Pound sign is now only allowed at the beginning of a line

Fixes fluentmigrator/fluentmigrator#859

Author: fubar-coder

FluentMigrator.BatchParser/RangeSearchers/PoundSignSingleLineComment.cs

@@ -14,19 +14,54 @@
 // limitations under the License.
 #endregion
 
+using System.Text.RegularExpressions;
+
 namespace FluentMigrator.BatchParser.RangeSearchers
 {
     /// <summary>
     /// A single line comment starting with a pound sign (<c># comment</c>)
     /// </summary>
-    public sealed class PoundSignSingleLineComment : SingleLineComment
+    public sealed class PoundSignSingleLineComment : IRangeSearcher
     {
+        private readonly Regex _startCodeRegex;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="PoundSignSingleLineComment"/> class.
         /// </summary>
         public PoundSignSingleLineComment()
-            : base("#")
         {
+            var startCode = "#";
+            _startCodeRegex = new Regex(Regex.Escape(startCode), RegexOptions.CultureInvariant | RegexOptions.Compiled);
+            StartCodeLength = startCode.Length;
+        }
+
+        /// <inheritdoc />
+        public int StartCodeLength { get; }
+
+        /// <inheritdoc />
+        public int EndCodeLength => 0;
+
+        /// <inheritdoc />
+        public bool IsComment => true;
+
+        /// <inheritdoc />
+        public int FindStartCode(ILineReader reader)
+        {
+            if (reader.Index != 0)
+                return -1;
+            var match = _startCodeRegex.Match(reader.Line, reader.Index);
+            if (!match.Success)
+                return -1;
+            var skippedText = reader.ReadString(match.Index - reader.Index);
+            if (!string.IsNullOrWhiteSpace(skippedText))
+                return -1;
+            return match.Index;
+        }
+
+        /// <inheritdoc />
+        public EndCodeSearchResult FindEndCode(ILineReader reader)
+        {
+            return reader.Line.Length;
         }
     }
 }