Support commit.template config property

Adds functionality to read the git commit.template property. The
template content is read either via a default encoding or, if present,
via encoding specified by i18n.commitEncoding property.

Bug: 446355

Change-Id: I0c45db98e324ddff26a7e0262835f259d6528a86
Signed-off-by: Julian Ruppel <julian.ruppel@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/ConfigTest.java

@@ -34,6 +34,7 @@ import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.text.MessageFormat;
@@ -50,6 +51,7 @@ import java.util.function.Consumer;
 import org.eclipse.jgit.api.MergeCommand.FastForwardMode;
 import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.junit.JGitTestUtil;
 import org.eclipse.jgit.junit.MockSystemReader;
 import org.eclipse.jgit.merge.MergeConfig;
 import org.eclipse.jgit.storage.file.FileBasedConfig;
@@ -1463,6 +1465,99 @@ public class ConfigTest {
 		assertEquals("tr   ue", parseEscapedValue("tr \\\r\n  ue"));
 	}
 
+	@Test
+	public void testCommitTemplateConfig()
+			throws ConfigInvalidException, IOException {
+		// no values defined nowhere
+		Config config = new Config(null);
+		assertNull(config.get(CommitConfig.KEY).getCommitTemplatePath());
+		assertNull(config.get(CommitConfig.KEY).getCommitTemplateContent());
+		File tempFile = tmp.newFile("testCommitTemplate-");
+		String templateContent = "content of the template";
+		JGitTestUtil.write(tempFile, templateContent);
+		// values are defined in the configuration
+		String expectedTemplatePath = tempFile.getPath();
+		config = parse("[commit]\n\ttemplate = " + expectedTemplatePath + "\n");
+		String templatePath = config.get(CommitConfig.KEY)
+				.getCommitTemplatePath();
+		String commitEncoding = config.get(CommitConfig.KEY)
+				.getCommitEncoding();
+		assertEquals(expectedTemplatePath, templatePath);
+		assertEquals(templateContent,
+				config.get(CommitConfig.KEY).getCommitTemplateContent());
+		assertNull("no commitEncoding has been set so it must be null",
+				commitEncoding);
+	}
+
+	@Test
+	public void testCommitTemplateEncoding()
+			throws ConfigInvalidException, IOException {
+		Config config = new Config(null);
+		File tempFile = tmp.newFile("testCommitTemplate-");
+		String templateContent = "content of the template";
+		JGitTestUtil.write(tempFile, templateContent);
+		String expectedTemplatePath = tempFile.getPath();
+		config = parse("[i18n]\n\tcommitEncoding = utf-8\n"
+				+ "[commit]\n\ttemplate = " + expectedTemplatePath + "\n");
+		assertEquals(templateContent,
+				config.get(CommitConfig.KEY).getCommitTemplateContent());
+		String commitEncoding = config.get(CommitConfig.KEY)
+				.getCommitEncoding();
+		assertEquals("commitEncoding has been set to utf-8 it must be utf-8",
+				"utf-8", commitEncoding);
+	}
+
+	@Test
+	public void testCommitTemplatePathInHomeDirecory()
+			throws ConfigInvalidException, IOException {
+		Config config = new Config(null);
+		File tempFile = tmp.newFile("testCommitTemplate-");
+		String templateContent = "content of the template";
+		JGitTestUtil.write(tempFile, templateContent);
+		// proper evaluation of the ~/ directory
+		String homeDir = System.getProperty("user.home");
+		File tempFileInHomeDirectory = File.createTempFile("fileInHomeFolder",
+				".tmp", new File(homeDir));
+		tempFileInHomeDirectory.deleteOnExit();
+		JGitTestUtil.write(tempFileInHomeDirectory, templateContent);
+		String expectedTemplatePath = tempFileInHomeDirectory.getPath()
+				.replace(homeDir, "~");
+		config = parse("[commit]\n\ttemplate = " + expectedTemplatePath + "\n");
+		String templatePath = config.get(CommitConfig.KEY)
+				.getCommitTemplatePath();
+		assertEquals(expectedTemplatePath, templatePath);
+		assertEquals(templateContent,
+				config.get(CommitConfig.KEY).getCommitTemplateContent());
+	}
+
+	@Test(expected = ConfigInvalidException.class)
+	public void testCommitTemplateWithInvalidEncoding()
+			throws ConfigInvalidException, IOException {
+		Config config = new Config(null);
+		File tempFile = tmp.newFile("testCommitTemplate-");
+		String templateContent = "content of the template";
+		JGitTestUtil.write(tempFile, templateContent);
+		config = parse("[i18n]\n\tcommitEncoding = invalidEcoding\n"
+				+ "[commit]\n\ttemplate = " + tempFile.getPath() + "\n");
+		config.get(CommitConfig.KEY).getCommitTemplateContent();
+	}
+
+	@Test(expected = FileNotFoundException.class)
+	public void testCommitTemplateWithInvalidPath()
+			throws ConfigInvalidException, IOException {
+		Config config = new Config(null);
+		File tempFile = tmp.newFile("testCommitTemplate-");
+		String templateContent = "content of the template";
+		JGitTestUtil.write(tempFile, templateContent);
+		// commit message encoding
+		String expectedTemplatePath = "nonExistingTemplate";
+		config = parse("[commit]\n\ttemplate = " + expectedTemplatePath + "\n");
+		String templatePath = config.get(CommitConfig.KEY)
+				.getCommitTemplatePath();
+		assertEquals(expectedTemplatePath, templatePath);
+		config.get(CommitConfig.KEY).getCommitTemplateContent();
+	}
+
 	private static void assertValueRoundTrip(String value)
 			throws ConfigInvalidException {
 		assertValueRoundTrip(value, value);

