Handle escaped CR-LF in git config files

Canonical git treats CR-LF in config files as LF.[1][2] JGit does so,
too, except when escaped as a line continuation. Correct this and
treat the sequence \-CR-LF as a line continuation.

[1] https://github.com/git/git/commit/db2c075d9
[2] https://github.com/git/git/blob/v2.21.0/config.c#L485

Bug: 545850
Change-Id: I51e7378a22c21b3baa3701163c423d04c900af5a
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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

@@ -1457,6 +1457,41 @@ public class ConfigTest {
 		parse("[foo \"bar\" ]\nfoo=bar\n");
 	}
 
+	@Test
+	public void testCrLf() throws ConfigInvalidException {
+		assertEquals("true", parseEscapedValue("true\r\n"));
+	}
+
+	@Test
+	public void testLfContinuation() throws ConfigInvalidException {
+		assertEquals("true", parseEscapedValue("tr\\\nue"));
+	}
+
+	@Test
+	public void testCrCharContinuation() throws ConfigInvalidException {
+		expectedEx.expect(ConfigInvalidException.class);
+		expectedEx.expectMessage("Bad escape: \\u000d");
+		parseEscapedValue("tr\\\rue");
+	}
+
+	@Test
+	public void testCrEOFContinuation() throws ConfigInvalidException {
+		expectedEx.expect(ConfigInvalidException.class);
+		expectedEx.expectMessage("Bad escape: \\u000d");
+		parseEscapedValue("tr\\\r");
+	}
+
+	@Test
+	public void testCrLfContinuation() throws ConfigInvalidException {
+		assertEquals("true", parseEscapedValue("tr\\\r\nue"));
+	}
+
+	@Test
+	public void testWhitespaceContinuation() throws ConfigInvalidException {
+		assertEquals("tr   ue", parseEscapedValue("tr \\\n  ue"));
+		assertEquals("tr   ue", parseEscapedValue("tr \\\r\n  ue"));
+	}
+
 	private static void assertValueRoundTrip(String value)
 			throws ConfigInvalidException {
 		assertValueRoundTrip(value, value);

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

@@ -1413,11 +1413,23 @@ public class Config {
 				case '"':
 					value.append('"');
 					continue;
+				case '\r': {
+					int next = in.read();
+					if (next == '\n') {
+						continue; // CR-LF
+					} else if (next >= 0) {
+						in.reset();
+					}
+					break;
+				}
 				default:
-					throw new ConfigInvalidException(MessageFormat.format(
-							JGitText.get().badEscape,
-							Character.valueOf(((char) c))));
+					break;
 				}
+				throw new ConfigInvalidException(
+						MessageFormat.format(JGitText.get().badEscape,
+								Character.isAlphabetic(c)
+										? Character.valueOf(((char) c))
+										: toUnicodeLiteral(c)));
 			}
 
 			if ('"' == c) {
@@ -1430,6 +1442,11 @@ public class Config {
 		return value.length() > 0 ? value.toString() : null;
 	}
 
+	private static String toUnicodeLiteral(int c) {
+		return String.format("\\u%04x", //$NON-NLS-1$
+				Integer.valueOf(c));
+	}
+
 	/**
 	 * Parses a section of the configuration into an application model object.
 	 * <p>