Improve detection of merge parent

Fixes issue where the wrong parent is selected for a merge if the
correct parent consists entirely of files that were modified in earlier
changesets in the merge (it was selecting the highest "version FROM"
instead of "version TO").

doc/release-notes/NEXT.md

@@ -4,3 +4,4 @@
 * Add .net462 and windows10 long path support. See [doc to enable it](../blob/master/doc/Set-custom-workspace.md). (#1221 by @pmiossec)
 * Fix bug where checkin attempts to remove a non-empty directory. (#1249 by @m-akinc)
 * Line endings are now properly normalized when pushing changes to TFS if core.autocrlf is set to true (#1210 by @JeffCyr)
+* Fix merge commits connecting to wrong parent

src/GitTfs.VsCommon/TfsHelper.Common.cs

@@ -230,9 +230,10 @@ namespace GitTfs.VsCommon
             //  2. figuring out up to which changeset the merge source branch needs to be fetched
             return changes.Max(change =>
             {
-                if (change.MergeSources.Empty())
+                var mergeSources = change.MergeSources.Where(mergeSource => mergeSource.VersionTo < targetChangeset);
+                if (mergeSources.Empty())
                     return -1;
-                return change.MergeSources.Max(mergeSource => mergeSource.VersionFrom);
+                return mergeSources.Max(mergeSource => mergeSource.VersionTo);
             });
         }