Don't save solution-wide .sdsettings file if it is unchanged.

src/AddIns/BackendBindings/CSharpBinding/Project/Src/FormattingStrategy/CSharpFormattingOptionsPersistence.cs

@@ -118,7 +118,7 @@ namespace CSharpBinding.FormattingStrategy
 		{
 			// Load solution settings
 			SolutionOptions = new CSharpFormattingOptionsPersistence(
-				e.Solution.GlobalPreferences,
+				e.Solution.SDSettings,
 				new CSharpFormattingOptionsContainer(GlobalOptions.OptionsContainer)
 				{
 					DefaultText = StringParser.Parse("${res:CSharpBinding.Formatting.SolutionOptionReference}")

src/Main/Base/Project/Project/ISolution.cs

@@ -97,7 +97,7 @@ namespace ICSharpCode.SharpDevelop.Project
 		/// Gets a container that can be used to store data about the solution.
 		/// This data is stored along with .sln file as .sln.sdsettings.
 		/// </summary>
-		Properties GlobalPreferences { get; }
+		Properties SDSettings { get; }
 		
 		/// <summary>
 		/// This event is raised by <see cref="SavePreferences"/> immediately before the preferences are saved to disk.

src/Main/SharpDevelop/Project/Solution.cs

@@ -35,7 +35,7 @@ namespace ICSharpCode.SharpDevelop.Project
 	class Solution : SolutionFolder, ISolution
 	{
 		FileName fileName;
-		FileName globalSettingsFileName;
+		FileName sdSettingsFileName;
 		DirectoryName directory;
 		readonly IProjectChangeWatcher changeWatcher;
 		readonly IFileService fileService;
@@ -52,7 +52,7 @@ namespace ICSharpCode.SharpDevelop.Project
 			this.PlatformNames = new SolutionConfigurationOrPlatformNameCollection(this, true);
 			this.projects = new SynchronizedModelCollection<IProject>(new ProjectModelCollection(this));
 			this.FileName = fileName;
-			this.globalSettingsFileName = new FileName(fileName + ".sdsettings");
+			this.sdSettingsFileName = new FileName(fileName + ".sdsettings");
 			base.Name = fileName.GetFileNameWithoutExtension();
 			
 			this.globalSections = new SynchronizedModelCollection<SolutionSection>(new NullSafeSimpleModelCollection<SolutionSection>());
@@ -281,11 +281,11 @@ namespace ICSharpCode.SharpDevelop.Project
 			get { return preferences; }
 		}
 		
-		Properties globalPreferences = new Properties();
+		Properties sdSettings = new Properties();
 		
 		[Browsable(false)]
-		public Properties GlobalPreferences {
+		public Properties SDSettings {
-			get { return globalPreferences; }
+			get { return sdSettings; }
 		}
 		
 		string GetPreferencesKey()
@@ -297,7 +297,7 @@ namespace ICSharpCode.SharpDevelop.Project
 		{
 			try {
 				preferences = SD.PropertyService.LoadExtraProperties(GetPreferencesKey());
-				globalPreferences = Properties.Load(globalSettingsFileName);
+				sdSettings = Properties.Load(sdSettingsFileName);
 			} catch (IOException) {
 			} catch (XmlException) {
 				// ignore errors about inaccessible or malformed files
@@ -321,7 +321,9 @@ namespace ICSharpCode.SharpDevelop.Project
 			
 			try {
 				SD.PropertyService.SaveExtraProperties(GetPreferencesKey(), preferences);
-				globalPreferences.Save(globalSettingsFileName);
+				if (sdSettings.IsDirty) {
+					sdSettings.Save(sdSettingsFileName);
+				}
 			} catch (IOException) {
 				// ignore errors writing to extra properties
 			}