refactor: commit message

- move issue tracker and commit hash links parsing to view models
- parsing links async
- make sure matched hash is a valid commit oid
- disable `CHILDREN` row in submodule info panel

Signed-off-by: leo <longshuang@msn.cn>

src/ViewModels/DiffContext.cs

@@ -235,13 +235,17 @@ namespace SourceGit.ViewModels
             if (commit != null)
             {
                 var body = new Commands.QueryCommitFullMessage(repo, sha).Result();
-                return new Models.RevisionSubmodule() { Commit = commit, FullMessage = body };
+                return new Models.RevisionSubmodule()
+                {
+                    Commit = commit,
+                    FullMessage = new Models.CommitFullMessage { Message = body }
+                };
             }
 
             return new Models.RevisionSubmodule()
             {
                 Commit = new Models.Commit() { SHA = sha },
-                FullMessage = string.Empty,
+                FullMessage = null,
             };
         }