From ed98a51109e8dea8f341177b84b14878891a61dc Mon Sep 17 00:00:00 2001
From: Kendall Bennett <kendallb@amain.com>
Date: Sat, 12 Mar 2022 15:40:01 -0500
Subject: [PATCH] Set the timestamp when the file is uploaded, and clear the
 milliseconds value which will not be passwed over the wire.

---
 src/Renci.SshNet/SftpClient.cs | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/Renci.SshNet/SftpClient.cs b/src/Renci.SshNet/SftpClient.cs
index d33e21816..67e4df95b 100644
--- a/src/Renci.SshNet/SftpClient.cs
+++ b/src/Renci.SshNet/SftpClient.cs
@@ -2110,6 +2110,8 @@ private IEnumerable<FileInfo> InternalSynchronizeDirectories(string sourcePath,
             const Flags uploadFlag = Flags.Write | Flags.Truncate | Flags.CreateNewOrOpen;
             foreach (var localFile in sourceFiles)
             {
+                // Clear the milliseconds from the timestamp, as that granularity will not carry over the wire with SFTP
+                var lastWriteTimeUtc = ClearMilliseconds(localFile.LastWriteTimeUtc);
                 var isDifferent = !destDict.ContainsKey(localFile.Name);
 
                 if (!isDifferent)
@@ -2117,7 +2119,8 @@ private IEnumerable<FileInfo> InternalSynchronizeDirectories(string sourcePath,
                     var temp = destDict[localFile.Name];
                     //  TODO:   Use md5 to detect a difference
                     //ltang: File exists at the destination => Using filesize to detect the difference
-                    isDifferent = localFile.Length != temp.Length;
+                    //kendallb: Use file length and timestamp to detect the difference
+                    isDifferent = localFile.Length != temp.Length || lastWriteTimeUtc != localFile.LastWriteTimeUtc;
                 }
 
                 if (isDifferent)
@@ -2128,6 +2131,11 @@ private IEnumerable<FileInfo> InternalSynchronizeDirectories(string sourcePath,
                         using (var file = File.OpenRead(localFile.FullName))
                         {
                             InternalUploadFile(file, remoteFileName, uploadFlag, null, null);
+
+                            // Set the timestamp to match on the uploaded file (the helper function is not implemented in the library)
+                            var fileAttributes = GetAttributes(remoteFileName);
+                            fileAttributes.LastWriteTimeUtc = lastWriteTimeUtc;
+                            SetAttributes(remoteFileName, fileAttributes);
                         }
 
                         uploadedFiles.Add(localFile);
@@ -2149,6 +2157,17 @@ private IEnumerable<FileInfo> InternalSynchronizeDirectories(string sourcePath,
             return uploadedFiles;
         }
 
+        /// <summary>
+        /// Utility function to clear the millisecond value for a DateTime stamp
+        /// </summary>
+        /// <param name="date">Date to adjust</param>
+        /// <returns>Adjusted DateTime value</returns>
+        private static DateTime ClearMilliseconds(
+            DateTime date)
+        {
+            return new DateTime(date.Year, date.Month, date.Day, date.Hour, date.Minute, date.Second, date.Kind);
+        }
+
         #endregion
 
         /// <summary>