[JGIT PATCH v3 0/23] Implementation of a file tree iteration using ignore rules.

@@ -201,8 +201,9 @@ public final class Constants {
 
 	/**
 	 * Convert an OBJ_* type constant to a TYPE_* type constant.
-	 *
-	 * @param typeCode the type code, from a pack representation.
+	 * 
+	 * @param typeCode
+	 *            the type code, from a pack representation.
 	 * @return the canonical string name of this type.
 	 */
 	public static String typeString(final int typeCode) {

@@ -223,10 +224,11 @@ public final class Constants {
 	/**
 	 * Convert an OBJ_* type constant to an ASCII encoded string constant.
 	 * <p>
-	 * The ASCII encoded string is often the canonical representation of
-	 * the type within a loose object header, or within a tag header.
-	 *
-	 * @param typeCode the type code, from a pack representation.
+	 * The ASCII encoded string is often the canonical representation of the
+	 * type within a loose object header, or within a tag header.
+	 * 
+	 * @param typeCode
+	 *            the type code, from a pack representation.
 	 * @return the canonical ASCII encoded name of this type.
 	 */
 	public static byte[] encodedTypeString(final int typeCode) {

@@ -182,6 +182,12 @@ public final class Constants {
 	public static final String TAGS_PREFIX = "refs/tags";
 
 	/**
+	 * The name of the repository directory in the project directory. Project
+	 * directory means here the tree under version control.
+	 */
+	public static final String REPOSITORY_DIRECTORY_NAME = ".git";
+
+	/**
 	 * Create a new digest function for objects.
 	 * 
 	 * @return a new digest object.

@@ -0,0 +1,61 @@
+/*
+ *  Copyright (C) 2008 Florian Köberle
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public
+ *  License, version 2, as published by the Free Software Foundation.
+ *
+ *  This library is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public
+ *  License along with this library; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301
+ */
+package org.spearce.jgit.treewalk.rules;
+
+/**
+ * A Rule defines what to do with a files which match a specified
+ * {@link FilePattern}.
+ */
+public class Rule {
+	private boolean ignoreAtMatch;
+
+	private FilePattern pattern;
+
+	/**
+	 * 
+	 * @param ignoreAtMatch
+	 *            defines if the rules ignores or accepts at a match.
+	 * @param pattern
+	 *            the pattern used to test if a file matches.
+	 */
+	Rule(boolean ignoreAtMatch, FilePattern pattern) {
+		this.ignoreAtMatch = ignoreAtMatch;
+		this.pattern = pattern;
+	}
+
+	FilePattern getPattern() {
+		return pattern;
+	}
+
+	boolean isIgnoreAtMatch() {
+		return ignoreAtMatch;
+	}
+
+	Rule getRuleForSubDirectory(String directoryName) {
+		final FilePattern subPattern = pattern
+				.getPatternForSubDirectory(directoryName);
+		if (subPattern == pattern) {
+			return this;
+		}
+		return new Rule(ignoreAtMatch, subPattern);
+	}
+
+	boolean isSameForSubDirectories() {
+		return pattern.isSameForSubDirectories();
+	}
+
+}

@@ -0,0 +1,99 @@
+/*
+ *  Copyright (C) 2008 Florian Köberle
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public
+ *  License, version 2, as published by the Free Software Foundation.
+ *
+ *  This library is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public
+ *  License along with this library; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301
+ */
+package org.spearce.jgit.treewalk.rules;
+
+/**
+ * A {@link Rules} instances defines ignore or do not ignore rules for files in
+ * a directory. It can't directly be used to match files in sub directories, but
+ * provides a method {@link #getRulesForSubDirectory}.
+ * 
+ */
+public interface Rules {
+
+	/**
+	 * Provides the instance of {@link IgnoreAllRules}.
+	 */
+	public static final Rules IGNORE_ALL = new IgnoreAllRules();
+
+	/**
+	 * Provides the instance of {@link IgnoreNothingRules}.
+	 */
+	public static final Rules IGNORE_NOTHING = new IgnoreNothingRules();
+
+	/**
+	 * @param fileName
+	 *            the name of the file or directory.
