mini glissando line for portamento?

[Evan Laforge]

I'm accustomed to using a short glissando line to indicate a rapid
glissando between notes.  What I mean is that given 'c1 \glissando |
d1', the implication is that the player spends the whole duration
slowly moving.  But if I want something like 'c2~ c4~ c8 c8 \glissando
| d1', then I omit the tied notes and just write a short glissando
line as if it were coming from that last c8.  First of all, is this a
reasonable way to notate short portamento-like slides?  Secondly,
assuming it is, while I imagine I could insert a bunch of hidden rests
in another voice to attach the \glissando, surely there's an easier
way to change the glissando start point to the next note minus some
constant distance?  I can tweak Glissando.bound-details.left.padding,
but that doesn't change the slope of the line.

Thanks!