Added GitVersionException to wrap LibGit2Sharp.NotFoundException when the repository might be a shallow clone

Author: asbjornu

src/GitVersionCore/GitVersionCore.csproj

@@ -118,6 +118,7 @@
     <Compile Include="GitVersionCache.cs" />
     <Compile Include="GitVersionCacheKey.cs" />
     <Compile Include="GitVersionCacheKeyFactory.cs" />
+    <Compile Include="GitVersionException.cs" />
     <Compile Include="Helpers\EncodingHelper.cs" />
     <Compile Include="Helpers\FileSystem.cs" />
     <Compile Include="Helpers\IFileSystem.cs" />

src/GitVersionCore/GitVersionException.cs

@@ -0,0 +1,31 @@
+namespace GitVersion
+{
+    using System;
+    using System.Runtime.Serialization;
+
+    [Serializable]
+    public class GitVersionException : ApplicationException
+    {
+        public GitVersionException()
+        {
+        }
+
+
+        public GitVersionException(string message)
+            : base(message)
+        {
+        }
+
+
+        public GitVersionException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+
+
+        protected GitVersionException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}

src/GitVersionCore/VersionCalculation/FallbackBaseVersionStrategy.cs

@@ -14,11 +14,22 @@ public class FallbackBaseVersionStrategy : BaseVersionStrategy
     {
         public override IEnumerable<BaseVersion> GetVersions(GitVersionContext context)
         {
-            var baseVersionSource = context.Repository.Commits.QueryBy(new CommitFilter
+            Commit baseVersionSource;
+            var currentBranchTip = context.CurrentBranch.Tip;
+
+            try
+            {
+                baseVersionSource = context.Repository.Commits.QueryBy(new CommitFilter
+                {
+                    IncludeReachableFrom = currentBranchTip
+                }).First(c => !c.Parents.Any());
+            }
+            catch (NotFoundException exception)
             {
-                IncludeReachableFrom = context.CurrentBranch.Tip
-            }).First(c => !c.Parents.Any());
-            yield return new BaseVersion(context, "Fallback base version", false, new SemanticVersion(minor: 1), baseVersionSource, null);
+                throw new GitVersionException($"Can't find commit {currentBranchTip.Sha}. Please ensure that the repository is an unshallow clone with `git fetch --unshallow`.", exception);
+            }
+
+            yield return new BaseVersion(context, "Fallback base version", false, new SemanticVersion(minor : 1), baseVersionSource, null);
         }
     }
 }