+	 * @param fileIsDirectory
+	 *            should be true if the file is a directory.
+	 * @return true if the file or directory should be ignored.
+	 */
+	public abstract boolean toIgnore(String fileName, boolean fileIsDirectory);
+
+	/**
+	 * @param directoryName
+	 *            the sub directory for which you want an {@link Rules}
+	 *            instance.
+	 * @return an {@link Rules} instance, which can be used to check files in
+	 *         the specified sub directory.
+	 */
+	public abstract Rules getRulesForSubDirectory(String directoryName);
+
+	/**
+	 * This implementation ignores everything.
+	 */
+	public static final class IgnoreAllRules implements Rules {
+		private IgnoreAllRules() {
+			// declared to make the constructor private
+		}
+
+		public Rules getRulesForSubDirectory(String directoryName) {
+			return this;
+		}
+
+		public boolean toIgnore(String fileName, boolean fileIsDirectory) {
+			return true;
+		}
+
+		@Override
+		public String toString() {
+			return "ignore all rules";
+		}
+	}
+
+	/**
+	 * This implementation ignores nothing.
+	 */
+	public static final class IgnoreNothingRules implements Rules {
+		private IgnoreNothingRules() {
+			// declared to make the constructor private
+		}
+
+		public Rules getRulesForSubDirectory(String directoryName) {
+			return this;
+		}
+
+		public boolean toIgnore(String fileName, boolean fileIsDirectory) {
+			return false;
+		}
+
+		@Override
+		public String toString() {
+			return "ignore nothing rules";
+		}
+	}
+
+}

@@ -0,0 +1,311 @@
+package org.spearce.jgit.lib;
+
+import org.spearce.jgit.errors.InvalidPatternException;
+
+import junit.framework.TestCase;
+
+public class FileNameMatcherTest extends TestCase {
+
+	private void assertMatch(final String pattern, final String input,
+			final boolean matchExpected,
+			final boolean extendResultInNoMatchExpected)
+			throws InvalidPatternException {
+		final FileNameMatcher matcher = new FileNameMatcher(pattern, null);
+		matcher.extendStringToMatch(input);
+		assertEquals(matchExpected, matcher.isMatch());
+		assertEquals(extendResultInNoMatchExpected, matcher
+				.willExtendResultInNoMatch());
+	}
+
+	private void assertFileNameMatch(final String pattern, final String input,
+			final char excludedCharacter, final boolean matchExpected,
+			final boolean extendResultInNoMatchExpected)
+			throws InvalidPatternException {
+		final FileNameMatcher matcher = new FileNameMatcher(pattern,
+				new Character(excludedCharacter));
+		matcher.extendStringToMatch(input);
+		assertEquals(matchExpected, matcher.isMatch());
+		assertEquals(extendResultInNoMatchExpected, matcher
+				.willExtendResultInNoMatch());
+	}
+
+	public void testVerySimplePatternCase0() throws Exception {
+		assertMatch("", "", true, true);
+	}
+
+	public void testVerySimplePatternCase1() throws Exception {
+		assertMatch("ab", "a", false, false);
+	}
+
+	public void testVerySimplePatternCase2() throws Exception {
+		assertMatch("ab", "ab", true, true);
+	}
+
+	public void testVerySimplePatternCase3() throws Exception {
+		assertMatch("ab", "ac", false, true);
+	}
+
+	public void testVerySimplePatternCase4() throws Exception {
+		assertMatch("ab", "abc", false, true);
+	}
+
+	public void testVerySimpleWirdcardCase0() throws Exception {
+		assertMatch("?", "a", true, true);
+	}
+
+	public void testVerySimpleWildCardCase1() throws Exception {
+		assertMatch("??", "a", false, false);
+	}
+
+	public void testVerySimpleWildCardCase2() throws Exception {
+		assertMatch("??", "ab", true, true);
+	}
+
+	public void testVerySimpleWildCardCase3() throws Exception {
+		assertMatch("??", "abc", false, true);
+	}
+
+	public void testVerySimpleStarCase0() throws Exception {
+		assertMatch("*", "", true, false);
+	}
+
+	public void testVerySimpleStarCase1() throws Exception {
