Add command to find base commit for creating a fixup

pkg/integration/tests/commit/find_base_commit_for_fixup.go

@@ -0,0 +1,79 @@
+package commit
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var FindBaseCommitForFixup = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Finds the base commit to create a fixup for",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.NewBranch("mybranch").
+			EmptyCommit("1st commit").
+			CreateFileAndAdd("file1", "file1 content\n").
+			Commit("2nd commit").
+			CreateFileAndAdd("file2", "file2 content\n").
+			Commit("3rd commit").
+			UpdateFile("file1", "file1 changed content").
+			UpdateFile("file2", "file2 changed content")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Lines(
+				Contains("3rd commit"),
+				Contains("2nd commit"),
+				Contains("1st commit"),
+			)
+
+		// Two changes from different commits: this fails
+		t.Views().Files().
+			Focus().
+			Press(keys.Files.FindBaseCommitForFixup)
+
+		t.ExpectPopup().Alert().
+			Title(Equals("Error")).
+			Content(
+				Contains("Multiple base commits found").
+					Contains("2nd commit").
+					Contains("3rd commit"),
+			).
+			Confirm()
+
+		// Stage only one of the files: this succeeds
+		t.Views().Files().
+			IsFocused().
+			NavigateToLine(Contains("file1")).
+			PressPrimaryAction().
+			Press(keys.Files.FindBaseCommitForFixup)
+
+		t.Views().Commits().
+			IsFocused().
+			Lines(
+				Contains("3rd commit"),
+				Contains("2nd commit").IsSelected(),
+				Contains("1st commit"),
+			).
+			Press(keys.Commits.AmendToCommit)
+
+		t.ExpectPopup().Confirmation().
+			Title(Equals("Amend commit")).
+			Content(Contains("Are you sure you want to amend this commit with your staged files?")).
+			Confirm()
+
+		// Now only the other file is modified (and unstaged); this works now
+		t.Views().Files().
+			Focus().
+			Press(keys.Files.FindBaseCommitForFixup)
+
+		t.Views().Commits().
+			IsFocused().
+			Lines(
+				Contains("3rd commit").IsSelected(),
+				Contains("2nd commit"),
+				Contains("1st commit"),
+			)
+	},
+})