PersonIdent: Strip some special chars from external strings

The special characters <> and '\n' interfere with parsing of
identities. C git strips these special characters, so we should too.

Rather than allocating extra strings by calling String#trim(), add a
few lines to our sanitization method to perform the same trimming as
described in String's Javadoc.

Change-Id: I96edcb93a2fc194ee354d60566d352299742a52f

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/T0001_PersonIdentTest.java

@@ -89,14 +89,47 @@ public class T0001_PersonIdentTest {
 
 	@Test
 	public void testToExternalStringTrimsNameAndEmail() throws Exception {
-		PersonIdent personIdent = new PersonIdent("  A U Thor  ",
+		PersonIdent personIdent = new PersonIdent(" \u0010A U Thor  ",
-				"  author@example.com  ");
+				"  author@example.com \u0009");
 
-		assertEquals("  A U Thor  ", personIdent.getName());
+		assertEquals(" \u0010A U Thor  ", personIdent.getName());
-		assertEquals("  author@example.com  ", personIdent.getEmailAddress());
+		assertEquals("  author@example.com \u0009", personIdent.getEmailAddress());
 
 		String externalString = personIdent.toExternalString();
 		assertTrue(externalString.startsWith("A U Thor <author@example.com>"));
 	}
 
+	@Test
+	public void testToExternalStringTrimsAllWhitespace() {
+		String ws = "  \u0001 \n ";
+		PersonIdent personIdent = new PersonIdent(ws, ws);
+		assertEquals(ws, personIdent.getName());
+		assertEquals(ws, personIdent.getEmailAddress());
+
+		String externalString = personIdent.toExternalString();
+		assertTrue(externalString.startsWith(" <>"));
+	}
+
+	@Test
+	public void testToExternalStringTrimsOtherBadCharacters() {
+		String name = " Foo\r\n<Bar> ";
+		String email = " Baz>\n\u1234<Quux ";
+		PersonIdent personIdent = new PersonIdent(name, email);
+		assertEquals(name, personIdent.getName());
+		assertEquals(email, personIdent.getEmailAddress());
+
+		String externalString = personIdent.toExternalString();
+		assertTrue(externalString.startsWith("Foo\rBar <Baz\u1234Quux>"));
+	}
+
+	@Test
+	public void testEmptyNameAndEmail() {
+		PersonIdent personIdent = new PersonIdent("", "");
+		assertEquals("", personIdent.getName());
+		assertEquals("", personIdent.getEmailAddress());
+
+		String externalString = personIdent.toExternalString();
+		assertTrue(externalString.startsWith(" <>"));
+	}
+
 }

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

@@ -111,6 +111,43 @@ public class PersonIdent implements Serializable {
 		r.append(offsetMins);
 	}
 
+	/**
+	 * Sanitize the given string for use in an identity and append to output.
+	 * <p>
+	 * Trims whitespace from both ends and special characters {@code \n < >} that
+	 * interfere with parsing; appends all other characters to the output.
+	 * Analogous to the C git function {@code strbuf_addstr_without_crud}.
+	 *
+	 * @param r
+	 *            string builder to append to.
+	 * @param str
+	 *            input string.
+	 */
+	private static void appendSanitized(StringBuilder r, String str) {
+		// Trim any whitespace less than \u0020 as in String#trim().
+		int i = 0;
+		while (i < str.length() && str.charAt(i) <= ' ') {
+			i++;
+		}
+		int end = str.length();
+		while (end > i && str.charAt(end - 1) <= ' ') {
+			end--;
+		}
+
+		for (; i < end; i++) {
+			char c = str.charAt(i);
+			switch (c) {
+				case '\n':
+				case '<':
+				case '>':
+					continue;
+				default:
+					r.append(c);
+					break;
+			}
+		}
+	}
+
 	private final String name;
 
 	private final String emailAddress;
@@ -305,9 +342,9 @@ public class PersonIdent implements Serializable {
 	 */
 	public String toExternalString() {
 		final StringBuilder r = new StringBuilder();
-		r.append(getName().trim());
+		appendSanitized(r, getName());
 		r.append(" <"); //$NON-NLS-1$
-		r.append(getEmailAddress().trim());
+		appendSanitized(r, getEmailAddress());
 		r.append("> "); //$NON-NLS-1$
 		r.append(when / 1000);
 		r.append(' ');