffEntry> changes,
+			int abortIndex) {
+		List<String> expected = new ArrayList<>();
+		int n = changes.size();
+		for (int i = 0; i < n; ++i) {
+			DiffEntry change = changes.get(i);
+			String newPath = change.getNewPath();
+			expected.add(
+					"Viewing (" + (i + 1) + "/" + n + "): '" + newPath + "'");
+			expected.add("Launch '" + TOOL_NAME + "' [Y/n]?");
+			if (i == abortIndex) {
+				break;
+			}
+			expected.add(newPath);
+		}
+		return expected.toArray(new String[0]);
+	}
 }
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
index 32cd60415e..2e50f09081 100644
--- 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
@@ -15,6 +15,7 @@ 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.io.InputStream;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -27,7 +28,7 @@ import org.junit.Test;
 /**
  * Testing the {@code mergetool} command.
  */
-public class MergeToolTest extends ExternalToolTestCase {
+public class MergeToolTest extends ToolTestCase {
 
 	private static final String MERGE_TOOL = CONFIG_MERGETOOL_SECTION;
 
@@ -39,38 +40,122 @@ public class MergeToolTest extends ExternalToolTestCase {
 	}
 
 	@Test
-	public void testTool() throws Exception {
-		createMergeConflict();
-		String[] expectedOutput = getExpectedToolOutput();
+	public void testAbortMerge() throws Exception {
+		String[] inputLines = {
+				"y", // start tool for merge resolution
+				"n", // don't accept merge tool result
+				"n", // don't continue resolution
+		};
+		String[] conflictingFilenames = createMergeConflict();
+		int abortIndex = 1;
+		String[] expectedOutput = getExpectedAbortMergeOutput(
+				conflictingFilenames,
+				abortIndex);
+
+		String option = "--tool";
+
+		InputStream inputStream = createInputStream(inputLines);
+		assertArrayOfLinesEquals("Incorrect output for option: " + option,
+				expectedOutput, runAndCaptureUsingInitRaw(inputStream,
+						MERGE_TOOL, "--prompt", option, TOOL_NAME));
+	}
 
-		String[] options = {
-				"--tool",
-				"-t",
+	@Test
+	public void testAbortLaunch() throws Exception {
+		String[] inputLines = {
+				"n", // abort merge tool launch
 		};
+		String[] conflictingFilenames = createMergeConflict();
+		String[] expectedOutput = getExpectedAbortLaunchOutput(
+				conflictingFilenames);
 
-		for (String option : options) {
-			assertArrayOfLinesEquals("Incorrect output for option: " + option,
-					expectedOutput,
-					runAndCaptureUsingInitRaw(MERGE_TOOL, option,
-							TOOL_NAME));
-		}
+		String option = "--tool";
+
+		InputStream inputStream = createInputStream(inputLines);
+		assertArrayOfLinesEquals("Incorrect output for option: " + option,
+				expectedOutput, runAndCaptureUsingInitRaw(inputStream,
+						MERGE_TOOL, "--prompt", option, TOOL_NAME));
 	}
 
 	@Test
-	public void testToolNoGuiNoPrompt() throws Exception {
-		createMergeConflict();
-		String[] expectedOutput = getExpectedToolOutput();
+	public void testMergeConflict() throws Exception {
+		String[] inputLines = {
+				"y", // start tool for merge resolution
+				"y", // accept merge result as successful
+				"y", // start tool for merge resolution
+				"y", // accept merge result as successful
+		};
+		String[] conflictingFilenames = createMergeConflict();
+		String[] expectedOutput = getExpectedMergeConflictOutput(
+				conflictingFilenames);
+
+		String option = "--tool";
+
+		InputStream inputStream = createInputStream(inputLines);
+		assertArrayOfLinesEquals("Incorrect output for option: " + option,
+				expectedOutput, runAndCaptureUsingInitRaw(inputStream,
+						MERGE_TOOL, "--prompt", option, TOOL_NAME));
+	}
+
+	@Test
+	public void testDeletedConflict() throws Exception {
+		String[] inputLines = {
+				"d", // choose delete option to resolve conflict
+				"m", // choose merge option to resolve conflict
+		};
+		String[] conflictingFilenames = createDeletedConflict();
+		String[] expectedOutput = getExpectedDeletedConflictOutput(
+				conflictingFilenames);
+
+		String option = "--tool";
+
+		InputStream inputStream = createInputStream(inputLines);
+		assertArrayOfLinesEquals("Incorrect output for option: " + option,
+				expectedOutput, runAndCaptureUsingInitRaw(inputStream,
+						MERGE_TOOL, "--prompt", option, TOOL_NAME));
+	}
+
+	@Test
+	public void testNoConflict() throws Exception {
+		createStagedChanges();
+		String[] expectedOutput = { "No files need merging" };
 
