A \score-lines markup list command for multi-lines embedded scores

A \score-lines markup list command for multi-lines embedded scores

Originally requested as issue 1334.

Like the \score markup, \score-lines is not called through the normal
markup list command mechanisms as it would require something awkward
along the lines of

\score-lines ##{ \score { ... } #}

to get this through.  Instead, a reserved word \score-lines in the
parser will manually call the command with an embedded score, leading
to just

\score-lines { ... }

This is somewhat clumsy in several ways: it requires an additional
reserved identifier (no other reserved identifier contains a dash),
and it means that a score may occur in a file without an explicit
enclosing \score command.

Nevertheless, the previous semantics implemented as issue 1334 were
not tenable: particularly after issue 3270 had been passed, it was
close to impossible for the average user to come up with a way of
getting an actual markup list from a score.

Note that there are as of yet no user-level commands spacing a markup
list in a way similar to the spacing inside of a \score markup.

[lemzwerg, 2013-11-03 08:56:47]

https://codereview.appspot.com/21280043/diff/1/lily/lily-lexer.cc
File lily/lily-lexer.cc (right):

https://codereview.appspot.com/21280043/diff/1/lily/lily-lexer.cc#newcode79
lily/lily-lexer.cc:79: {"score-lines", SCORELINES},
If the dash in `score-lines' is problematic (and I agree it would be better to
avoid it), why not change the keyword?  It has been introduced in a development
version, so I see no problems with that.  `scorelines' would be OK with me, for
example.  Or maybe `scorelist', since we already have `markuplist'.

[dak, 2013-11-03 09:34:56]

https://codereview.appspot.com/21280043/diff/1/lily/lily-lexer.cc
File lily/lily-lexer.cc (right):

https://codereview.appspot.com/21280043/diff/1/lily/lily-lexer.cc#newcode79
lily/lily-lexer.cc:79: {"score-lines", SCORELINES},
On 2013/11/03 08:56:47, lemzwerg wrote:
> If the dash in `score-lines' is problematic (and I agree it would be better to
> avoid it),

It isn't problematic.  It just seems out of place enough to require a
double-take.

> why not change the keyword?  It has been introduced in a development
> version, so I see no problems with that.

It hasn't actually been introduced at all yet.  Formally, there is a
\score-lines markup function, but one would not have used it except
possibly from Scheme, just like formally there is a \score markup
function.

> `scorelines' would be OK with me, for
> example.  Or maybe `scorelist', since we already have `markuplist'.

That's different.  Inside of markup we still have \*-lines commands
everywhere (for better or worse).  \markuplist is used _outside_ of
markups for generating markup lists. \*-lines are used _inside_ of
markup for generating markup lists.

No, all this is perfectly consistent.  It is also unproblematic to use
this kind of reserved word since issue 2702.

One could require writing \score-lines \score but that seems
unsymmetric with writing \score elsewhere.

It feels clunky, but it's definitely understandable, logical and
workable.  Which is more than issue 1334 achieved.

[dak, 2013-11-08 14:16:26]

doc string, regtest, make it actually work