Add integration test for worktree option in git command

Author: john-mutuma

pkg/integration/tests/worktree/fast_forward_worktree_branch_should_not_pollute_current_worktree.go

@@ -0,0 +1,57 @@
+package worktree
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var FastForwardWorktreeBranchNoPolluteCurrentWorktree = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Fast-forward a linked worktree branch from another worktree",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		// both main and linked worktree will have changed to fast-forward
+		shell.NewBranch("mybranch")
+		shell.CreateFileAndAdd("README.md", "hello world")
+		shell.Commit("initial commit")
+		shell.EmptyCommit("two")
+		shell.EmptyCommit("three")
+		shell.NewBranch("newbranch")
+
+		shell.CloneIntoRemote("origin")
+		shell.SetBranchUpstream("mybranch", "origin/mybranch")
+		shell.SetBranchUpstream("newbranch", "origin/newbranch")
+
+		// remove the 'three' commit so that we have something to pull from the remote
+		shell.HardReset("HEAD^")
+		shell.Checkout("mybranch")
+		shell.HardReset("HEAD^")
+
+		shell.AddWorktreeCheckout("newbranch", "../linked-worktree")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Branches().
+			Focus().
+			Lines(
+				Contains("mybranch").Contains("↓1").IsSelected(),
+				Contains("newbranch (worktree)").Contains("↓1"),
+			).
+			Press(keys.Branches.FastForward).
+			Lines(
+				Contains("mybranch").Contains("✓").IsSelected(),
+				Contains("newbranch (worktree)").Contains("↓1"),
+			).
+			NavigateToLine(Contains("newbranch (worktree)")).
+			Press(keys.Branches.FastForward).
+			Lines(
+				Contains("mybranch").Contains("✓"),
+				Contains("newbranch (worktree)").Contains("✓").IsSelected(),
+			)
+
+		// check the current worktree that it has no lines in the File changes pane
+		t.Views().Files().
+			Focus().
+			LineCount(EqualsInt(0))
+	},
+})