in-use but safely deletable alts

https://forum.travelmapping.net/index.php?topic=5293.msg29822#msg29822 An in-use AltRouteName can be safely deleted if everyone using it marks the same segments via either...

the canonical name

usai;AR;I-49;;Tex;Texarkana, AR;ar.i049tex;AR549,I-130FutTex

egrep -i '^[ $t]*AR[ $t]+AR549[ $t]' *
okroads.list:AR AR549 4 35

egrep -i '^[ $t]*AR[ $t]+I-49Tex[ $t]' okroads.list 
AR I-49Tex LA/AR 35

grep -i I-130FutTex *
codyg1985.list:AR I-130FutTex 29(549) 35(549)

egrep -i '^[ $t]*AR[ $t]+I-49Tex[ $t]'  codyg1985.list 
AR I-49Tex 4 AR/TX

or another concurrent route

usai;NY;I-99;;;;ny.i099;I-99FutCor,I-99FutMan

egrep -i '^[ $t]*NY[ $t]+I-99FutCor[ $t]' *
1995hoo.list:NY I-99FutCor SouHilRd I-86
ngrier.list:NY I-99FutCor I-86 SouHilRd
verumsolum.list:NY I-99FutCor SouHilRd I-86

egrep -i '^[ $t]*NY[ $t]+I-99FutMan[ $t]' *
ngrier.list:NY I-99FutMan PA/NY WatCreRd
verumsolum.list:NY I-99FutMan PA/NY WatCreRd

egrep -i '^[ $t]*NY[ $t]+US15[ $t]' 1995hoo.list ngrier.list verumsolum.list
1995hoo.list:NY US15 PA/NY I-86
ngrier.list:NY US15 PA/NY I-86
verumsolum.list:NY US15 PA/NY I-86

The same idea applies with AltLabels. The same segments can be marked by another .list line via...

the same point's primary label,
another point farther along the same route, or
another concurrent route.

Low priority!

Implementation details TBD. (Nota bene: beware hidden systems if they're ever implemented) For what this would do, implementation would be complicated enough that it's probably not worth the hassle. It could yield a small number of things to clean up, sure, but it's arguably only needed for cases like NC295 as in the forum topic above when we want to re-use a name for a new route. For the rare time this happens, we could just take it case-by-case and use shell commands to see who uses what as in the examples above.

TravelMapping / DataProcessing

in-use but safely deletable alts #543

Low priority!