+		assertMatch("*", "a", true, false);
+	}
+
+	public void testVerySimpleStarCase2() throws Exception {
+		assertMatch("*", "ab", true, false);
+	}
+
+	public void testSimpleStarCase0() throws Exception {
+		assertMatch("a*b", "a", false, false);
+	}
+
+	public void testSimpleStarCase1() throws Exception {
+		assertMatch("a*c", "ac", true, false);
+	}
+
+	public void testSimpleStarCase2() throws Exception {
+		assertMatch("a*c", "ab", false, false);
+	}
+
+	public void testSimpleStarCase3() throws Exception {
+		assertMatch("a*c", "abc", true, false);
+	}
+
+	public void testManySolutionsCase0() throws Exception {
+		assertMatch("a*a*a", "aaa", true, false);
+	}
+
+	public void testManySolutionsCase1() throws Exception {
+		assertMatch("a*a*a", "aaaa", true, false);
+	}
+
+	public void testManySolutionsCase2() throws Exception {
+		assertMatch("a*a*a", "ababa", true, false);
+	}
+
+	public void testManySolutionsCase3() throws Exception {
+		assertMatch("a*a*a", "aaaaaaaa", true, false);
+	}
+
+	public void testManySolutionsCase4() throws Exception {
+		assertMatch("a*a*a", "aaaaaaab", false, false);
+	}
+
+	public void testVerySimpleGroupCase0() throws Exception {
+		assertMatch("[ab]", "a", true, true);
+	}
+
+	public void testVerySimpleGroupCase1() throws Exception {
+		assertMatch("[ab]", "b", true, true);
+	}
+
+	public void testVerySimpleGroupCase2() throws Exception {
+		assertMatch("[ab]", "ab", false, true);
+	}
+
+	public void testVerySimpleGroupRangeCase0() throws Exception {
+		assertMatch("[b-d]", "a", false, true);
+	}
+
+	public void testVerySimpleGroupRangeCase1() throws Exception {
+		assertMatch("[b-d]", "b", true, true);
+	}
+
+	public void testVerySimpleGroupRangeCase2() throws Exception {
+		assertMatch("[b-d]", "c", true, true);
+	}
+
+	public void testVerySimpleGroupRangeCase3() throws Exception {
+		assertMatch("[b-d]", "d", true, true);
+	}
+
+	public void testVerySimpleGroupRangeCase4() throws Exception {
+		assertMatch("[b-d]", "e", false, true);
+	}
+
+	public void testVerySimpleGroupRangeCase5() throws Exception {
+		assertMatch("[b-d]", "-", false, true);
+	}
+
+	public void testTwoGroupsCase0() throws Exception {
+		assertMatch("[b-d][ab]", "bb", true, true);
+	}
+
+	public void testTwoGroupsCase1() throws Exception {
+		assertMatch("[b-d][ab]", "ca", true, true);
+	}
+
+	public void testTwoGroupsCase2() throws Exception {
+		assertMatch("[b-d][ab]", "fa", false, true);
+	}
+
+	public void testTwoGroupsCase3() throws Exception {
+		assertMatch("[b-d][ab]", "bc", false, true);
+	}
+
+	public void testTwoRangesInOneGroupCase0() throws Exception {
+		assertMatch("[b-ce-e]", "a", false, true);
+	}
+
+	public void testTwoRangesInOneGroupCase1() throws Exception {
+		assertMatch("[b-ce-e]", "b", true, true);
+	}
+
+	public void testTwoRangesInOneGroupCase2() throws Exception {
+		assertMatch("[b-ce-e]", "c", true, true);
+	}
+
+	public void testTwoRangesInOneGroupCase3() throws Exception {
+		assertMatch("[b-ce-e]", "d", false, true);
+	}
+
+	public void testTwoRangesInOneGroupCase4() throws Exception {
+		assertMatch("[b-ce-e]", "e", true, true);
+	}
+
+	public void testTwoRangesInOneGroupCase5() throws Exception {
+		assertMatch("[b-ce-e]", "f", false, true);
+	}
+
+	public void testIncompleteRangesInOneGroupCase0() throws Exception {
+		assertMatch("a[b-]", "ab", true, true);
+	}
+
+	public void testIncompleteRangesInOneGroupCase1() throws Exception {
+		assertMatch("a[b-]", "ac", false, true);
+	}
+
+	public void testIncompleteRangesInOneGroupCase2() throws Exception {
+		assertMatch("a[b-]", "a-", true, true);
+	}
+
+	public void testCombinedRangesInOneGroupCase0() throws Exception {
+		assertMatch("[a-c-e]", "b", true, true);
+	}
+
+	/**
+	 * The c belongs to the range a-c. "-e" is no valid range so d should not
+	 * match.