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -365,6 +365,7 @@ invalidBooleanValue=Invalid boolean value: {0}.{1}={2}
 invalidChannel=Invalid channel {0}
 invalidCommitParentNumber=Invalid commit parent number
 invalidDepth=Invalid depth: {0}
+invalidEncoding=Invalid encoding from git config i18n.commitEncoding: {0}
 invalidEncryption=Invalid encryption
 invalidExpandWildcard=ExpandFromSource on a refspec that can have mismatched wildcards does not make sense.
 invalidFilter=Invalid filter: {0}

org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java

@@ -393,6 +393,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String invalidChannel;
 	/***/ public String invalidCommitParentNumber;
 	/***/ public String invalidDepth;
+	/***/ public String invalidEncoding;
 	/***/ public String invalidEncryption;
 	/***/ public String invalidExpandWildcard;
 	/***/ public String invalidFilter;

org.eclipse.jgit/src/org/eclipse/jgit/lib/CommitConfig.java

@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2020 Julian Ruppel <julian.ruppel@sap.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.lib;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.nio.charset.IllegalCharsetNameException;
+import java.nio.charset.StandardCharsets;
+import java.nio.charset.UnsupportedCharsetException;
+import java.text.MessageFormat;
+import org.eclipse.jgit.annotations.Nullable;
+import org.eclipse.jgit.errors.ConfigInvalidException;
+import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.lib.Config.SectionParser;
+import org.eclipse.jgit.util.FS;
+import org.eclipse.jgit.util.IO;
+import org.eclipse.jgit.util.RawParseUtils;
+
+/**
+ * The standard "commit" configuration parameters.
+ *
+ * @since 5.12
+ */
+public class CommitConfig {
+	/**
+	 * Key for {@link Config#get(SectionParser)}.
+	 */
+	public static final Config.SectionParser<CommitConfig> KEY = CommitConfig::new;
+
+	private final static Charset DEFAULT_COMMIT_MESSAGE_ENCODING = StandardCharsets.UTF_8;
+
+	private String i18nCommitEncoding;
+
+	private String commitTemplatePath;
+
+	private CommitConfig(Config rc) {
+		commitTemplatePath = rc.getString(ConfigConstants.CONFIG_COMMIT_SECTION,
+				null, ConfigConstants.CONFIG_KEY_COMMIT_TEMPLATE);
+		i18nCommitEncoding = rc.getString(ConfigConstants.CONFIG_SECTION_I18N,
+				null, ConfigConstants.CONFIG_KEY_COMMIT_ENCODING);
+	}
+
+	/**
+	 * Get the path to the commit template as defined in the git
+	 * {@code commit.template} property.
+	 *
+	 * @return the path to commit template or {@code null} if not present.
+	 */
+	@Nullable
+	public String getCommitTemplatePath() {
