Add new integration tests folder "shell_commands"

The folder custom_commands contained tests for both custom commands (the ones
you configure in config.yml) and shell commands (the ones you execute at the ":"
prompt). I always found this confusing, so separate these into two different
folders.

pkg/integration/tests/shell_commands/history.go

@@ -0,0 +1,60 @@
+package shell_commands
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var History = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Test that the custom commands history is saved correctly",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupRepo:    func(shell *Shell) {},
+	SetupConfig:  func(cfg *config.AppConfig) {},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.GlobalPress(keys.Universal.ExecuteCustomCommand)
+		t.ExpectPopup().Prompt().
+			Title(Equals("Custom command:")).
+			Type("echo 1").
+			Confirm()
+
+		t.GlobalPress(keys.Universal.ExecuteCustomCommand)
+		t.ExpectPopup().Prompt().
+			Title(Equals("Custom command:")).
+			SuggestionLines(Contains("1")).
+			Type("echo 2").
+			Confirm()
+
+		t.GlobalPress(keys.Universal.ExecuteCustomCommand)
+		t.ExpectPopup().Prompt().
+			Title(Equals("Custom command:")).
+			SuggestionLines(
+				// "echo 2" was typed last, so it should come first
+				Contains("2"),
+				Contains("1"),
+			).
+			Type("echo 3").
+			Confirm()
+
+		t.GlobalPress(keys.Universal.ExecuteCustomCommand)
+		t.ExpectPopup().Prompt().
+			Title(Equals("Custom command:")).
+			SuggestionLines(
+				Contains("3"),
+				Contains("2"),
+				Contains("1"),
+			).
+			Type("echo 1").
+			Confirm()
+
+		// Executing a command again should move it to the front:
+		t.GlobalPress(keys.Universal.ExecuteCustomCommand)
+		t.ExpectPopup().Prompt().
+			Title(Equals("Custom command:")).
+			SuggestionLines(
+				Contains("1"),
+				Contains("3"),
+				Contains("2"),
+			)
+	},
+})