Add merge options menu

Replace merge-tool with merge options menu that allows resolving all
conflicts for selected files as ours, theirs, or union, while still
providing access to the merge tool.

pkg/integration/tests/conflicts/merge_file_current.go

@@ -0,0 +1,76 @@
+package conflicts
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+	"github.com/jesseduffield/lazygit/pkg/integration/tests/shared"
+)
+
+func testDataCurrent() (original, current, incoming, final string) {
+	original = `
+1
+2
+3
+4
+5
+6
+`
+	current = `
+1
+2
+3
+4
+5a
+6
+`
+	incoming = `
+1b
+2
+3
+4
+5b
+6
+`
+	final = `
+1b
+2
+3
+4
+5a
+6
+`
+	return original, current, incoming, final
+}
+
+var MergeFileCurrent = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Conflicting file can be resolved to 'ours' (current changes) version via merge-file",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		original, current, incoming, _ := testDataCurrent()
+		shared.CreateMergeConflictFileForMergeFileTests(shell, original, current, incoming)
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		_, _, _, expected := testDataCurrent()
+
+		t.Views().Files().
+			IsFocused().
+			Lines(
+				Contains("file").IsSelected(),
+			)
+
+		t.GlobalPress(keys.Files.OpenMergeOptions)
+
+		t.ExpectPopup().Menu().
+			Title(Equals("Resolve merge conflicts")).
+			Select(Contains("Use current changes")). // merge-file --ours
+			Confirm()
+
+		t.Common().ContinueOnConflictsResolved("merge")
+
+		t.Views().Files().IsEmpty()
+
+		t.FileSystem().FileContent("file", Equals(expected))
+	},
+})