Add test for how the selection advances after staging lines

This is currently working correctly, but will break with the next commit; we'll
fix this again afterwards.

pkg/integration/tests/staging/select_next_line_after_staging_in_two_hunk_diff.go

@@ -0,0 +1,61 @@
+package staging
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+// Tests that after staging individual lines from a consecutive changes block,
+// the cursor advances to the correct next change. The file has two separate
+// hunks so that we can verify the cursor crosses hunk boundaries correctly.
+var SelectNextLineAfterStagingInTwoHunkDiff = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "After staging lines from a two-hunk diff, the cursor advances correctly",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig: func(config *config.AppConfig) {
+		config.GetUserConfig().Gui.UseHunkModeInStagingView = false
+	},
+	SetupRepo: func(shell *Shell) {
+		// Use 7 context lines between the two change blocks so that git creates
+		// two separate hunks.
+		shell.CreateFileAndAdd("file1", "1\n2\na\nb\nc\nd\ne\nf\ng\n3\n4\n")
+		shell.Commit("one")
+
+		shell.UpdateFile("file1", "1b\n2b\na\nb\nc\nd\ne\nf\ng\n3b\n4b\n")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Files().
+			IsFocused().
+			Lines(
+				Contains("file1").IsSelected(),
+			).
+			PressEnter()
+
+		t.Views().Staging().
+			IsFocused().
+			ContainsLines(
+				Contains("-1"),
+				Contains("-2"),
+				Contains("+1b"),
+				Contains("+2b"),
+				Contains(" a"),
+				Contains(" b"),
+				Contains(" c"),
+				Contains("@@"),
+				Contains(" e"),
+				Contains(" f"),
+				Contains(" g"),
+				Contains("-3"),
+				Contains("-4"),
+				Contains("+3b"),
+				Contains("+4b"),
+			).
+			NavigateToLine(Contains("-2")).
+			PressPrimaryAction().
+			SelectedLine(Contains("+1b")).
+			PressPrimaryAction().
+			SelectedLine(Contains("+2b")).
+			PressPrimaryAction().
+			SelectedLine(Contains("-3"))
+	},
+})

pkg/integration/tests/test_list.go

@@ -377,6 +377,7 @@ var tests = []*components.IntegrationTest{
 	staging.DiffContextChange,
 	staging.DiscardAllChanges,
 	staging.Search,
+	staging.SelectNextLineAfterStagingInTwoHunkDiff,
 	staging.SelectNextLineAfterStagingIsolatedAddedLine,
 	staging.StageHunks,
 	staging.StageLines,