Revise the preprocessor symbols we use

src/NerdBank.GitVersioning/ManagedGit/GitPack.cs

@@ -39,7 +39,7 @@ public class GitPack : IDisposable
 
         // A histogram which tracks the objects which have been retrieved from this GitPack. The key is the offset
         // of the object. Used to get some insights in usage patterns.
-#if DEBUG && !NETSTANDARD
+#if DEBUG
         private readonly Dictionary<long, int> histogram = new Dictionary<long, int>();
 #endif
 
@@ -172,7 +172,7 @@ public bool TryGetObject(GitObjectId objectId, string objectType, out Stream? va
         /// </returns>
         public Stream GetObject(long offset, string objectType)
         {
-#if DEBUG && !NETSTANDARD
+#if DEBUG
             if (!this.histogram.TryAdd(offset, 1))
             {
                 this.histogram[offset] += 1;
@@ -230,7 +230,7 @@ public void GetCacheStatistics(StringBuilder builder)
         {
             builder.AppendLine($"Git Pack:");
 
-#if DEBUG && !NETSTANDARD
+#if DEBUG
             int histogramCount = 25;
             builder.AppendLine($"Top {histogramCount} / {this.histogram.Count} items:");
 

src/NerdBank.GitVersioning/ManagedGit/GitPackDeltafiedStream.cs

@@ -64,7 +64,7 @@ public override long Position
             set => throw new NotImplementedException();
         }
 
-#if NETSTANDARD
+#if NETSTANDARD2_0
         /// <summary>
         /// Reads a sequence of bytes from the current <see cref="GitPackDeltafiedStream"/> and advances the position
         /// within the stream by the number of bytes read.

src/NerdBank.GitVersioning/ManagedGit/GitPackMemoryCacheStream.cs

@@ -37,7 +37,7 @@ public override void Flush()
             throw new NotSupportedException();
         }
 
-#if NETSTANDARD
+#if NETSTANDARD2_0
         public int Read(Span<byte> buffer)
 #else
         /// <inheritdoc/>

src/NerdBank.GitVersioning/ManagedGit/GitPackMemoryCacheViewStream.cs

@@ -37,7 +37,7 @@ public override int Read(byte[] buffer, int offset, int count)
             return this.Read(buffer.AsSpan(offset, count));
         }
 
-#if NETSTANDARD
+#if NETSTANDARD2_0
         public int Read(Span<byte> buffer)
 #else
         /// <inheritdoc/>

src/NerdBank.GitVersioning/ManagedGit/GitPackPooledStream.cs

@@ -62,7 +62,7 @@ public override void Flush()
             this.stream.Flush();
         }
 
-#if !NETSTANDARD
+#if !NETSTANDARD2_0
         /// <inheritdoc/>
         public override int Read(Span<byte> buffer)
         {

src/NerdBank.GitVersioning/ManagedGit/GitRepository.cs

@@ -28,7 +28,7 @@ public class GitRepository : IDisposable
 
         private readonly List<GitRepository> alternates = new List<GitRepository>();
 
-#if DEBUG && !NETSTANDARD
+#if DEBUG
         private Dictionary<GitObjectId, int> histogram = new Dictionary<GitObjectId, int>();
 #endif
 
@@ -524,7 +524,7 @@ public GitObjectId GetTreeEntry(GitObjectId treeId, ReadOnlySpan<byte> nodeName)
         /// </returns>
         public bool TryGetObjectBySha(GitObjectId sha, string objectType, out Stream? value)
         {
-#if DEBUG && !NETSTANDARD
+#if DEBUG
             if (!this.histogram.TryAdd(sha, 1))
             {
                 this.histogram[sha] += 1;
@@ -566,7 +566,7 @@ public string GetCacheStatistics()
         {
             StringBuilder builder = new StringBuilder();
 
-#if DEBUG && !NETSTANDARD
+#if DEBUG
             int histogramCount = 25;
 
             builder.AppendLine("Overall repository:");
@@ -659,7 +659,7 @@ private ReadOnlyMemory<GitPack> LoadPacks()
 
         private static string TrimEndingDirectorySeparator(string path)
         {
-#if NETSTANDARD
+#if NETSTANDARD2_0
             if (string.IsNullOrEmpty(path) || path.Length == 1)
             {
                 return path;
@@ -690,7 +690,7 @@ private static bool TryConvertHexStringToByteArray(string hexString, Span<byte>
             Requires.Argument(data.Length == hexString.Length / 2, nameof(data), "Length must be exactly half that of " + nameof(hexString) + ".");
             for (int index = 0; index < data.Length; index++)
             {
-#if NETCOREAPP3_1_OR_GREATER
+#if !NETSTANDARD2_0
                 ReadOnlySpan<char> byteValue = hexString.AsSpan(index * 2, 2);
                 if (!byte.TryParse(byteValue, NumberStyles.HexNumber, CultureInfo.InvariantCulture, out data[index]))
                 {

src/NerdBank.GitVersioning/ManagedGit/MemoryMappedStream.cs

@@ -72,7 +72,7 @@ public override int Read(byte[] buffer, int offset, int count)
             return read;
         }
 
-#if !NETSTANDARD
+#if !NETSTANDARD2_0
         /// <inheritdoc/>
         public override int Read(Span<byte> buffer)
         {

src/NerdBank.GitVersioning/ManagedGit/StreamExtensions.cs

@@ -2,7 +2,6 @@
 
 using System;
 using System.Buffers;
-using System.Diagnostics;
 using System.IO;
 
 namespace Nerdbank.GitVersioning.ManagedGit
@@ -78,7 +77,7 @@ public static int ReadMbsInt(this Stream stream)
             return value;
         }
 
-#if NETSTANDARD
+#if NETSTANDARD2_0
         /// <summary>
         /// Reads a sequence of bytes from the current stream and advances the position within the stream by
         /// the number of bytes read.
@@ -139,6 +138,17 @@ public static void Write(this Stream stream, Span<byte> span)
                 ArrayPool<byte>.Shared.Return(buffer);
             }
         }
+
+        internal static bool TryAdd<TKey, TValue>(this System.Collections.Generic.IDictionary<TKey, TValue> dictionary, TKey key, TValue value)
+        {
+            if (dictionary.ContainsKey(key))
+            {
+                return false;
+            }
+
+            dictionary.Add(key, value);
+            return true;
+        }
 #endif
     }
 }

src/NerdBank.GitVersioning/ManagedGit/ZLibStream.cs

@@ -94,7 +94,7 @@ public override int Read(byte[] array, int offset, int count)
             return read;
         }
 
-#if !NETSTANDARD
+#if !NETSTANDARD2_0
         /// <inheritdoc/>
         public override int Read(Span<byte> buffer)
         {
@@ -112,7 +112,7 @@ public override async Task<int> ReadAsync(byte[] array, int offset, int count, C
             return read;
         }
 
-#if !NETSTANDARD
+#if !NETSTANDARD2_0
         /// <inheritdoc/>
         public override async ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default)
         {