Note in soft upgrade docs that legacy.sql needs to be rerun for each minor upgrade

[robe]

As noted by someone on IRC, if you upgrade PostGIS from 2.something to 2.1 and forget to rerun the legacy.sql script (only applies if you ran it in first place),

You may get:

Thing is, spatial queries still report this:

ERROR: could not access file "$libdir/postgis-2.0": No such file or directory

I've also seen the dreaded backend error caused by two versions of PostGIS running in same db with same set of GUCs fighting for each other. The other error (can't remember what it is), happens if postgis-2.0 is still present (then you have the unpleasant situation of 2 instances of PostGIS running)

I'm hoping in 2.2 that we can get rid of all references to $libdir in the legacy scripts, but fair there may be a couple we can't get rid of.

[robe]

this is really something that should be backported once fixed, but too lazy to do for 2.2

[robe]

In 16494:

note in docs about soft upgrade that legacy.sql must be rerun for each minor.
References #2960 for PostGIS 2.5.0 (trunk)

[robe]

In 16495:

note in docs about soft upgrade that legacy.sql must be rerun for each minor.
Closes #2960 for PostGIS 2.4.4