From cf0b3d11237b8b85f35ea512f4c01238f285ab40 Mon Sep 17 00:00:00 2001
From: Ralf Hubert <ralf.hubert@secunet.com>
Date: Thu, 5 Sep 2024 11:25:56 +0200
Subject: [PATCH] git: do not move detached HEAD to attic if same commit

If a git-workspace is in a detached HEAD state and the recipe has been
updated to point to the same commit there is no need to move this into
attic.
---
 pym/bob/scm/git.py                   |  2 +-
 test/black-box/git-scm-switch/run.sh | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/pym/bob/scm/git.py b/pym/bob/scm/git.py
index d6b5073c8..53b22bfce 100644
--- a/pym/bob/scm/git.py
+++ b/pym/bob/scm/git.py
@@ -598,7 +598,7 @@ async def switch(self, invoker, oldScm):
 
             curCommit = await invoker.checkOutputCommand(["git", "rev-parse",
                 "HEAD"], cwd=self.__dir)
-            if curCommit != oldCommit:
+            if curCommit != oldCommit and curCommit != self.__commit:
                 invoker.fail("Cannot switch: user moved to different commit: {} vs. {}".format(curCommit, oldCommit))
 
         # Try to checkout new state in old workspace. If something fails the
diff --git a/test/black-box/git-scm-switch/run.sh b/test/black-box/git-scm-switch/run.sh
index b7ebcc807..6a679247a 100755
--- a/test/black-box/git-scm-switch/run.sh
+++ b/test/black-box/git-scm-switch/run.sh
@@ -185,3 +185,29 @@ run_bob dev -DSCM_DIR="$git_dir1" -DSCM_REV="$d1_c1" -DSCM_BRANCH=foobar root2 -
 ls -la dev/src/root2/1/workspace
 expect_output "hello world" cat dev/src/root2/1/workspace/test.txt
 expect_not_exist dev/src/root2/1/attic
+
+# detached HEAD handling
+cleanup
+run_bob dev -DSCM_DIR="$git_dir1" -DSCM_REV="$d1_c0" root
+
+# move to detached HEAD state
+pushd dev/src/root/1/workspace
+git checkout $d1_c1
+echo canary > canary.txt
+popd
+
+# run update to the same commit. No attic
+run_bob dev -DSCM_DIR="$git_dir1" -DSCM_REV="$d1_c1" root
+expect_not_exist dev/src/root/1/attic
+
+# commit the change and update to different commit -> attic
+pushd dev/src/root/1/workspace
+git config user.email "bob@bob.bob"
+git config user.name test
+git add .
+git commit -m "local commit"
+popd
+
+run_bob dev -DSCM_DIR="$git_dir1" -DSCM_REV="$d1_c2" root
+expect_not_exist dev/src/root/1/workspace/canary
+expect_exist dev/src/root/1/attic