Setting schema from command line in psql

I keep a large number of separate development projects in a single
database, each in its own schema. Whenever I wish to work on one of them
in psql, after running

  psql <dbname>

I then have to type

  SET search_path TO <schemaname> [, PUBLIC] ;

I would really like to be able to do this from the command line, so that
I can make a wrapper for it, something like 'openproject <pname>'.

I read through the manual and the closest thing I could find was --set,
but this handles psql environment variables, which do not, as far as I
can see, affect the search_path.

Ideally I would like something like this:

  psql --schema <schemaname>    <- pg_dump already supports this

Or, perhaps better:

  psql --before-starting-execute-this-command "SET search_path....

(or a similar more digestable syntax)

Have I missed something in the docs ?

Thanks,

Daniel