Respect the diff context size when showing a range diff

This applies to both the "sticky" range diff when diffing mode is on, and the
more temporary one when selecting a range of commits.

pkg/commands/git_commands/diff.go

@@ -29,6 +29,7 @@ func (self *DiffCommands) DiffCmdObj(diffArgs []string) oscommands.ICmdObj {
 			Arg("--submodule").
 			Arg(fmt.Sprintf("--color=%s", self.UserConfig().Git.Paging.ColorArg)).
 			ArgIf(ignoreWhitespace, "--ignore-all-space").
+			Arg(fmt.Sprintf("--unified=%d", self.AppState.DiffContextSize)).
 			Arg(diffArgs...).
 			Dir(self.repoPaths.worktreePath).
 			ToArgv(),