Preparing for a fast by eating/drinking on Shabbos

Question

If the fast of Tisha B'av comes out on Sunday, is it a problem of preparing for after Shabbos on Shabbos to eat or drink more than one normally would on Shabbos?

If a fast were on Tuesday, and one wanted to begin increasing their hydration on Shabbos, would that be any better (since the link between the two is ostensibly less obvious)?

Answer 1

Sh'miras Shabas K'hilchasah 28:77 (my own translation):

When the ninth of Av comes out on Sunday, it's permissible to eat and drink more than usual at the third meal on Shabas, even if his intent is to ease the fast, but he should not say that he's eating for that purpose.