feat: support multi-branching within Studio

src/Designer/backend/src/Designer/Controllers/RepositoryController.cs

@@ -400,6 +400,69 @@ public async Task<ActionResult<List<Branch>>> Branches(string org, string reposi
             }
         }
 
+        /// <summary>
+        /// Creates a new branch in the repository
+        /// </summary>
+        /// <param name="org">Unique identifier of the organisation responsible for the app.</param>
+        /// <param name="repository">The name of repository</param>
+        /// <param name="request">The branch creation request</param>
+        /// <returns>The created branch</returns>
+        [HttpPost]
+        [Route("repo/{org}/{repository:regex(^(?!datamodels$)[[a-z]][[a-z0-9-]]{{1,28}}[[a-z0-9]]$)}/branches")]
+        public async Task<ActionResult<Branch>> CreateBranch(string org, string repository, [FromBody] CreateBranchRequest request)
+        {
+            var branch = await _sourceControl.CreateBranch(org, repository, request.BranchName);
+            return Ok(branch);
+        }
+
+        /// <summary>
+        /// Gets information about the current branch
+        /// </summary>
+        /// <param name="org">Unique identifier of the organisation responsible for the app.</param>
+        /// <param name="repository">The name of repository</param>
+        /// <returns>Information about the current branch</returns>
+        [HttpGet]
+        [Route("repo/{org}/{repository:regex(^(?!datamodels$)[[a-z]][[a-z0-9-]]{{1,28}}[[a-z0-9]]$)}/current-branch")]
+        public ActionResult<CurrentBranchInfo> GetCurrentBranch(string org, string repository)
+        {
+            var branchInfo = _sourceControl.GetCurrentBranch(org, repository);
+            return Ok(branchInfo);
+        }
+
+        /// <summary>
+        /// Checks out a specific branch
+        /// </summary>
+        /// <param name="org">Unique identifier of the organisation responsible for the app.</param>
+        /// <param name="repository">The name of repository</param>
+        /// <param name="request">The checkout request</param>
+        /// <returns>The updated repository status</returns>
+        [HttpPost]
+        [Route("repo/{org}/{repository:regex(^(?!datamodels$)[[a-z]][[a-z0-9-]]{{1,28}}[[a-z0-9]]$)}/checkout")]
+        public async Task<ActionResult<RepoStatus>> CheckoutBranch(string org, string repository, [FromBody] CheckoutBranchRequest request)
+        {
+            if (string.IsNullOrWhiteSpace(request?.BranchName))
+            {
+                return BadRequest("Branch name is required");
+            }
+
+            var repoStatus = await _sourceControl.CheckoutBranchWithValidation(org, repository, request.BranchName);
+            return Ok(repoStatus);
+        }
+
+        /// <summary>
+        /// Discards all local changes in the repository
+        /// </summary>
+        /// <param name="org">Unique identifier of the organisation responsible for the app.</param>
+        /// <param name="repository">The name of repository</param>
+        /// <returns>The updated repository status</returns>
+        [HttpPost]
+        [Route("repo/{org}/{repository:regex(^(?!datamodels$)[[a-z]][[a-z0-9-]]{{1,28}}[[a-z0-9]]$)}/discard-changes")]
+        public ActionResult<RepoStatus> DiscardLocalChanges(string org, string repository)
+        {
+            var repoStatus = _sourceControl.DiscardLocalChanges(org, repository);
+            return Ok(repoStatus);
+        }
+
         /// <summary>
         /// Stages a specific file changed in working repository.
         /// </summary>

src/Designer/backend/src/Designer/Exceptions/UncommittedChangesException.cs

@@ -0,0 +1,26 @@
+using System;
+using Altinn.Studio.Designer.Models;
+
+namespace Altinn.Studio.Designer.Exceptions
+{
+    /// <summary>
+    /// Exception thrown when attempting to checkout a branch with uncommitted changes
+    /// </summary>
+    public class UncommittedChangesException : Exception
+    {
+        /// <summary>
+        /// Gets the uncommitted changes error details
+        /// </summary>
+        public UncommittedChangesError ErrorDetails { get; }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UncommittedChangesException"/> class.
+        /// </summary>
+        /// <param name="errorDetails">The uncommitted changes error details</param>
+        public UncommittedChangesException(UncommittedChangesError errorDetails)
+            : base(errorDetails.Message)
+        {
+            ErrorDetails = errorDetails;
+        }
+    }
+}

src/Designer/backend/src/Designer/Filters/Git/GitErrorCodes.cs

@@ -6,5 +6,7 @@ public class GitErrorCodes
         public const string NonFastForwardError = "GT_01";
         public const string RepositoryNotFound = "GT_02";
         public const string GiteaSessionExpired = "GT_03";
+        public const string UncommittedChanges = "GT_04";
+        public const string BranchNotFound = "GT_05";
     }
 }

src/Designer/backend/src/Designer/Filters/Git/GitExceptionFilterAttribute.cs

@@ -33,6 +33,12 @@ public override void OnException(ExceptionContext context)
             {
                 context.Result = new ObjectResult(ProblemDetailsUtils.GenerateProblemDetails(context.Exception, GitErrorCodes.GiteaSessionExpired, HttpStatusCode.Unauthorized)) { StatusCode = (int)HttpStatusCode.Unauthorized };
             }
+
+            if (context.Exception is Exceptions.UncommittedChangesException uncommittedChangesException)
+            {
+                context.Result = new ObjectResult(uncommittedChangesException.ErrorDetails) { StatusCode = (int)HttpStatusCode.Conflict };
+                context.ExceptionHandled = true;
+            }
         }
     }
 }