+		return commitTemplatePath;
+	}
+
+	/**
+	 * Get the encoding of the commit as defined in the git
+	 * {@code i18n.commitEncoding} property.
+	 *
+	 * @return the encoding or {@code null} if not present.
+	 */
+	@Nullable
+	public String getCommitEncoding() {
+		return i18nCommitEncoding;
+	}
+
+	/**
+	 * Get the content to the commit template as defined in
+	 * {@code commit.template}. If no {@code i18n.commitEncoding} is specified,
+	 * UTF-8 fallback is used.
+	 *
+	 * @return content of the commit template or {@code null} if not present.
+	 * @throws IOException
+	 *             if the template file can not be read
+	 * @throws FileNotFoundException
+	 *             if the template file does not exists
+	 * @throws ConfigInvalidException
+	 *             if a {@code commitEncoding} is specified and is invalid
+	 */
+	@Nullable
+	public String getCommitTemplateContent()
+			throws FileNotFoundException, IOException, ConfigInvalidException {
+
+		if (commitTemplatePath != null) {
+			Charset commitMessageEncoding = getEncoding();
+
+			File commitTemplateFile;
+			if (commitTemplatePath.startsWith("~/")) { //$NON-NLS-1$
+				commitTemplateFile = FS.DETECTED.resolve(FS.DETECTED.userHome(),
+						commitTemplatePath.substring(2));
+			} else {
+				commitTemplateFile = FS.DETECTED.resolve(null,
+						commitTemplatePath);
+			}
+			return RawParseUtils.decode(commitMessageEncoding,
+					IO.readFully(commitTemplateFile));
+		}
+		return null;
+	}
+
+	private Charset getEncoding() throws ConfigInvalidException {
+		Charset commitMessageEncoding = DEFAULT_COMMIT_MESSAGE_ENCODING;
+
+		if (i18nCommitEncoding != null) {
+			try {
+				commitMessageEncoding = Charset.forName(i18nCommitEncoding);
+			} catch (IllegalCharsetNameException
+					| UnsupportedCharsetException e) {
+				throw new ConfigInvalidException(
+						MessageFormat.format(JGitText.get().invalidEncoding,
+								i18nCommitEncoding),
+						e);
+			}
+		}
+		return commitMessageEncoding;
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java

@@ -124,6 +124,13 @@ public final class ConfigConstants {
 	 */
 	public static final String CONFIG_COMMIT_SECTION = "commit";
 
+	/**
+	 * The "template" key
+	 *
+	 * @since 5.12
+	 */
+	public static final String CONFIG_KEY_COMMIT_TEMPLATE = "template";
+
 	/**
 	 * The "tag" section
 	 *
@@ -517,6 +524,13 @@ public final class ConfigConstants {
 	 */
 	public static final String CONFIG_SECTION_I18N = "i18n";
 
+	/**
+	 * The "commitEncoding" key
+	 *
+	 * @since 5.12
+	 */
+	public static final String CONFIG_KEY_COMMIT_ENCODING = "commitEncoding";
+
 	/**
 	 * The "logOutputEncoding" key
 	 *