Add tests of various lengths of partial commit matching

Author: AArnott

src/NerdBank.GitVersioning.Tests/GitContextTests.cs

@@ -85,10 +85,15 @@ public void SelectCommitByPartialId(bool fromPack)
         Assert.Equal(this.LibGit2Repository.Head.Tip.Sha, this.Context.GitCommitId);
     }
 
-    [Fact]
-    public void GetShortUniqueCommitId()
+    [SkippableTheory]
+    [InlineData(4)]
+    [InlineData(7)]
+    [InlineData(8)]
+    [InlineData(11)]
+    public void GetShortUniqueCommitId(int length)
     {
-        Assert.Equal("51cd9ed3", this.Context.GetShortUniqueCommitId(8));
+        Skip.If(length < 7 && this.Context is Nerdbank.GitVersioning.LibGit2.LibGit2Context);
+        Assert.Equal(this.Context.GitCommitId.Substring(0, length), this.Context.GetShortUniqueCommitId(length));
     }
 
     [Theory, CombinatorialData]

src/NerdBank.GitVersioning.Tests/VersionOracleTests.cs

@@ -795,15 +795,22 @@ public void GetVersionHeight_ProjectDirectoryIsMoved()
     }
 
     [Fact]
-    public void OptimallyShortCommitId()
+    public void GitCommitIdShort()
     {
         this.WriteVersionFile(new VersionOptions { Version = SemanticVersion.Parse("1.2"), GitCommitIdShortAutoMinimum = 4 });
         this.InitializeSourceControl();
         this.AddCommits(1);
         var oracle = new VersionOracle(this.Context);
 
-        // I'm not sure why libgit2 returns 7 as the minimum length when clearly a two commit repo would need fewer.
-        Assert.Equal(7, oracle.GitCommitIdShort.Length);
+        if (this.Context is Nerdbank.GitVersioning.LibGit2.LibGit2Context)
+        {
+            // I'm not sure why libgit2 returns 7 as the minimum length when clearly a two commit repo would need fewer.
+            Assert.Equal(7, oracle.GitCommitIdShort.Length);
+        }
+        else
+        {
+            Assert.Equal(4, oracle.GitCommitIdShort.Length);
+        }
     }
 
     [Fact(Skip = "Slow test")]