fix checkout during bisect

pkg/commands/git_commands/bisect.go

@@ -97,6 +97,16 @@ func (self *BisectCommands) GetInfoForGitDir(gitDir string) *BisectInfo {
 	currentHash := strings.TrimSpace(string(currentContent))
 	info.current = currentHash
 
+	// Read actual HEAD to detect manual checkouts during bisect.
+	// During bisect, HEAD is always a detached hash (not a symbolic ref).
+	headContent, err := os.ReadFile(filepath.Join(gitDir, "HEAD"))
+	if err == nil {
+		headStr := strings.TrimSpace(string(headContent))
+		if !strings.HasPrefix(headStr, "ref: ") {
+			info.headHash = headStr
+		}
+	}
+
 	return info
 }
 

pkg/commands/git_commands/bisect_info.go

@@ -32,8 +32,13 @@ type BisectInfo struct {
 	// map of commit hashes to their status
 	statusMap map[string]BisectStatus
 
-	// the hash of the commit that's under test
+	// the hash of the commit that git bisect expects to be under test
+	// (from BISECT_EXPECTED_REV)
 	current string
+
+	// the actual HEAD hash, which may differ from current if the user
+	// manually checked out a different commit during bisect
+	headHash string
 }
 
 type BisectStatus int
@@ -63,6 +68,12 @@ func (self *BisectInfo) GetCurrentHash() string {
 	return self.current
 }
 
+// GetHeadHash returns the actual HEAD commit hash. During bisect this may
+// differ from GetCurrentHash() if the user manually checked out a commit.
+func (self *BisectInfo) GetHeadHash() string {
+	return self.headHash
+}
+
 func (self *BisectInfo) GetStartHash() string {
 	return self.start
 }

pkg/gui/controllers/bisect_controller.go

@@ -68,7 +68,13 @@ func (self *BisectController) openMidBisectMenu(info *git_commands.BisectInfo, c
 	// Originally we were allowing the user to, from the bisect menu, select whether
 	// they were talking about the selected commit or the current bisect commit,
 	// and that was a bit confusing (and required extra keypresses).
-	selectCurrentAfter := info.GetCurrentHash() == "" || info.GetCurrentHash() == commit.Hash()
+	// Use actual HEAD to determine the current commit, since the user may have
+	// manually checked out a different commit during bisect.
+	headHash := info.GetHeadHash()
+	if headHash == "" {
+		headHash = info.GetCurrentHash()
+	}
+	selectCurrentAfter := info.GetCurrentHash() == "" || headHash == commit.Hash()
 	// we need to wait to reselect if our bisect commits aren't ancestors of our 'start'
 	// ref, because we'll be reloading our commits in that case.
 	waitToReselect := selectCurrentAfter && !self.c.Git().Bisect.ReachableFromStart(info)
@@ -78,7 +84,7 @@ func (self *BisectController) openMidBisectMenu(info *git_commands.BisectInfo, c
 	// use the selected commit in that case.
 
 	bisecting := info.GetCurrentHash() != ""
-	hashToMark := lo.Ternary(bisecting, info.GetCurrentHash(), commit.Hash())
+	hashToMark := lo.Ternary(bisecting, headHash, commit.Hash())
 	shortHashToMark := utils.ShortHash(hashToMark)
 
 	// For marking a commit as bad, when we're not already bisecting, we require
@@ -130,7 +136,7 @@ func (self *BisectController) openMidBisectMenu(info *git_commands.BisectInfo, c
 			Key:            's',
 		},
 	}
-	if info.GetCurrentHash() != "" && info.GetCurrentHash() != commit.Hash() {
+	if info.GetCurrentHash() != "" && headHash != commit.Hash() {
 		menuItems = append(menuItems, lo.ToPtr(types.MenuItem{
 			Label: fmt.Sprintf(self.c.Tr.Bisect.SkipSelected, commit.ShortHash()),
 			OnPress: func() error {

pkg/gui/presentation/commits.go

@@ -287,7 +287,14 @@ func getBisectStatus(index int, commitHash string, bisectInfo *git_commands.Bise
 		return BisectStatusNone
 	}
 