src/Designer/backend/src/Designer/Helpers/InputValidator.cs

@@ -1,6 +1,7 @@
 using System.Text.RegularExpressions;
 
 namespace Altinn.Studio.Designer.Helpers;
+
 public static partial class InputValidator
 {
 

src/Designer/backend/src/Designer/Models/BranchModels.cs

@@ -0,0 +1,103 @@
+#nullable disable
+namespace Altinn.Studio.Designer.Models
+{
+    /// <summary>
+    /// Request model for creating a new branch
+    /// </summary>
+    public class CreateBranchRequest
+    {
+        /// <summary>
+        /// Gets or sets the name of the branch to create
+        /// </summary>
+        public string BranchName { get; set; }
+    }
+
+    /// <summary>
+    /// Request model for checking out a branch
+    /// </summary>
+    public class CheckoutBranchRequest
+    {
+        /// <summary>
+        /// Gets or sets the name of the branch to checkout
+        /// </summary>
+        public string BranchName { get; set; }
+    }
+
+    /// <summary>
+    /// Information about the current branch
+    /// </summary>
+    public class CurrentBranchInfo
+    {
+        /// <summary>
+        /// Gets or sets the name of the current branch
+        /// </summary>
+        public string BranchName { get; set; }
+
+        /// <summary>
+        /// Gets or sets the SHA of the current commit
+        /// </summary>
+        public string CommitSha { get; set; }
+
+        /// <summary>
+        /// Gets or sets whether the branch is tracking a remote branch
+        /// </summary>
+        public bool IsTracking { get; set; }
+
+        /// <summary>
+        /// Gets or sets the name of the tracked remote branch
+        /// </summary>
+        public string RemoteName { get; set; }
+    }
+
+    /// <summary>
+    /// Error response for uncommitted changes
+    /// </summary>
+    public class UncommittedChangesError
+    {
+        /// <summary>
+        /// Gets or sets the error code
+        /// </summary>
+        public string ErrorCode { get; set; } = Filters.Git.GitErrorCodes.UncommittedChanges;
+
+        /// <summary>
+        /// Gets or sets the error type
+        /// </summary>
+        public string Error { get; set; }
+
+        /// <summary>
+        /// Gets or sets the error message
+        /// </summary>
+        public string Message { get; set; }
+
+        /// <summary>
+        /// Gets or sets the list of uncommitted files
+        /// </summary>
+        public System.Collections.Generic.List<UncommittedFile> UncommittedFiles { get; set; }
+
+        /// <summary>
+        /// Gets or sets the current branch name
+        /// </summary>
+        public string CurrentBranch { get; set; }
+
+        /// <summary>
+        /// Gets or sets the target branch name
+        /// </summary>
+        public string TargetBranch { get; set; }
+    }
+
+    /// <summary>
+    /// Information about an uncommitted file
+    /// </summary>
+    public class UncommittedFile
+    {
+        /// <summary>
+        /// Gets or sets the file path
+        /// </summary>
+        public string FilePath { get; set; }
+
+        /// <summary>
+        /// Gets or sets the file status
+        /// </summary>
+        public string Status { get; set; }
+    }
+}

src/Designer/backend/src/Designer/Models/CommitInfo.cs

@@ -20,5 +20,10 @@ public class CommitInfo
         /// Gets or sets the repository name
         /// </summary>
         public string Repository { get; set; }
+
+        /// <summary>
+        /// Gets or sets the branch name to commit to
+        /// </summary>
+        public string BranchName { get; set; }
     }
 }

src/Designer/backend/src/Designer/Models/FooterFile.cs

@@ -5,6 +5,7 @@
 using JetBrains.Annotations;
 
 namespace Altinn.Studio.Designer.Models;
+
 public class FooterFile
 {
     [JsonPropertyName("$schema")]

src/Designer/backend/src/Designer/Models/RepoStatus.cs

@@ -36,5 +36,10 @@ public class RepoStatus
         /// Defines if there is any merge conflicts
         /// </summary>
         public bool HasMergeConflict { get; set; }
+
+        /// <summary>
+        /// The current branch name
+        /// </summary>
+        public string CurrentBranch { get; set; }
     }
 }

src/Designer/backend/src/Designer/Services/Implementation/SourceControlLoggingDecorator.cs

@@ -393,6 +393,48 @@ private void LogError(Exception ex, string method)
             LogError(ex, method, string.Empty, string.Empty);
         }
 
+        /// <inheritdoc/>
+        public CurrentBranchInfo GetCurrentBranch(string org, string repository)
+        {
+            try
+            {
+                return _decoratedService.GetCurrentBranch(org, repository);
+            }
+            catch (Exception ex)
+            {
+                LogError(ex, "GetCurrentBranch", org, repository);
+                throw;
+            }
+        }
+
+        /// <inheritdoc/>
+        public async Task<RepoStatus> CheckoutBranchWithValidation(string org, string repository, string branchName)
+        {
+            try
+            {
+                return await _decoratedService.CheckoutBranchWithValidation(org, repository, branchName);
+            }
+            catch (Exception ex)
+            {
+                LogError(ex, "CheckoutBranchWithValidation", org, repository, repository, branchName);
+                throw;
+            }
+        }
+
+        /// <inheritdoc/>
+        public RepoStatus DiscardLocalChanges(string org, string repository)
+        {
+            try
+            {
+                return _decoratedService.DiscardLocalChanges(org, repository);
+            }
+            catch (Exception ex)
+            {
+                LogError(ex, "DiscardLocalChanges", org, repository);
+                throw;
+            }
+        }
+
         private void LogError(Exception ex, string method, string org, string repository)
         {
             LogError(ex, method, org, repository, repository, string.Empty);