+	 * 
+	 * @throws Exception
+	 *             for some reasons
+	 */
+	public void testCombinedRangesInOneGroupCase1() throws Exception {
+		assertMatch("[a-c-e]", "d", false, true);
+	}
+
+	public void testCombinedRangesInOneGroupCase2() throws Exception {
+		assertMatch("[a-c-e]", "e", true, true);
+	}
+
+	public void testInversedGroupCase0() throws Exception {
+		assertMatch("[!b-c]", "a", true, true);
+	}
+
+	public void testInversedGroupCase1() throws Exception {
+		assertMatch("[!b-c]", "b", false, true);
+	}
+
+	public void testInversedGroupCase2() throws Exception {
+		assertMatch("[!b-c]", "c", false, true);
+	}
+
+	public void testInversedGroupCase3() throws Exception {
+		assertMatch("[!b-c]", "d", true, true);
+	}
+
+	public void testFilePathSimpleCase() throws Exception {
+		assertFileNameMatch("a/b", "a/b", '/', true, true);
+	}
+
+	public void testFilePathCase0() throws Exception {
+		assertFileNameMatch("a*b", "a/b", '/', false, true);
+	}
+
+	public void testFilePathCase1() throws Exception {
+		assertFileNameMatch("a?b", "a/b", '/', false, true);
+	}
+
+	public void testFilePathCase2() throws Exception {
+		assertFileNameMatch("a*b", "a\\b", '\\', false, true);
+	}
+
+	public void testFilePathCase3() throws Exception {
+		assertFileNameMatch("a?b", "a\\b", '\\', false, true);
+	}
+
+	public void testReset() throws Exception {
+		final String pattern = "helloworld";
+		final FileNameMatcher matcher = new FileNameMatcher(pattern, null);
+		matcher.extendStringToMatch("helloworld");
+		assertEquals(true, matcher.isMatch());
+		assertEquals(true, matcher.willExtendResultInNoMatch());
+		matcher.resetStringToMatch();
+		matcher.extendStringToMatch("hello");
+		assertEquals(false, matcher.isMatch());
+		assertEquals(false, matcher.willExtendResultInNoMatch());
+		matcher.extendStringToMatch("world");
+		assertEquals(true, matcher.isMatch());
+		assertEquals(true, matcher.willExtendResultInNoMatch());
+		matcher.extendStringToMatch("to much");
+		assertEquals(false, matcher.isMatch());
+		assertEquals(true, matcher.willExtendResultInNoMatch());
+		matcher.resetStringToMatch();
+		matcher.extendStringToMatch("helloworld");
+		assertEquals(true, matcher.isMatch());
+		assertEquals(true, matcher.willExtendResultInNoMatch());
+	}
+
+	public void testCreateMatcherForSuffix() throws Exception {
+		final String pattern = "helloworld";
+		final FileNameMatcher matcher = new FileNameMatcher(pattern, null);
+		matcher.extendStringToMatch("hello");
+		final FileNameMatcher childMatcher = matcher.createMatcherForSuffix();
+		assertEquals(false, matcher.isMatch());
+		assertEquals(false, matcher.willExtendResultInNoMatch());
+		assertEquals(false, childMatcher.isMatch());
+		assertEquals(false, childMatcher.willExtendResultInNoMatch());
+		matcher.extendStringToMatch("world");
+		assertEquals(true, matcher.isMatch());
+		assertEquals(true, matcher.willExtendResultInNoMatch());
+		assertEquals(false, childMatcher.isMatch());
+		assertEquals(false, childMatcher.willExtendResultInNoMatch());
+		childMatcher.extendStringToMatch("world");
+		assertEquals(true, matcher.isMatch());
+		assertEquals(true, matcher.willExtendResultInNoMatch());
+		assertEquals(true, childMatcher.isMatch());
+		assertEquals(true, childMatcher.willExtendResultInNoMatch());
+		childMatcher.resetStringToMatch();
+		assertEquals(true, matcher.isMatch());
+		assertEquals(true, matcher.willExtendResultInNoMatch());
+		assertEquals(false, childMatcher.isMatch());
+		assertEquals(false, childMatcher.willExtendResultInNoMatch());
+		childMatcher.extendStringToMatch("world");
+		assertEquals(true, matcher.isMatch());
+		assertEquals(true, matcher.willExtendResultInNoMatch());
+		assertEquals(true, childMatcher.isMatch());
+		assertEquals(true, childMatcher.willExtendResultInNoMatch());
+	}
+}

@@ -0,0 +1,376 @@
+package org.spearce.jgit.lib;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.spearce.jgit.errors.InvalidPatternException;
+
+/**
+ * This class can be used to match filenames against fnmatch like patterns. It
+ * is not thread save.
