Implement a tree diff, that allows to compare directory trees

[matthiasblaesing]

Usage: Select exactly two folder entries in the project/files/favorites, open the context menu and select "Tools" -> "Tree diff"

This results in a flattened view of the difference between the two trees:

• Entries with red background are present in the source, but not in the target
• Entries with blue background are present in both locations but differ
• Entries with green background are present in the target, but not in the source

The list of modified files/folder can be display as hierarchy:

When a modified file is selected the diff view shows both versions and allows to update the target:

Additionally actions can be invoked directly on the difference entries:

Closes: #8349

[matthiasblaesing]

As this has little side effects and would be trivial to remove, I intent to merge at the end of week, unless someone objects.

[ebarboni]

LGTM

[neilcsmith-net]

For info, this addition seems to be causing an exception to be thrown in a platform application. I need to look more to see if it can be triggered in the IDE. The application is calling Mode::getTopComponents which then ends up throwing -

Class: class org.netbeans.modules.diff.tree.TreeDiffViewerTopComponent
Source: MultiFileObject@9a12497[Windows2Local/Components/TreeDiffViewerTopComponent.settings]
Caused: java.lang.NoSuchMethodException: org.netbeans.modules.diff.tree.TreeDiffViewerTopComponent.<init>()

[matthiasblaesing]

@neilcsmith-net do you have a full stack trace?

[neilcsmith-net]

@matthiasblaesing this should cover it from the mode impl up -

INFO [org.netbeans.core.windows.persistence]: [PersistenceManager.getTopComponentForID] Problem when deserializing TopComponent for tcID:'TreeDiffViewerTopComponent'. Reason: null
Content: 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE settings PUBLIC "-//NetBeans//DTD Session settings 1.0//EN" "http://www.netbeans.org/dtds/sessionsettings-1_0.dtd">
<settings version="1.0">
  <instance class="org.netbeans.modules.diff.tree.TreeDiffViewerTopComponent"/>
</settings>
Class: class org.netbeans.modules.diff.tree.TreeDiffViewerTopComponent
Source: MultiFileObject@6c5efbe8[Windows2Local/Components/TreeDiffViewerTopComponent.settings]
Content: 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE settings PUBLIC "-//NetBeans//DTD Session settings 1.0//EN" "http://www.netbeans.org/dtds/sessionsettings-1_0.dtd">
<settings version="1.0">
  <instance class="org.netbeans.modules.diff.tree.TreeDiffViewerTopComponent"/>
</settings>
Class: class org.netbeans.modules.diff.tree.TreeDiffViewerTopComponent
Source: MultiFileObject@6c5efbe8[Windows2Local/Components/TreeDiffViewerTopComponent.settings]
Caused: java.lang.NoSuchMethodException: org.netbeans.modules.diff.tree.TreeDiffViewerTopComponent.<init>()
	at java.base/java.lang.Class.getConstructor0(Class.java:3218)
	at java.base/java.lang.Class.getDeclaredConstructor(Class.java:2493)
	at org.netbeans.modules.settings.convertors.XMLSettingsSupport.newInstance(XMLSettingsSupport.java:73)
	at org.netbeans.modules.settings.convertors.XMLSettingsSupport$SettingsRecognizer.instanceCreate(XMLSettingsSupport.java:610)
Caused: java.io.IOException
	at org.netbeans.modules.settings.convertors.XMLSettingsSupport$SettingsRecognizer.instanceCreate(XMLSettingsSupport.java:612)
	at org.netbeans.modules.settings.convertors.SerialDataConvertor$SettingsInstance.instanceCreate(SerialDataConvertor.java:399)
[catch] at org.netbeans.core.windows.persistence.PersistenceManager.getTopComponentPersistentForID(PersistenceManager.java:547)
	at org.netbeans.core.windows.persistence.PersistenceManager.getTopComponentForID(PersistenceManager.java:657)
	at org.netbeans.core.windows.PersistenceHandler.getTopComponentForID(PersistenceHandler.java:453)
	at org.netbeans.core.windows.WindowManagerImpl.getTopComponentForID(WindowManagerImpl.java:995)
	at org.netbeans.core.windows.model.TopComponentSubModel.getTopComponent(TopComponentSubModel.java:353)
	at org.netbeans.core.windows.model.TopComponentSubModel.getTopComponents(TopComponentSubModel.java:65)
	at org.netbeans.core.windows.model.DefaultModeModel.getTopComponents(DefaultModeModel.java:415)
	at org.netbeans.core.windows.model.DefaultModel.getModeTopComponents(DefaultModel.java:907)
	at org.netbeans.core.windows.Central.getModeTopComponents(Central.java:1541)
	at org.netbeans.core.windows.ModeImpl.getTopComponents(ModeImpl.java:200)

I'm going to replace the call with something else in the application, but I'm not sure if anything else in the IDE or elsewhere may hit part of this stack.