feat(model-client): allow deleting branches

Adds a new `deleteBranch` method to IModelClientV2 for deleting a branch
from a repository in case it exists.

Author: languitar

model-client/src/commonMain/kotlin/org/modelix/model/client2/IModelClientV2.kt

@@ -44,6 +44,14 @@ interface IModelClientV2 {
     suspend fun deleteRepository(repository: RepositoryId): Boolean
     suspend fun listBranches(repository: RepositoryId): List<BranchReference>
 
+    /**
+     * Deletes a branch from a repository if it exists.
+     *
+     * @param branch the branch to delete
+     * @return true if the branch existed and could be deleted, else false.
+     */
+    suspend fun deleteBranch(branch: BranchReference): Boolean
+
     @Deprecated("repository ID is required for permission checks")
     @DeprecationInfo("3.7.0", "May be removed with the next major release. Also remove the endpoint from the model-server.")
     suspend fun loadVersion(versionHash: String, baseVersion: IVersion?): IVersion

model-client/src/commonMain/kotlin/org/modelix/model/client2/ModelClientV2.kt

@@ -22,6 +22,7 @@ import io.ktor.client.plugins.ResponseException
 import io.ktor.client.plugins.contentnegotiation.ContentNegotiation
 import io.ktor.client.plugins.expectSuccess
 import io.ktor.client.request.HttpRequestBuilder
+import io.ktor.client.request.delete
 import io.ktor.client.request.get
 import io.ktor.client.request.post
 import io.ktor.client.request.prepareGet
@@ -168,6 +169,25 @@ class ModelClientV2(
         }.bodyAsText().lines().filter { it.isNotEmpty() }.map { repository.getBranchReference(it) }
     }
 
+    override suspend fun deleteBranch(branch: BranchReference): Boolean {
+        try {
+            return httpClient.delete {
+                url {
+                    takeFrom(baseUrl)
+                    appendPathSegmentsEncodingSlash(
+                        "repositories",
+                        branch.repositoryId.id,
+                        "branches",
+                        branch.branchName,
+                    )
+                }
+            }.status == HttpStatusCode.NoContent
+        } catch (ex: Exception) {
+            LOG.error(ex) { ex.message }
+            return false
+        }
+    }
+
     @Deprecated("repository ID is required for permission checks")
     @DeprecationInfo("3.7.0", "May be removed with the next major release. Also remove the endpoint from the model-server.")
     override suspend fun loadVersion(versionHash: String, baseVersion: IVersion?): IVersion {

model-server/src/test/kotlin/org/modelix/model/server/ModelClientV2Test.kt

@@ -24,6 +24,7 @@ import org.modelix.model.api.PBranch
 import org.modelix.model.client2.ModelClientV2
 import org.modelix.model.client2.runWrite
 import org.modelix.model.client2.runWriteOnBranch
+import org.modelix.model.lazy.BranchReference
 import org.modelix.model.lazy.CLTree
 import org.modelix.model.lazy.CLVersion
 import org.modelix.model.lazy.RepositoryId
@@ -165,6 +166,47 @@ class ModelClientV2Test {
         assertFalse(containsRepository)
     }
 
+    @Test
+    fun `branches from non-existing repositories cannot be removed`() = runTest {
+        val client = createModelClient()
+        val repositoryId = RepositoryId(UUID.randomUUID().toString())
+
+        val success = client.deleteBranch(BranchReference(repositoryId, "doesntmatter"))
+
+        assertFalse(success)
+    }
+
+    @Test
+    fun `non-existing branches from existing repositories cannot be removed`() = runTest {
+        val client = createModelClient()
+        val repositoryId = RepositoryId(UUID.randomUUID().toString())
+        client.initRepository(repositoryId)
+
+        val success = client.deleteBranch(BranchReference(repositoryId, "doesnotexist"))
+
+        assertFalse(success)
+    }
+
+    @Test
+    fun `existing branches from existing repositories can be removed`() = runTest {
+        val client = createModelClient()
+        val repositoryId = RepositoryId(UUID.randomUUID().toString())
+        client.initRepository(repositoryId)
+        val branchToDelete = BranchReference(repositoryId, "todelete")
+        client.push(
+            branchToDelete,
+            requireNotNull(
+                client.pullIfExists(BranchReference(repositoryId, "master")),
+            ) { "the master branch must always exist" },
+            null,
+        )
+
+        val success = client.deleteBranch(BranchReference(repositoryId, branchToDelete.branchName))
+
+        assertTrue(success)
+        assertFalse(client.listBranches(repositoryId).contains(branchToDelete))
+    }
+
     @Test
     fun `pulling existing versions pulls all referenced objects`() = runTest {
         // Arrange