+ */
+public class FileNameMatcher {
+	private static final List<Head> EMPTY_HEAD_LIST = Collections.emptyList();
+
+	private List<Head> headsStartValue;
+
+	private List<Head> heads;
+
+	/**
+	 * {{@link #extendStringToMatchByOneCharacter(char)} needs a list for the
+	 * new heads, allocating a new array would be bad for the performance, as
+	 * the method gets called very often.
+	 * 
+	 */
+	private List<Head> listForLocalUseage;
+
+	/**
+	 * 
+	 * @param headsStartValue
+	 *            must be a list which will never be modified.
+	 */
+	private FileNameMatcher(final List<Head> headsStartValue) {
+		this.headsStartValue = headsStartValue;
+		this.heads = new ArrayList<Head>(headsStartValue.size());
+		this.heads.addAll(this.headsStartValue);
+		this.listForLocalUseage = new ArrayList<Head>(headsStartValue.size());
+	}
+
+	/**
+	 * @param patternString
+	 *            must contain a pattern which fnmatch would accept.
+	 * @param invalidWildgetCharacter
+	 *            if this parameter isn't null then this character will not
+	 *            match at wildcards(* and ? are wildcards).
+	 * @throws InvalidPatternException
+	 *             if the patternString contains a invalid fnmatch pattern.
+	 */
+	public FileNameMatcher(final String patternString,
+			final Character invalidWildgetCharacter)
+			throws InvalidPatternException {
+		this(createHeadsStartValues(patternString, invalidWildgetCharacter));
+	}
+
+	private static List<Head> createHeadsStartValues(
+			final String patternString, final Character invalidWildgetCharacter)
+			throws InvalidPatternException {
+		List<Head> nextHeadsSuggestion = new ArrayList<Head>(2);
+		nextHeadsSuggestion.add(LastHead.INSTANCE);
+
+		final char previosChracter = '\n';
+		int i = patternString.length() - 1;
+		while (i >= 0) {
+			final char c = patternString.charAt(i);
+
+			switch (c) {
+			case '*': {
+				if (previosChracter != '*') {
+					final AbstractHead head = createWildCardHead(invalidWildgetCharacter);
+					nextHeadsSuggestion.add(head);
+					head.setNewHeads(nextHeadsSuggestion);
+				}
+				break;
+			}
+			case '?': {
+				final AbstractHead head = createWildCardHead(invalidWildgetCharacter);
+				head.setNewHeads(nextHeadsSuggestion);
+				nextHeadsSuggestion = new ArrayList<Head>(2);
+				nextHeadsSuggestion.add(head);
+				break;
+			}
+			case ']': {
+				final String groupPattern = extractGroupPatternWithoutBrackets(
+						patternString, i);
+				i -= groupPattern.length() + 1;
+				final AbstractHead head = new GroupHead(groupPattern);
+				head.setNewHeads(nextHeadsSuggestion);
+				nextHeadsSuggestion = new ArrayList<Head>(2);
+				nextHeadsSuggestion.add(head);
+				break;
+			}
+			case '[': {
+				final String message = String
+						.format("There is no closing ] for the character [ at "
+								+ i);
+				throw new InvalidPatternException(message, patternString);
+			}
+			default: {
+				final CharacterHead head = new CharacterHead(c);
+				head.setNewHeads(nextHeadsSuggestion);
+				nextHeadsSuggestion = new ArrayList<Head>(2);
+				nextHeadsSuggestion.add(head);
+			}
+			}
+			i--;
+
+		}
+		return nextHeadsSuggestion;
+	}
+
+	private static String extractGroupPatternWithoutBrackets(
