Disregard master commits when finding base commit for fixup

If exactly one candidate from inside the current branch is found, we return that
one even if there are also hunks belonging to master commits; we disregard those
in this case.

pkg/integration/tests/commit/find_base_commit_for_fixup_disregard_main_branch.go

@@ -35,7 +35,6 @@ var FindBaseCommitForFixupDisregardMainBranch = NewIntegrationTest(NewIntegratio
 			Focus().
 			Press(keys.Files.FindBaseCommitForFixup)
 
-		/* EXPECTED:
 		t.Views().Commits().
 			IsFocused().
 			Lines(
@@ -44,13 +43,5 @@ var FindBaseCommitForFixupDisregardMainBranch = NewIntegrationTest(NewIntegratio
 				Contains("2nd commit"),
 				Contains("1st commit"),
 			)
-		*/
-
-		// ACTUAL:
-		t.ExpectPopup().Alert().Title(Equals("Error")).Content(
-			Contains("Multiple base commits found.").
-				Contains("2nd commit").
-				Contains("3rd commit"),
-		).Confirm()
 	},
 })