Make diff algorithm configurable
The diff algorithm which is used by Merge, Cherry-Pick, Rebase
should be configurable. A new configuration parameter "diff.algorithm"
is introduced which currently accepts the values "myers" or
"histogram". Based on this parameter for example the ResolveMerger
will choose a diff algorithm. The reason for this is bug 331078.
This bug shows that JGit is more compatible with C Git when
histogram diff is in place. But since histogram diff is quite new we
need an easy way to fall back to Myers diff.
Bug: 331078
Change-Id: I2549c992e478d991c61c9508ad826d1a9e539ae3
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Philipp Thun <philipp.thun@sap.com>
diff --git a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Diff.java b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Diff.java
index 6062f35..5060317 100644
--- a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Diff.java
+++ b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Diff.java
@@ -54,10 +54,9 @@
import java.util.List;
import org.eclipse.jgit.diff.DiffAlgorithm;
+import org.eclipse.jgit.diff.DiffAlgorithm.SupportedAlgorithm;
import org.eclipse.jgit.diff.DiffEntry;
import org.eclipse.jgit.diff.DiffFormatter;
-import org.eclipse.jgit.diff.HistogramDiff;
-import org.eclipse.jgit.diff.MyersDiff;
import org.eclipse.jgit.diff.RawTextComparator;
import org.eclipse.jgit.diff.RenameDetector;
import org.eclipse.jgit.dircache.DirCacheIterator;
@@ -101,19 +100,9 @@ void noRenames(@SuppressWarnings("unused") boolean on) {
detectRenames = Boolean.FALSE;
}
- enum SupportedAlgorithm {
- myers(MyersDiff.INSTANCE), histogram(new HistogramDiff());
-
- public DiffAlgorithm algorithm;
-
- SupportedAlgorithm(DiffAlgorithm a) {
- algorithm = a;
- }
- };
-
@Option(name = "--algorithm", metaVar = "metaVar_diffAlg", usage = "usage_diffAlgorithm")
void setAlgorithm(SupportedAlgorithm s) {
- diffFmt.setDiffAlgorithm(s.algorithm);
+ diffFmt.setDiffAlgorithm(DiffAlgorithm.getAlgorithm(s));
}
@Option(name = "-l", usage = "usage_renameLimit")
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/MergeAlgorithmTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/MergeAlgorithmTest.java
index 9b4b714..b17c527 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/MergeAlgorithmTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/MergeAlgorithmTest.java
@@ -166,7 +166,7 @@ public void testSeperateModifications() throws IOException {
}
private String merge(String commonBase, String ours, String theirs) throws IOException {
- MergeResult r = MergeAlgorithm.merge(RawTextComparator.DEFAULT,
+ MergeResult r = new MergeAlgorithm().merge(RawTextComparator.DEFAULT,
T(commonBase), T(ours), T(theirs));
ByteArrayOutputStream bo=new ByteArrayOutputStream(50);
fmt.formatMerge(bo, r, "B", "O", "T", Constants.CHARACTER_ENCODING);
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffAlgorithm.java b/org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffAlgorithm.java
index f6859a2..b20e325 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffAlgorithm.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffAlgorithm.java
@@ -54,6 +54,38 @@
*/
public abstract class DiffAlgorithm {
/**
+ * Supported diff algorithm
+ */
+ public enum SupportedAlgorithm {
+ /**
+ * Myers diff algorithm
+ */
+ MYERS,
+
+ /**
+ * Histogram diff algorithm
+ */
+ HISTOGRAM
+ }
+
+ /**
+ * @param alg
+ * the diff algorithm for which an implementation should be
+ * returned
+ * @return an implementation of the specified diff algorithm
+ */
+ public static DiffAlgorithm getAlgorithm(SupportedAlgorithm alg) {
+ switch (alg) {
+ case MYERS:
+ return MyersDiff.INSTANCE;
+ case HISTOGRAM:
+ return new HistogramDiff();
+ default:
+ throw new IllegalArgumentException();
+ }
+ }
+
+ /**
* Compare two sequences and identify a list of edits between them.
*
* @param <S>
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffFormatter.java b/org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffFormatter.java
index be9a86e..fa0cb9c 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffFormatter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffFormatter.java
@@ -63,6 +63,7 @@
import java.util.List;
import org.eclipse.jgit.JGitText;
+import org.eclipse.jgit.diff.DiffAlgorithm.SupportedAlgorithm;
import org.eclipse.jgit.diff.DiffEntry.ChangeType;
import org.eclipse.jgit.errors.AmbiguousObjectException;
import org.eclipse.jgit.errors.CorruptObjectException;
@@ -70,6 +71,7 @@
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.lib.AbbreviatedObjectId;
import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.ConfigConstants;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.FileMode;
import org.eclipse.jgit.lib.ObjectId;
@@ -118,7 +120,7 @@ public class DiffFormatter {
private int abbreviationLength = 7;
- private DiffAlgorithm diffAlgorithm = new HistogramDiff();
+ private DiffAlgorithm diffAlgorithm;
private RawTextComparator comparator = RawTextComparator.DEFAULT;
@@ -178,6 +180,12 @@ public void setRepository(Repository repository) {
setNewPrefix("");
}
setDetectRenames(dc.isRenameDetectionEnabled());
+
+ diffAlgorithm = DiffAlgorithm.getAlgorithm(db.getConfig().getEnum(
+ ConfigConstants.CONFIG_DIFF_SECTION, null,
+ ConfigConstants.CONFIG_KEY_ALGORITHM,
+ SupportedAlgorithm.HISTOGRAM));
+
}
/**
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java
index 4ca11d0..9f74206 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java
@@ -57,6 +57,12 @@ public class ConfigConstants {
/** The "remote" section */
public static final String CONFIG_REMOTE_SECTION = "remote";
+ /** The "diff" section */
+ public static final String CONFIG_DIFF_SECTION = "diff";
+
+ /** The "algorithm" key */
+ public static final String CONFIG_KEY_ALGORITHM = "algorithm";
+
/** The "autocrlf" key */
public static final String CONFIG_KEY_AUTOCRLF = "autocrlf";
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/merge/MergeAlgorithm.java b/org.eclipse.jgit/src/org/eclipse/jgit/merge/MergeAlgorithm.java
index aee0ba9..62febd6 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/merge/MergeAlgorithm.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/merge/MergeAlgorithm.java
@@ -47,6 +47,7 @@
import java.util.Iterator;
import java.util.List;
+import org.eclipse.jgit.diff.DiffAlgorithm;
import org.eclipse.jgit.diff.Edit;
import org.eclipse.jgit.diff.EditList;
import org.eclipse.jgit.diff.MyersDiff;
@@ -56,15 +57,27 @@
/**
* Provides the merge algorithm which does a three-way merge on content provided
- * as RawText. Makes use of {@link MyersDiff} to compute the diffs.
