#
#
# patch "res/forms/preferences.ui"
#  from [c9f2e477b8119f70eda6fcc2f8bcfb3fae7f53a9]
#    to [a9a465be6c538be9e4fbba44725483c44243f4c5]
# 
# patch "src/model/ContentDiff.cpp"
#  from [fba40b0f3894f67596c8ea99293ab78212535b53]
#    to [d5f9c1f13e38f6aee86944e9a30cc70ed4aa07dd]
# 
# patch "src/monotone/MonotoneUtil.cpp"
#  from [c18789f0f92cceb714cca6b981e50ab2437ea9ff]
#    to [1e21ab79a5d485224d25e9764623c5011840cc8e]
# 
# patch "src/monotone/MonotoneUtil.h"
#  from [2859545454f0987d0bb5141a06a1f34667a9dc51]
#    to [13e7aebbd695979af145534728db918ab6effa2c]
# 
# patch "src/view/dialogs/Preferences.cpp"
#  from [211cc5978c8f41c19d41165fe4e56951043989cf]
#    to [965a695baebe0fe9f6c4330e90b657cacc772145]
#
============================================================
--- res/forms/preferences.ui	c9f2e477b8119f70eda6fcc2f8bcfb3fae7f53a9
+++ res/forms/preferences.ui	a9a465be6c538be9e4fbba44725483c44243f4c5
@@ -294,6 +294,19 @@
         </widget>
        </item>
        <item>
+        <widget class="QCheckBox" name="fixUnwantedReverseDiffs" >
+         <property name="toolTip" >
+          <string>This option effectively disables the generation of reverse diffs.</string>
+         </property>
+         <property name="text" >
+          <string>fix parent-child selection for diff views</string>
+         </property>
+         <property name="checked" >
+          <bool>true</bool>
+         </property>
+        </widget>
+       </item>
+       <item>
         <widget class="QCheckBox" name="saveEncodingAsFileAttribute" >
          <property name="text" >
           <string>save encoding preference as file attribute</string>
============================================================
--- src/model/ContentDiff.cpp	fba40b0f3894f67596c8ea99293ab78212535b53
+++ src/model/ContentDiff.cpp	d5f9c1f13e38f6aee86944e9a30cc70ed4aa07dd
@@ -53,8 +53,21 @@ void ContentDiff::readDatabaseDiff(const
         cmd << fileName;
     }
 
+    QStringList revs;
+    revs << base << target;
+    // sort base and target topologically in case the user accidently chosed
+    // the child as base and the parent as target (and would therefor get a
+    // reverse diff)
+    if (Settings::getBool("FixUnwantedReverseDiffs", true))
+    {
+        revs = MonotoneUtil::topsortRevisions(db, revs);
+    }
+
     QStringList opts;
-    opts << "r" << base << "r" << target;
+    foreach (QString r, revs)
+    {
+        opts << "r" << r;
+    }
 
     MonotoneTask task(cmd, opts);
 
@@ -78,17 +91,30 @@ void ContentDiff::readWorkspaceDiff(cons
         cmd << fileName;
     }
 
-    QStringList opts;
+    QStringList revs;
     if (!base.isEmpty())
     {
-        opts << "r" << base;
+        revs << base;
     }
+    if (!target.isEmpty())
+    {
+        revs << target;
+    }
 
-    if (!target.isEmpty())
+    // sort base and target topologically in case the user accidently chosed
+    // the child as base and the parent as target (and would therefor get a
+    // reverse diff)
+    if (revs.size() == 2 && Settings::getBool("FixUnwantedReverseDiffs", true))
     {
-        opts << "r" << target;
+        revs = MonotoneUtil::topsortRevisions(MonotoneUtil::getDatabaseFile(ws), revs);
     }
 
+    QStringList opts;
+    foreach (QString r, revs)
+    {
+        opts << "r" << r;
+    }
+
     MonotoneTask task(cmd, opts);
 
     if (!encoding.isEmpty())
============================================================
--- src/monotone/MonotoneUtil.cpp	c18789f0f92cceb714cca6b981e50ab2437ea9ff
+++ src/monotone/MonotoneUtil.cpp	1e21ab79a5d485224d25e9764623c5011840cc8e
@@ -94,6 +94,7 @@ QString MonotoneUtil::getBaseWorkspaceRe
         return QString();
     }
 
+
     data.chop(1);
 
     // we cannot handle workspaces with multiple parents yet
@@ -349,6 +350,26 @@ QString MonotoneUtil::getFileId(const Da
     return data;
 }
 
+QStringList MonotoneUtil::topsortRevisions(const DatabaseFile & db, const QStringList & revs)
+{
+    QStringList args;
+    args << "toposort";
+    args += revs;
+    MonotoneTask in(args);
+    MonotoneTask out = runSynchronousDatabaseTask(db, in);
+    if (!out.isFinished()) F("task aborted");
+
+    QString data = out.getDecodedOutput();
+    if (out.getReturnCode() > 0)
+    {
+        C(QString("Couldn't toposort revisions: %1").arg(data));
+        // return the list unchanged
+        return revs;
+    }
+
+    return data.split("\n", QString::SkipEmptyParts);
+}
+
 bool MonotoneUtil::getAttribute(const WorkspacePath & ws, const QString & path,
                   const QString & attrname, QPair<QString, QString> & attrval)
 {
============================================================
--- src/monotone/MonotoneUtil.h	2859545454f0987d0bb5141a06a1f34667a9dc51
+++ src/monotone/MonotoneUtil.h	13e7aebbd695979af145534728db918ab6effa2c
@@ -40,6 +40,7 @@ public:
     static FileEntryList getRevisionManifest(const DatabaseFile &, const QString &);
     static QStringList getPrivateKeyList(const DatabaseFile &);
     static QString getFileId(const DatabaseFile &, const QString &);
+    static QStringList topsortRevisions(const DatabaseFile &, const QStringList &);
     static bool getAttribute(const WorkspacePath &, const QString &, const QString &, QPair<QString, QString> &);
     static bool getAttribute(const DatabaseFile &, const QString &, const QString &, const QString &, QString &);
 
============================================================
--- src/view/dialogs/Preferences.cpp	211cc5978c8f41c19d41165fe4e56951043989cf
+++ src/view/dialogs/Preferences.cpp	965a695baebe0fe9f6c4330e90b657cacc772145
@@ -100,6 +100,11 @@ void Preferences::init()
         Qt::Checked : Qt::Unchecked
     );
 
+    fixUnwantedReverseDiffs->setCheckState(
+        Settings::getBool("FixUnwantedReverseDiffs", true) ?
+        Qt::Checked : Qt::Unchecked
+    );
+
     saveEncodingAsFileAttribute->setCheckState(
         Settings::getBool("SaveEncodingAsFileAttribute", true) ?
         Qt::Checked : Qt::Unchecked
@@ -186,6 +191,7 @@ void Preferences::accept()
 
     Settings::setBool("CheckForUpdates", checkForUpdates->isChecked());
     Settings::setBool("SaveEncodingAsFileAttribute", saveEncodingAsFileAttribute->isChecked());
+    Settings::setBool("FixUnwantedReverseDiffs", fixUnwantedReverseDiffs->isChecked());
     Settings::setBool("RelaxedVersionCheck", relaxedVersionCheck->isChecked());
     Settings::setBool("AskFileOpen", askFileOpen->isChecked());
     Settings::setString("AskFileOpenExt", askFileOpenExtensions->text());