С голямо закъснение, но чак сега успях да го довърша:

---Commits Controller------------------------------

using Git.Data;
using Git.Data.Models;
using Git.Services;
using Git.ViewModels;
using Git.ViewModels.Commits;
using Git.ViewModels.Users;
using SUS.HTTP;
using SUS.MvcFramework;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Git.Controllers
{
    public class CommitsController : Controller
    {
        private readonly ApplicationDbContext data;
        private readonly IUsersService service;

        public CommitsController(ApplicationDbContext data, IUsersService service)
        {
            this.data = data;
            this.service = service;
        }

        public HttpResponse All()
        {
            if (this.IsUserSignedIn())
            {
                var commits = this.data.Commits
                .Where(c => c.CreatorId == this.GetUserId())
                .Select(c => new CommitListingModel
                {
                    Id = c.Id,
                    Repository = c.Repository.Name,
                    Description = c.Description,
                    CreatedOn = c.CreatedOn.ToString(),

                })
                .ToList();

                return this.View(commits);
            }

            return Error("You must sign in first.");
        }

        public HttpResponse Create(string id)
        {
            if (this.IsUserSignedIn())
            {
                var repo = this.data.Repositories
                .Where(r => r.Id == id)
                .Select(r => new CommitToRepoModel
                {
                    Id = r.Id,
                    Name = r.Name
                })
                .FirstOrDefault();

                if (repo == null)
                {
                    return Error("Repository does not exist.");
                }

                return this.View(repo);
            }
            else
            {
                return Error("You must sign in first!");
            }
            
        }

        [HttpPost]
        public HttpResponse Create(CreateCommitsModel model)
        {
            if (!this.data.Repositories.Any(r => r.Id == model.Id))
            {
                return Error("Repository not found.");
            }

            if (model.Description.Length < 5)
            {
                return Error("Commit description have be at least 5 characters.");
            }

            var commit = new Commit
            {
                Description = model.Description,
                CreatedOn = DateTime.UtcNow,
                CreatorId = this.GetUserId(),
                RepositoryId = model.Id
            };

            this.data.Commits.Add(commit);
            this.data.SaveChanges();

            return Redirect("/Repositories/All");
        }

        public HttpResponse Delete(string id)
        {
            var commit = this.data.Commits.Find(id);

            if (commit == null || commit.CreatorId != this.GetUserId())
            {
                return Error("Commit not found.");
            }

            this.data.Commits.Remove(commit);
            this.data.SaveChanges();

            return Redirect("/Commits/All");
        }
    }
}

---Commits Views------------------------------

using System;
using System.Collections.Generic;
using System.Text;

namespace Git.ViewModels.Commits
{
    public class CommitListingModel
    {
        public string Id { get; set; }

        public string Repository { get; set; }

        public string Description { get; set; }

        public string CreatedOn { get; set; }
    }
}

---------

using System;
using System.Collections.Generic;
using System.Text;

namespace Git.ViewModels.Commits
{
    public class CommitToRepoModel
    {
        public string  Id { get; set; }

        public string Name { get; set; }
    }
}

-------

using System;
using System.Collections.Generic;
using System.Text;

namespace Git.ViewModels.Commits
{
    public class CreateCommitsModel
    {
        public string Id { get; set; }

        public string Description { get; set; }
    }
}