FR: support environment variables in (favourite) queries

Commencez par localiser la gestion des requêtes favorites de litecli et le point d’entrée des commandes \f ; l’issue ne nomme aucun fichier source ni aucun test. Examinez comment les arguments $1/$2 existants sont substitués, puis déterminez si l’expansion de l’environnement s’applique uniquement aux requêtes favorites ou à toutes les requêtes. Le travail est considéré comme terminé lorsque la syntaxe convenue fonctionne avec les variantes de base de données illustrées sans casser les paramètres de requête existants.

I'd love to see support for using environment variables in favourite queries, or even in all queries.

The use case is that I have several very similar databases where favourite queries all need to take a parameter to indicate what 'variant' of the database I'm currently using, or I have to copy configuration files for each database file and alter one value in each query filter.

Say, the different values are 'foo' and 'bar', and I have to either do:

favquery1 = '''select ...
    from some_table
    where parameter='$1'
    and other_paramater='$2'
'''
favquery2 = '''select ...
    from some_other_table sot inner join a_third_table att on sot.id = att.sot_id
    where sot.parameter='$1'
    and att.column_name ='$2'
'''

and then run \f favquery1 foo 42 and \f favquery2 bar 45, or I copy the configuration file multiple times and hardcode the parameter in each.

If, instead, I could use environment variables (syntax suggestion, feel free to come up with better syntax, this is based on bash):

favquery1 = '''select ...
    from some_table
    where parameter='${PARAMETER}'
    and other_paramater='$1'
'''
favquery2 = '''select ...
    from some_other_table sot inner join a_third_table att on sot.id = att.sot_id
    where sot.parameter='${PARAMETER}'
    and att.column_name ='$1'
'''

and then start each litecli instance with a different environment variable and use the exact same favourites for each database:

$ PARAMETER=foo litecli foo_database.sqlite
foo_database.sqlite> \f favquery1 42

and

$ PARAMETER=bar litecli bar_database.sqlite
bar_database.sqlite> \f favquery1 42