Set core.precomposeunicode to true when creating repository on Mac

Java has no option but to use precomposed Unicode, so we should
state that when creating a new repository. Not that Java will use
precomposed unicode regardless of this setting, but this reduces
the risk of incompatibility with C Git.

Change-Id: I3779b75f76d2e2061c836cbc9b4b7c2ae0cf18f4

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

@@ -44,6 +44,9 @@ package org.eclipse.jgit.pgm;
 
 import static org.junit.Assert.assertArrayEquals;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.lib.CLIRepositoryTestCase;
 import org.eclipse.jgit.util.SystemReader;
@@ -62,12 +65,18 @@ public class ConfigTest extends CLIRepositoryTestCase {
 	public void testListConfig() throws Exception {
 		boolean isWindows = SystemReader.getInstance().getProperty("os.name")
 				.startsWith("Windows");
+		boolean isMac = SystemReader.getInstance().getProperty("os.name")
+				.equals("Mac OS X");
 
 		String[] output = execute("git config --list");
-		assertArrayEquals("expected default configuration", //
-				new String[] { "core.filemode=" + !isWindows, //
-						"core.logallrefupdates=true", //
-						"core.repositoryformatversion=0", //
-						"" /* ends with LF (last line empty) */}, output);
+		List<String> expect = new ArrayList<String>();
+		expect.add("core.filemode=" + !isWindows);
+		expect.add("core.logallrefupdates=true");
+		if (isMac)
+			expect.add("core.precomposeunicode=true");
+		expect.add("core.repositoryformatversion=0");
+		expect.add(""); // ends with LF (last line empty)
+		assertArrayEquals("expected default configuration", expect.toArray(),
+				output);
 	}
 }

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

@@ -178,4 +178,7 @@ public class ConfigConstants {
 
 	/** The "indexversion" key */
 	public static final String CONFIG_KEY_INDEXVERSION = "indexversion";
+
+	/** The "precomposeunicode" key */
+	public static final String CONFIG_KEY_PRECOMPOSEUNICODE = "precomposeunicode";
 }

org.eclipse.jgit/src/org/eclipse/jgit/storage/file/FileRepository.java

@@ -280,6 +280,10 @@ public class FileRepository extends Repository {
 					ConfigConstants.CONFIG_KEY_BARE, true);
 		cfg.setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
 				ConfigConstants.CONFIG_KEY_LOGALLREFUPDATES, !bare);
+		if (SystemReader.getInstance().isMacOS())
+			// Java has no other way
+			cfg.setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
+					ConfigConstants.CONFIG_KEY_PRECOMPOSEUNICODE, true);
 		cfg.save();
 	}