From c51939831ef44d2f9eae57662f04121755f0ef69 Mon Sep 17 00:00:00 2001
From: Martin Nonnenmacher <martin.nonnenmacher@bosch.io>
Date: Thu, 21 Sep 2023 15:33:06 +0200
Subject: [PATCH] fix(downloader): Fix updating the Git working tree for a
 branch

The `Git.updateWorkingTree` function called only `git checkout
$revision` after fetching. In case of a local branch that was already
cloned before, this did not update the local branch.

Fix this by calling `git reset --hard FETCH_HEAD` after the checkout if
the revision is not a fixed revision.

Signed-off-by: Martin Nonnenmacher <martin.nonnenmacher@bosch.io>
---
 .../src/funTest/kotlin/vcs/GitFunTest.kt      | 95 +++++++++++++++++++
 downloader/src/main/kotlin/vcs/Git.kt         |  6 ++
 2 files changed, 101 insertions(+)
 create mode 100644 downloader/src/funTest/kotlin/vcs/GitFunTest.kt

diff --git a/downloader/src/funTest/kotlin/vcs/GitFunTest.kt b/downloader/src/funTest/kotlin/vcs/GitFunTest.kt
new file mode 100644
index 0000000000000..fe47eb1f8436f
--- /dev/null
+++ b/downloader/src/funTest/kotlin/vcs/GitFunTest.kt
@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2023 The ORT Project Authors (see <https://github.com/oss-review-toolkit/ort/blob/main/NOTICE>)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * License-Filename: LICENSE
+ */
+
+package org.ossreviewtoolkit.downloader.vcs
+
+import io.kotest.core.spec.style.WordSpec
+import io.kotest.engine.spec.tempdir
+import io.kotest.matchers.result.shouldBeSuccess
+import io.kotest.matchers.shouldBe
+
+import java.io.File
+
+import org.ossreviewtoolkit.downloader.WorkingTree
+import org.ossreviewtoolkit.model.VcsInfo
+import org.ossreviewtoolkit.model.VcsType
+
+private val branches = mapOf(
+    "main" to "6f09f276c4426c387c6663f54bbd45aea8d81dac",
+    "branch1" to "0c58ea81d5c8112affab7a9cd6308deb4bc51589",
+    "branch2" to "7a05ad3ad30b4ddbfac22e0b768fb91383f16d8d",
+    "branch3" to "b798693a551e4d0e96d09409948327178a9abbce"
+)
+
+private val tags = mapOf(
+    "tag1" to "0c58ea81d5c8112affab7a9cd6308deb4bc51589",
+    "tag2" to "7a05ad3ad30b4ddbfac22e0b768fb91383f16d8d",
+    "tag3" to "b798693a551e4d0e96d09409948327178a9abbce"
+)
+
+class GitFunTest : WordSpec({
+    val git = Git()
+    val vcsInfo = VcsInfo(
+        type = VcsType.GIT,
+        url = "https://github.com/oss-review-toolkit/ort-test-data-git.git",
+        revision = "main"
+    )
+
+    lateinit var repoDir: File
+    lateinit var workingTree: WorkingTree
+
+    beforeEach {
+        repoDir = tempdir()
+        workingTree = git.initWorkingTree(repoDir, vcsInfo)
+    }
+
+    "updateWorkingTree" should {
+        "update the working tree to the correct revision" {
+            branches.values.forEach { revision ->
+                git.updateWorkingTree(workingTree, revision) shouldBeSuccess revision
+                workingTree.getRevision() shouldBe revision
+            }
+        }
+
+        "update the working tree to the correct tag" {
+            tags.forEach { (tag, revision) ->
+                git.updateWorkingTree(workingTree, tag) shouldBeSuccess tag
+                workingTree.getRevision() shouldBe revision
+            }
+        }
+
+        "update the working tree to the correct branch" {
+            branches.forEach { (branch, revision) ->
+                git.updateWorkingTree(workingTree, branch) shouldBeSuccess branch
+                workingTree.getRevision() shouldBe revision
+            }
+        }
+
+        "update an outdated local branch" {
+            val branch = "branch1"
+            val revision = branches.getValue(branch)
+
+            git.updateWorkingTree(workingTree, branch)
+            git.run("reset", "--hard", "HEAD~1", workingDir = repoDir)
+
+            git.updateWorkingTree(workingTree, branch) shouldBeSuccess branch
+            workingTree.getRevision() shouldBe revision
+        }
+    }
+})
diff --git a/downloader/src/main/kotlin/vcs/Git.kt b/downloader/src/main/kotlin/vcs/Git.kt
index 7c3b6771e3168..7953f8839123c 100644
--- a/downloader/src/main/kotlin/vcs/Git.kt
+++ b/downloader/src/main/kotlin/vcs/Git.kt
@@ -239,6 +239,12 @@ class Git : VersionControlSystem(), CommandLineTool {
             // TODO: Migrate this to JGit once https://bugs.eclipse.org/bugs/show_bug.cgi?id=383772 is implemented.
             run("checkout", revision, workingDir = workingTree.workingDir)
 
+            // In case of a non-fixed revision (branch or tag) reset the working tree to ensure that the previously
+            // fetched changes are applied.
+            if (!isFixedRevision(workingTree, revision).getOrThrow()) {
+                run("reset", "--hard", "FETCH_HEAD", workingDir = workingTree.workingDir)
+            }
+
             revision
         }