+ * as RawText. By default {@link MyersDiff} is used as diff algorithm.
*/
public final class MergeAlgorithm {
+ private final DiffAlgorithm diffAlg;
/**
- * Since this class provides only static methods I add a private default
- * constructor to prevent instantiation.
+ * Creates a new MergeAlgorithm which uses {@link MyersDiff} as diff
+ * algorithm
*/
- private MergeAlgorithm() {
+ public MergeAlgorithm() {
+ this(MyersDiff.INSTANCE);
+ }
+
+ /**
+ * Creates a new MergeAlgorithm
+ *
+ * @param diff
+ * the diff algorithm used by this merge
+ */
+ public MergeAlgorithm(DiffAlgorithm diff) {
+ this.diffAlg = diff;
}
// An special edit which acts as a sentinel value by marking the end the
@@ -83,16 +96,16 @@ private MergeAlgorithm() {
* @param theirs the second sequence to be merged
* @return the resulting content
*/
- public static <S extends Sequence> MergeResult<S> merge(
+ public <S extends Sequence> MergeResult<S> merge(
SequenceComparator<S> cmp, S base, S ours, S theirs) {
List<S> sequences = new ArrayList<S>(3);
sequences.add(base);
sequences.add(ours);
sequences.add(theirs);
- MergeResult result = new MergeResult<S>(sequences);
- EditList oursEdits = MyersDiff.INSTANCE.diff(cmp, base, ours);
+ MergeResult<S> result = new MergeResult<S>(sequences);
+ EditList oursEdits = diffAlg.diff(cmp, base, ours);
Iterator<Edit> baseToOurs = oursEdits.iterator();
- EditList theirsEdits = MyersDiff.INSTANCE.diff(cmp, base, theirs);
+ EditList theirsEdits = diffAlg.diff(cmp, base, theirs);
Iterator<Edit> baseToTheirs = theirsEdits.iterator();
int current = 0; // points to the next line (first line is 0) of base
// which was not handled yet
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/merge/ResolveMerger.java b/org.eclipse.jgit/src/org/eclipse/jgit/merge/ResolveMerger.java
index a6119ed..a1bda41 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/merge/ResolveMerger.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/merge/ResolveMerger.java
@@ -58,6 +58,8 @@
import java.util.Map;
import org.eclipse.jgit.JGitText;
+import org.eclipse.jgit.diff.DiffAlgorithm;
+import org.eclipse.jgit.diff.DiffAlgorithm.SupportedAlgorithm;
import org.eclipse.jgit.diff.RawText;
import org.eclipse.jgit.diff.RawTextComparator;
import org.eclipse.jgit.diff.Sequence;
@@ -71,6 +73,7 @@
import org.eclipse.jgit.errors.IndexWriteException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.errors.NoWorkTreeException;
+import org.eclipse.jgit.lib.ConfigConstants;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.FileMode;
import org.eclipse.jgit.lib.ObjectId;
@@ -136,6 +139,7 @@ public enum MergeFailureReason {
private WorkingTreeIterator workingTreeIterator;
+ private MergeAlgorithm mergeAlgorithm;
/**
* @param local
@@ -143,6 +147,11 @@ public enum MergeFailureReason {
*/
protected ResolveMerger(Repository local, boolean inCore) {
super(local);
+ SupportedAlgorithm diffAlg = local.getConfig().getEnum(
+ ConfigConstants.CONFIG_DIFF_SECTION, null,
+ ConfigConstants.CONFIG_KEY_ALGORITHM,
+ SupportedAlgorithm.HISTOGRAM);
+ mergeAlgorithm = new MergeAlgorithm(DiffAlgorithm.getAlgorithm(diffAlg));
commitNames = new String[] { "BASE", "OURS", "THEIRS" };
oi = getObjectInserter();
this.inCore = inCore;
@@ -459,7 +468,7 @@ private boolean contentMerge(CanonicalTreeParser base,
MergeFormatter fmt = new MergeFormatter();
// do the merge
- MergeResult<RawText> result = MergeAlgorithm.merge(
+ MergeResult<RawText> result = mergeAlgorithm.merge(
RawTextComparator.DEFAULT,
getRawText(base.getEntryObjectId(), db),
getRawText(ours.getEntryObjectId(), db),
