Add integration test for filtering the stashes list by file path

The test shows that it doesn't work, the list is empty both when filtering by
file and by folder.

I could have added test cases for these to the unit tests in
stash_loader_test.go instead, but I don't find tests that need to mock git's
output very valuable, so I opted for an integration test even though it takes
much longer to run.

pkg/integration/tests/stash/filter_by_path.go

@@ -0,0 +1,66 @@
+package stash
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var FilterByPath = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Filter the stash list by path",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("initial commit")
+		shell.CreateFileAndAdd("file1", "content")
+		shell.Stash("file1")
+		shell.CreateDir("subdir")
+		shell.CreateFileAndAdd("subdir/file2", "content")
+		shell.Stash("subdir/file2")
+		shell.CreateFileAndAdd("file1", "other content")
+		shell.Stash("file1 again")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		filterBy := func(path string) {
+			t.GlobalPress(keys.Universal.FilteringMenu)
+			t.ExpectPopup().Menu().
+				Title(Equals("Filtering")).
+				Select(Contains("Enter path to filter by")).
+				Confirm()
+
+			t.ExpectPopup().Prompt().
+				Title(Equals("Enter path:")).
+				Type(path).
+				Confirm()
+		}
+
+		t.Views().Stash().
+			Lines(
+				Contains("file1 again"),
+				Contains("subdir/file2"),
+				Contains("file1"),
+			)
+
+		filterBy("file1")
+
+		t.Views().Stash().
+			/* EXPECTED:
+			Lines(
+				Contains("file1 again"),
+				Contains("file1"),
+			)
+			ACTUAL: */
+			IsEmpty()
+
+		t.GlobalPress(keys.Universal.Return)
+		filterBy("subdir")
+
+		t.Views().Stash().
+			/* EXPECTED:
+			Lines(
+				Contains("subdir/file2"),
+			)
+			ACTUAL: */
+			IsEmpty()
+	},
+})

pkg/integration/tests/test_list.go

@@ -352,6 +352,7 @@ var tests = []*components.IntegrationTest{
 	stash.CreateBranch,
 	stash.Drop,
 	stash.DropMultiple,
+	stash.FilterByPath,
 	stash.Pop,
 	stash.PreventDiscardingFileChanges,
 	stash.Rename,