Do not use string formatting LibGit2SharpException constructor when building unknown exception types

Author: Dylan Lerch

LibGit2Sharp/Core/Ensure.cs

@@ -148,7 +148,18 @@ private static unsafe void HandleError(int result)
             Func<string, GitErrorCategory, LibGit2SharpException> exceptionBuilder;
             if (!GitErrorsToLibGit2SharpExceptions.TryGetValue((GitErrorCode)result, out exceptionBuilder))
             {
-                exceptionBuilder = (m, c) => new LibGit2SharpException(m, c);
+                // The exception constructors in GitErrorsToLibGit2SharpExceptions make use of the error
+                // category by passing it through to the NativeException(string message, GitErrorCategory category)
+                // constructor which adds ("libgit2.category", category) to Data on System.Exception.
+                //
+                // We were calling new LibGit2SharpException(m, c) below, but this was resolving to the
+                // string formatting constructor on LibGit2SharpException, because it does not have a constructor
+                // that takes a category. This runs a string format, so if the errorMessage contained any curly
+                // braces, that constructor would throw an System.FormatException.
+                //
+                // This has been changed to just use the message constructor (with no format arguments), and will drop
+                // the error code (which is always Unknown anyway).
+                exceptionBuilder = (m, c) => new LibGit2SharpException(m);
             }
 
             throw exceptionBuilder(errorMessage, errorCategory);