Add integration test for commit highlighting on focus

A better refactor would be to allow matchers to assert against either a string or a slice of cells, so that I could have
the same ergonomics that I have elsewhere, but this is a start.

pkg/integration/tests/commit/highlight.go

@@ -0,0 +1,37 @@
+package commit
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var Highlight = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Verify that the commit view highlights the correct lines",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig: func(config *config.AppConfig) {
+		config.GetUserConfig().Git.Log.ShowGraph = "always"
+		config.GetUserConfig().Gui.AuthorColors = map[string]string{
+			"CI": "red",
+		}
+	},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("one")
+		shell.EmptyCommit("two")
+		shell.EmptyCommit("three")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		highlightedColor := "#ffffff"
+
+		t.Views().Commits().
+			DoesNotContainColoredText(highlightedColor, "◯").
+			Focus().
+			ContainsColoredText(highlightedColor, "◯")
+
+		t.Views().Files().
+			Focus()
+
+		t.Views().Commits().
+			DoesNotContainColoredText(highlightedColor, "◯")
+	},
+})