 		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));
+					expectedOutput,
+					runAndCaptureUsingInitRaw(MERGE_TOOL, option, TOOL_NAME));
 		}
 	}
 
 	@Test
+	public void testMergeConflictNoPrompt() throws Exception {
+		String[] conflictingFilenames = createMergeConflict();
+		String[] expectedOutput = getExpectedMergeConflictOutputNoPrompt(
+				conflictingFilenames);
+
+		String option = "--tool";
+
+		assertArrayOfLinesEquals("Incorrect output for option: " + option,
+				expectedOutput,
+				runAndCaptureUsingInitRaw(MERGE_TOOL, option, TOOL_NAME));
+	}
+
+	@Test
+	public void testMergeConflictNoGuiNoPrompt() throws Exception {
+		String[] conflictingFilenames = createMergeConflict();
+		String[] expectedOutput = getExpectedMergeConflictOutputNoPrompt(
+				conflictingFilenames);
+
+		String option = "--tool";
+
+		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<>();
@@ -87,8 +172,7 @@ public class MergeToolTest extends ExternalToolTestCase {
 		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.",
-		};
+				"environment. If run in a terminal-only session, they will fail.", };
 		expectedOutput.addAll(Arrays.asList(userDefinedToolsHelp));
 
 		String option = "--tool-help";
@@ -116,21 +200,111 @@ public class MergeToolTest extends ExternalToolTestCase {
 				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);
+	private static String[] getExpectedMergeConflictOutputNoPrompt(
+			String[] conflictFilenames) {
+		List<String> expected = new ArrayList<>();
+		expected.add("Merging:");
+		for (String conflictFilename : conflictFilenames) {
+			expected.add(conflictFilename);
+		}
+		for (String conflictFilename : conflictFilenames) {
+			expected.add("Normal merge conflict for '" + conflictFilename
+					+ "':");
+			expected.add("{local}: modified file");
+			expected.add("{remote}: modified file");
+			expected.add(conflictFilename);
+			expected.add(conflictFilename + " seems unchanged.");
+		}
+		return expected.toArray(new String[0]);
+	}
+
+	private static String[] getExpectedAbortLaunchOutput(
+			String[] conflictFilenames) {
+		List<String> expected = new ArrayList<>();
+		expected.add("Merging:");
+		for (String conflictFilename : conflictFilenames) {
+			expected.add(conflictFilename);
+		}
+		if (conflictFilenames.length > 1) {
+			String conflictFilename = conflictFilenames[0];
+			expected.add(
+					"Normal merge conflict for '" + conflictFilename + "':");
+			expected.add("{local}: modified file");
+			expected.add("{remote}: modified file");
+			expected.add("Hit return to start merge resolution tool ("
+					+ TOOL_NAME + "):");
+		}
+		return expected.toArray(new String[0]);
+	}
+
+	private static String[] getExpectedAbortMergeOutput(
+			String[] conflictFilenames, int abortIndex) {
+		List<String> expected = new ArrayList<>();
+		expected.add("Merging:");
+		for (String conflictFilename : conflictFilenames) {
+			expected.add(conflictFilename);
+		}
+		for (int i = 0; i < conflictFilenames.length; ++i) {
+			if (i == abortIndex) {
+				break;
+			}
+
+			String conflictFilename = conflictFilenames[i];
+			expected.add(
+					"Normal merge conflict for '" + conflictFilename + "':");
+			expected.add("{local}: modified file");
+			expected.add("{remote}: modified file");
+			expected.add("Hit return to start merge resolution tool ("
+					+ TOOL_NAME + "): " + conflictFilename);
+			expected.add(conflictFilename + " seems unchanged.");
+			expected.add("Was the merge successful [y/n]?");
+			if (i < conflictFilenames.length - 1) {
+				expected.add(
