Trim indent/newlines in text-based package metadata

This allows having newlines in the csproj while still compacting for packing.

The trimming involves:
* Removing blank lines at the beginning and ending of the value
* Determining indenting on the first line and using that to remove subsequent indenting in all following lines.
* Applying markdown rules to remove newlines: meaning only full paragraph separating newlines (blank) will be kept.
* Collapse multiple blank newlines into just one (when separating paragraphs).

This means you can indent nicely in the XML (as VS does by default) while still keeping a clean and compact representation in the package. For example:

```xml
    <Description>
      Create, edit and run multiple C# top-level programs in the same project,
      respecting per-file `#:package` references and `#:property` 😍
    </Description>
```
Would become a single line of text.

Author: kzu

src/NuGetizer.Tasks/CreatePackage.cs

@@ -92,13 +92,13 @@ public Manifest CreateManifest()
                 metadata.DevelopmentDependency = true;
 
             if (Manifest.TryGetMetadata("Title", out var title))
-                metadata.Title = title;
+                metadata.Title = title.TrimIndent();
 
             if (Manifest.TryGetMetadata("Description", out var description))
-                metadata.Description = description;
+                metadata.Description = description.TrimIndent();
 
             if (Manifest.TryGetMetadata("Summary", out var summary))
-                metadata.Summary = summary;
+                metadata.Summary = summary.TrimIndent();
 
             if (Manifest.TryGetMetadata("Readme", out var readme))
                 metadata.Readme = readme;
@@ -171,7 +171,7 @@ public Manifest CreateManifest()
                 metadata.Icon = icon;
 
             if (Manifest.TryGetMetadata("ReleaseNotes", out var releaseNotes))
-                metadata.ReleaseNotes = releaseNotes;
+                metadata.ReleaseNotes = releaseNotes.TrimIndent();
 
             if (Manifest.TryGetMetadata("Tags", out var tags))
                 metadata.Tags = tags;

src/NuGetizer.Tasks/Extensions.cs

@@ -131,6 +131,83 @@ public static Manifest GetManifest(this IPackageCoreReader packageReader)
                 return null;
         }
 
+        public static string TrimIndent(this string value)
+        {
+            if (string.IsNullOrWhiteSpace(value))
+                return "";
+
+            // Read lines without the newline characters
+            using var sr = new StringReader(value);
+            var lines = new List<string>();
+            string? line;
+            while ((line = sr.ReadLine()) != null)
+            {
+                lines.Add(line);
+            }
+
+            // Find the first non-empty line
+            var start = 0;
+            while (start < lines.Count && string.IsNullOrWhiteSpace(lines[start]))
+            {
+                start++;
+            }
+            if (start == lines.Count)
+                return "";
+
+            // Determine the indentation prefix from the first content line
+            var firstContent = lines[start];
+            var indentLen = 0;
+            while (indentLen < firstContent.Length && char.IsWhiteSpace(firstContent[indentLen]))
+            {
+                indentLen++;
+            }
+            var indentPrefix = firstContent.Substring(0, indentLen);
+
+            // Find the last non-empty line
+            var end = lines.Count - 1;
+            while (end >= start && string.IsNullOrWhiteSpace(lines[end]))
+            {
+                end--;
+            }
+
+            // Trim indentation from each line
+            var trimmedLines = new List<string>();
+            for (var i = start; i <= end; i++)
+            {
+                var ln = lines[i];
+                var trimmed = ln.StartsWith(indentPrefix) ? ln.Substring(indentPrefix.Length) : ln;
+                trimmedLines.Add(trimmed);
+            }
+
+            // Collapse like Markdown: join lines within paragraphs with space, paragraphs separated by double newline
+            var paragraphs = new List<string>();
+            var currentPara = new List<string>();
+            for (var i = 0; i < trimmedLines.Count; i++)
+            {
+                var ln = trimmedLines[i];
+                if (string.IsNullOrWhiteSpace(ln))
+                {
+                    if (currentPara.Count > 0)
+                    {
+                        paragraphs.Add(string.Join(" ", currentPara.Select(l => l.TrimEnd())));
+                        currentPara.Clear();
+                    }
+                    // Skip blanks, multiple blanks collapse to one break
+                }
+                else
+                {
+                    currentPara.Add(ln);
+                }
+            }
+            if (currentPara.Count > 0)
+            {
+                paragraphs.Add(string.Join(" ", currentPara.Select(l => l.TrimEnd())));
+            }
+
+            // Join paragraphs with double newline
+            return string.Join(Environment.NewLine + Environment.NewLine, paragraphs);
+        }
+
         public static void LogErrorCode(this TaskLoggingHelper log, string code, string message, params object[] messageArgs) =>
             log.LogError(string.Empty, code, string.Empty, string.Empty, 0, 0, 0, 0, message, messageArgs);
 

src/NuGetizer.Tests/CreatePackageTests.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.IO.Compression;
@@ -35,7 +34,16 @@ public CreatePackageTests(ITestOutputHelper output)
                     { MetadataName.PackageId, "package" },
                     { MetadataName.Version, "1.0.0" },
                     { "Title", "title" },
-                    { "Description", "description" },
+                    { "Description",
+                        """
+
+                            This is the description.
+                            Indent will be trimmed.
+
+
+                            New paragraph preserved.
+
+                        """ },
                     { "Summary", "summary" },
                     { "Language", "en" },
 
@@ -111,7 +119,6 @@ public void when_creating_package_then_contains_all_metadata()
             Assert.Equal(task.Manifest.GetMetadata("PackageId"), metadata.Id);
             Assert.Equal(task.Manifest.GetMetadata("Version"), metadata.Version.ToString());
             Assert.Equal(task.Manifest.GetMetadata("Title"), metadata.Title);
-            Assert.Equal(task.Manifest.GetMetadata("Description"), metadata.Description);
             Assert.Equal(task.Manifest.GetMetadata("Summary"), metadata.Summary);
             Assert.Equal(task.Manifest.GetMetadata("Language"), metadata.Language);
             Assert.Equal(task.Manifest.GetMetadata("Copyright"), metadata.Copyright);
@@ -126,6 +133,15 @@ public void when_creating_package_then_contains_all_metadata()
                     Assert.Equal(PackageType.Dependency.Name, item.Name);
                     Assert.Equal(PackageType.EmptyVersion, item.Version);
                 });
+
+            // C#-style triming is applied.
+            Assert.Equal(
+                """
+                This is the description. Indent will be trimmed.
+
+                New paragraph preserved.
+                """,
+                metadata.Description);
         }
 
         [Fact]