project: reorganize the structure of the project.

* remove dotnet-tool.json because the project does not rely on any dotnet tools.
* remove Directory.Build.props because the solution has only one project.
* move src/SourceGit to src. It's not needed to put all sources into a subfolder of src since there's only one project.

src/Commands/Push.cs

@@ -0,0 +1,89 @@
+using System;
+
+namespace SourceGit.Commands
+{
+    public class Push : Command
+    {
+        public Push(string repo, string local, string remote, string remoteBranch, bool withTags, bool force, bool track, Action<string> onProgress)
+        {
+            WorkingDirectory = repo;
+            Context = repo;
+            TraitErrorAsOutput = true;
+            _outputHandler = onProgress;
+
+            var sshKey = new Config(repo).Get($"remote.{remote}.sshkey");
+            if (!string.IsNullOrEmpty(sshKey))
+            {
+                Args = $"-c core.sshCommand=\"ssh -i '{sshKey}'\" ";
+            }
+            else
+            {
+                Args = "-c credential.helper=manager ";
+            }
+
+            Args += "push --progress --verbose ";
+
+            if (withTags)
+                Args += "--tags ";
+            if (track)
+                Args += "-u ";
+            if (force)
+                Args += "--force-with-lease ";
+
+            Args += $"{remote} {local}:{remoteBranch}";
+        }
+
+        /// <summary>
+        ///     Only used to delete a remote branch!!!!!!
+        /// </summary>
+        /// <param name="repo"></param>
+        /// <param name="remote"></param>
+        /// <param name="branch"></param>
+        public Push(string repo, string remote, string branch)
+        {
+            WorkingDirectory = repo;
+            Context = repo;
+            TraitErrorAsOutput = true;
+
+            var sshKey = new Config(repo).Get($"remote.{remote}.sshkey");
+            if (!string.IsNullOrEmpty(sshKey))
+            {
+                Args = $"-c core.sshCommand=\"ssh -i '{sshKey}'\" ";
+            }
+            else
+            {
+                Args = "-c credential.helper=manager ";
+            }
+
+            Args += $"push {remote} --delete {branch}";
+        }
+
+        public Push(string repo, string remote, string tag, bool isDelete)
+        {
+            WorkingDirectory = repo;
+            Context = repo;
+
+            var sshKey = new Config(repo).Get($"remote.{remote}.sshkey");
+            if (!string.IsNullOrEmpty(sshKey))
+            {
+                Args = $"-c core.sshCommand=\"ssh -i '{sshKey}'\" ";
+            }
+            else
+            {
+                Args = "-c credential.helper=manager ";
+            }
+
+            Args += "push ";
+            if (isDelete)
+                Args += "--delete ";
+            Args += $"{remote} refs/tags/{tag}";
+        }
+
+        protected override void OnReadline(string line)
+        {
+            _outputHandler?.Invoke(line);
+        }
+
+        private readonly Action<string> _outputHandler = null;
+    }
+}