+						"\tContinue merging other unresolved paths [y/n]?");
+			}
+		}
+		return expected.toArray(new String[0]);
+	}
+
+	private static String[] getExpectedMergeConflictOutput(
+			String[] conflictFilenames) {
+		List<String> expected = new ArrayList<>();
+		expected.add("Merging:");
+		for (String conflictFilename : conflictFilenames) {
+			expected.add(conflictFilename);
+		}
+		for (int i = 0; i < conflictFilenames.length; ++i) {
+			String conflictFilename = conflictFilenames[i];
+			expected.add("Normal merge conflict for '" + conflictFilename
+					+ "':");
+			expected.add("{local}: modified file");
+			expected.add("{remote}: modified file");
+			expected.add("Hit return to start merge resolution tool ("
+					+ TOOL_NAME + "): " + conflictFilename);
+			expected.add(conflictFilename + " seems unchanged.");
+			expected.add("Was the merge successful [y/n]?");
+			if (i < conflictFilenames.length - 1) {
+				// expected.add(
+				// "\tContinue merging other unresolved paths [y/n]?");
+			}
+		}
+		return expected.toArray(new String[0]);
+	}
+
+	private static String[] getExpectedDeletedConflictOutput(
+			String[] conflictFilenames) {
+		List<String> expected = new ArrayList<>();
+		expected.add("Merging:");
+		for (String mergeConflictFilename : conflictFilenames) {
+			expected.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 + "'...");
+		for (int i = 0; i < conflictFilenames.length; ++i) {
+			String conflictFilename = conflictFilenames[i];
+			expected.add(conflictFilename + " seems unchanged.");
+			expected.add("{local}: deleted");
+			expected.add("{remote}: modified file");
+			expected.add("Use (m)odified or (d)eleted file, or (a)bort?");
 		}
-		return expectedOutput.toArray(new String[0]);
+		return expected.toArray(new String[0]);
 	}
 }
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/ToolTestCase.java
index e10b13efb1..d13eeb7e4d 100644
--- a/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/ExternalToolTestCase.java
+++ b/org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/ToolTestCase.java
@@ -11,10 +11,14 @@ package org.eclipse.jgit.pgm;
 
 import static org.junit.Assert.assertEquals;
 
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
 import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
+import java.util.stream.Collectors;
 
-import org.eclipse.jgit.api.CherryPickResult;
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.diff.DiffEntry;
 import org.eclipse.jgit.lib.CLIRepositoryTestCase;
@@ -29,7 +33,7 @@ import org.kohsuke.args4j.Argument;
 /**
  * Base test case for the {@code difftool} and {@code mergetool} commands.
  */
-public abstract class ExternalToolTestCase extends CLIRepositoryTestCase {
+public abstract class ToolTestCase extends CLIRepositoryTestCase {
 
 	public static class GitCliJGitWrapperParser {
 		@Argument(index = 0, metaVar = "metaVar_command", required = true, handler = SubcommandHandler.class)
@@ -56,6 +60,12 @@ public abstract class ExternalToolTestCase extends CLIRepositoryTestCase {
 
 	protected String[] runAndCaptureUsingInitRaw(String... args)
 			throws Exception {
+		InputStream inputStream = null; // no input stream
+		return runAndCaptureUsingInitRaw(inputStream, args);
+	}
+
+	protected String[] runAndCaptureUsingInitRaw(InputStream inputStream,
+			String... args) throws Exception {
 		CLIGitCommand.Result result = new CLIGitCommand.Result();
 
 		GitCliJGitWrapperParser bean = new GitCliJGitWrapperParser();
@@ -63,7 +73,7 @@ public abstract class ExternalToolTestCase extends CLIRepositoryTestCase {
 		clp.parseArgument(args);
 