+			final String patternString, int closingBracketIndex)
+			throws InvalidPatternException {
+		int start = closingBracketIndex - 1;
+		while (start >= 0) {
+			final char possibleStartCharacter = patternString.charAt(start);
+			if (possibleStartCharacter == '[') {
+				break;
+			}
+			if (possibleStartCharacter == ']') {
+				final String message = String
+						.format(
+								"Found two ] characters at %s and %s without a [ character between.",
+								String.valueOf(start), String
+										.valueOf(closingBracketIndex));
+				throw new InvalidPatternException(message, patternString);
+			}
+			start--;
+		}
+		if (start < 0) {
+			final String message = String
+					.format(
+							"Found a ] character at %s but no [ character infront of it.",
+							String.valueOf(closingBracketIndex));
+			throw new InvalidPatternException(message, patternString);
+		}
+		final String groupPatternWithOutBrackets = patternString.substring(
+				start + 1, closingBracketIndex);
+		return groupPatternWithOutBrackets;
+	}
+
+	private static AbstractHead createWildCardHead(
+			final Character invalidWildgetCharacter) {
+		if (invalidWildgetCharacter != null)
+			return new RestrictedWildCardHead(invalidWildgetCharacter
+					.charValue());
+		else
+			return new WildCardHead();
+	}
+
+	private void extendStringToMatchByOneCharacter(final char c) {
+		final List<Head> newHeads = listForLocalUseage;
+		newHeads.clear();
+		List<Head> lastAddedHeads = null;
+		for (int i = 0; i < heads.size(); i++) {
+			final Head head = heads.get(i);
+			final List<Head> headsToAdd = head.getNextHeads(c);
+			// Why the next performance optimization isn't wrong:
+			// Some times two heads return the very same list.
+			// We save future effort if we don't add these heads again.
+			// This is the case with the heads "a" and "*" of "a*b" which
+			// both can return the list ["*","b"]
+			if (headsToAdd != lastAddedHeads) {
+				newHeads.addAll(headsToAdd);
+				lastAddedHeads = headsToAdd;
+			}
+		}
+		listForLocalUseage = heads;
+		heads = newHeads;
+	}
+
+	/**
+	 * 
+	 * @param stringToMatch
+	 *            extends the string which is matched against the patterns of
+	 *            this class.
+	 */
+	public void extendStringToMatch(final String stringToMatch) {
+		for (int i = 0; i < stringToMatch.length(); i++) {
+			final char c = stringToMatch.charAt(i);
+			extendStringToMatchByOneCharacter(c);
+		}
+	}
+
+	/**
+	 * Resets this matcher to it's state right after construction.
+	 */
+	public void resetStringToMatch() {
+		heads.clear();
+		heads.addAll(headsStartValue);
+	}
+
+	/**
+	 * 
+	 * @return a {@link FileNameMatcher} instance which uses the same pattern
+	 *         like this matcher, but has the current state of this matcher as
+	 *         reset and start point.
+	 */
+	public FileNameMatcher createMatcherForSuffix() {
+		final List<Head> copyOfHeads = new ArrayList<Head>(heads.size());
+		copyOfHeads.addAll(heads);
+		return new FileNameMatcher(copyOfHeads);
+	}
+
+	private interface Head {
+		/**
+		 * 
+		 * @param c
+		 *            the character which decides which heads are returned.
+		 * @return a list of heads based on the input.