-	if bisectInfo.GetCurrentHash() == commitHash {
+	// Use actual HEAD hash to determine the current position, since the user
+	// may have manually checked out a different commit during bisect.
+	// Fall back to BISECT_EXPECTED_REV if HEAD hash is not available.
+	currentHash := bisectInfo.GetHeadHash()
+	if currentHash == "" {
+		currentHash = bisectInfo.GetCurrentHash()
+	}
+	if currentHash == commitHash {
 		return BisectStatusCurrent
 	}
 

pkg/integration/tests/bisect/checkout_during_bisect.go

@@ -0,0 +1,83 @@
+package bisect
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var CheckoutDuringBisect = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Checkout a different commit during a bisect and verify the current marker follows HEAD",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupRepo: func(shell *Shell) {
+		shell.
+			NewBranch("mybranch").
+			CreateNCommits(10)
+	},
+	SetupConfig: func(cfg *config.AppConfig) {
+		cfg.GetUserConfig().Git.Log.ShowGraph = "never"
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Focus().
+			SelectedLine(Contains("CI commit 10")).
+			Press(keys.Commits.ViewBisectOptions).
+			Tap(func() {
+				t.ExpectPopup().Menu().Title(Equals("Bisect")).Select(MatchesRegexp(`Mark .* as bad`)).Confirm()
+			}).
+			NavigateToLine(Contains("CI commit 01")).
+			Press(keys.Commits.ViewBisectOptions).
+			Tap(func() {
+				t.ExpectPopup().Menu().Title(Equals("Bisect")).Select(MatchesRegexp(`Mark .* as good`)).Confirm()
+			}).
+			// bisect has auto-selected commit 05 as current
+			Lines(
+				Contains("CI commit 10").Contains("<-- bad"),
+				Contains("CI commit 09").DoesNotContain("<--"),
+				Contains("CI commit 08").DoesNotContain("<--"),
+				Contains("CI commit 07").DoesNotContain("<--"),
+				Contains("CI commit 06").DoesNotContain("<--"),
+				Contains("CI commit 05").Contains("<-- current").IsSelected(),
+				Contains("CI commit 04").DoesNotContain("<--"),
+				Contains("CI commit 03").DoesNotContain("<--"),
+				Contains("CI commit 02").DoesNotContain("<--"),
+				Contains("CI commit 01").Contains("<-- good"),
+			).
+			// now checkout commit 08 manually
+			NavigateToLine(Contains("CI commit 08")).
+			Press(keys.Commits.CheckoutCommit).
+			Tap(func() {
+				t.ExpectPopup().Menu().
+					Title(Contains("Checkout branch or commit")).
+					Select(MatchesRegexp("Checkout commit .* as detached head")).
+					Confirm()
+			})
+
+		// after checkout, go back to commits panel and verify the current
+		// marker moved to commit 08
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("CI commit 10").Contains("<-- bad"),
+				Contains("CI commit 09").DoesNotContain("<--"),
+				Contains("CI commit 08").Contains("<-- current"),
+				Contains("CI commit 07").DoesNotContain("<--"),
+				Contains("CI commit 06").DoesNotContain("<--"),
+				Contains("CI commit 05").DoesNotContain("<--"),
+				Contains("CI commit 04").DoesNotContain("<--"),
+				Contains("CI commit 03").DoesNotContain("<--"),
+				Contains("CI commit 02").DoesNotContain("<--"),
+				Contains("CI commit 01").Contains("<-- good"),
+			).
+			// mark the manually checked-out commit as good via bisect menu
+			NavigateToLine(Contains("CI commit 08")).
+			Press(keys.Commits.ViewBisectOptions).
+			Tap(func() {
+				// the bisect menu should show the HEAD commit (08) as current
+				t.ExpectPopup().Menu().Title(Equals("Bisect")).
+					Select(MatchesRegexp(`Mark .* as good`)).Confirm()
+			}).
+			// after marking 08 as good, bisect narrows the range
+			SelectedLine(Contains("<-- current"))
+	},
+})

pkg/integration/tests/test_list.go

@@ -36,6 +36,7 @@ import (
 
 var tests = []*components.IntegrationTest{
 	bisect.Basic,
+	bisect.CheckoutDuringBisect,
 	bisect.ChooseTerms,
 	bisect.FromOtherBranch,
 	bisect.Skip,