 		TextBuiltin cmd = bean.subcommand;
-		cmd.initRaw(db, null, null, result.out, result.err);
+		cmd.initRaw(db, null, inputStream, result.out, result.err);
 		cmd.execute(bean.arguments.toArray(new String[bean.arguments.size()]));
 		if (cmd.getOutputWriter() != null) {
 			cmd.getOutputWriter().flush();
@@ -71,28 +81,73 @@ public abstract class ExternalToolTestCase extends CLIRepositoryTestCase {
 		if (cmd.getErrorWriter() != null) {
 			cmd.getErrorWriter().flush();
 		}
+
+		List<String> errLines = result.errLines().stream()
+				.filter(l -> !l.isBlank()) // we care only about error messages
+				.collect(Collectors.toList());
+		assertEquals("Expected no standard error output from tool",
+				Collections.EMPTY_LIST.toString(), errLines.toString());
+
 		return result.outLines().toArray(new String[0]);
 	}
 
-	protected CherryPickResult createMergeConflict() throws Exception {
+	protected String[] createMergeConflict() throws Exception {
+		// create files on initial branch
+		git.checkout().setName(TEST_BRANCH_NAME).call();
 		writeTrashFile("a", "Hello world a");
 		writeTrashFile("b", "Hello world b");
 		git.add().addFilepattern(".").call();
 		git.commit().setMessage("files a & b added").call();
+		// create another branch and change files
+		git.branchCreate().setName("branch_1").call();
+		git.checkout().setName("branch_1").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();
+		RevCommit commit1 = git.commit()
+				.setMessage("files a & b modified commit 1").call();
+		// checkout initial branch
 		git.checkout().setName(TEST_BRANCH_NAME).call();
+		// create another branch and change files
+		git.branchCreate().setName("branch_2").call();
+		git.checkout().setName("branch_2").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.commit().setMessage("files a & b modified commit 2").call();
+		// cherry-pick conflicting changes
+		git.cherryPick().include(commit1).call();
+		String[] conflictingFilenames = { "a", "b" };
+		return conflictingFilenames;
+	}
+
+	protected String[] createDeletedConflict() throws Exception {
+		// create files on initial branch
+		git.checkout().setName(TEST_BRANCH_NAME).call();
+		writeTrashFile("a", "Hello world a");
+		writeTrashFile("b", "Hello world b");
+		git.add().addFilepattern(".").call();
+		git.commit().setMessage("files a & b added").call();
+		// create another branch and change files
+		git.branchCreate().setName("branch_1").call();
+		git.checkout().setName("branch_1").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 modified commit 1").call();
+		// checkout initial branch
+		git.checkout().setName(TEST_BRANCH_NAME).call();
+		// create another branch and change files
 		git.branchCreate().setName("branch_2").call();
-		CherryPickResult result = git.cherryPick().include(commit1).call();
-		return result;
+		git.checkout().setName("branch_2").call();
+		git.rm().addFilepattern("a").call();
+		git.rm().addFilepattern("b").call();
+		git.commit().setMessage("files a & b deleted commit 2").call();
+		// cherry-pick conflicting changes
+		git.cherryPick().include(commit1).call();
+		String[] conflictingFilenames = { "a", "b" };
+		return conflictingFilenames;
 	}
 
 	protected RevCommit createUnstagedChanges() throws Exception {
@@ -121,6 +176,16 @@ public abstract class ExternalToolTestCase extends CLIRepositoryTestCase {
 		return changes;
 	}
 
+	protected static InputStream createInputStream(String[] inputLines) {
+		return createInputStream(Arrays.asList(inputLines));
+	}
+
+	protected static InputStream createInputStream(List<String> inputLines) {
+		String input = String.join(System.lineSeparator(), inputLines);
+		InputStream inputStream = new ByteArrayInputStream(input.getBytes());
+		return inputStream;
+	}
+
 	protected static void assertArrayOfLinesEquals(String failMessage,
 			String[] expected, String[] actual) {
 		assertEquals(failMessage, toString(expected), toString(actual));