+		 */
+		public abstract List<Head> getNextHeads(char c);
+	}
+
+	private static abstract class AbstractHead implements Head {
+		private List<Head> newHeads = null;
+
+		protected abstract boolean matches(char c);
+
+		/**
+		 * 
+		 * @param newHeads
+		 *            a list of {@link Head}s which will not be modified.
+		 */
+		public final void setNewHeads(List<Head> newHeads) {
+			if (this.newHeads != null)
+				throw new IllegalStateException("Property is already non null");
+			this.newHeads = newHeads;
+		}
+
+		public List<Head> getNextHeads(char c) {
+			if (matches(c))
+				return newHeads;
+			else
+				return EMPTY_HEAD_LIST;
+		}
+	}
+
+	private static final class LastHead implements Head {
+		static final Head INSTANCE = new LastHead();
+
+		/**
+		 * Don't call this constructor, use {@link #INSTANCE}
+		 */
+		private LastHead() {
+			// defined because of javadoc and visibility modifier.
+		}
+
+		public List<Head> getNextHeads(char c) {
+			return EMPTY_HEAD_LIST;
+		}
+
+	}
+
+	private static final class CharacterHead extends AbstractHead {
+		private final char expectedCharacter;
+
+		protected CharacterHead(final char expectedCharacter) {
+			this.expectedCharacter = expectedCharacter;
+		}
+
+		@Override
+		protected final boolean matches(final char c) {
+			return c == expectedCharacter;
+		}
+
+	}
+
+	private static final class WildCardHead extends AbstractHead {
+		@Override
+		protected final boolean matches(final char c) {
+			return true;
+		}
+	}
+
+	private static final class RestrictedWildCardHead extends AbstractHead {
+		private final char excludedCharacter;
+
+		RestrictedWildCardHead(final char excludedCharacter) {
+			this.excludedCharacter = excludedCharacter;
+		}
+
+		@Override
+		protected final boolean matches(final char c) {
+			return c != excludedCharacter;
+		}
+	}
+
+	private static final class GroupHead extends AbstractHead {
+		private final List<CharacterRange> ranges;
+
+		private final boolean inverse;
+
+		GroupHead(String pattern) {
+			this.ranges = new ArrayList<CharacterRange>();
+			this.inverse = pattern.startsWith("!");
+			if (inverse) {
+				pattern = pattern.substring(1);
+			}
+			final Pattern regexPattern = Pattern.compile("[^-][-][^-]");
+			final Matcher matcher = regexPattern.matcher(pattern);
+			while (matcher.find()) {
+				final String rangeString = matcher.group(0);
+				final char start = rangeString.charAt(0);
+				final char end = rangeString.charAt(2);
+				ranges.add(new CharacterRange(start, end));
+				pattern = matcher.replaceFirst("");
+				matcher.reset(pattern);
+			}
+			// pattern contains now no ranges
+			for (int i = 0; i < pattern.length(); i++) {
+				final char c = pattern.charAt(i);
+				ranges.add(new CharacterRange(c, c));
+			}
+		}
+
+		@Override
+		protected final boolean matches(final char c) {
+			for (CharacterRange range : ranges) {
+				if (range.inRange(c)) {
+					return !inverse;
+				}
+			}
+			return inverse;
+		}
+
+		private static final class CharacterRange {
+			private final char start;
+
+			private final char end;
+
+			CharacterRange(char start, char end) {
+				this.start = start;
+				this.end = end;
+			}
+
+			boolean inRange(char c) {
+				return start <= c && c <= end;
+			}
+
+		}
+	}
+
+	/**
+	 * 
+	 * @return true, if the string currently beeing matched does match.
+	 */
+	public boolean isMatch() {
+		final ListIterator<Head> headIterator = heads
+				.listIterator(heads.size());
+		while (headIterator.hasPrevious()) {
+			final Head head = headIterator.previous();
+			if (head == LastHead.INSTANCE) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+	/**
+	 * 
+	 * @return true, if the string beeing matched will not match when the string
+	 *         gets extended.
+	 */
+	public boolean willExtendResultInNoMatch() {
+		for (int i = 0; i < heads.size(); i++) {
+			if (heads.get(i) != LastHead.INSTANCE) {
+				return false;
+			}
+		}
+		return true;
+	}
+}