Allow for time adjustments with +/-

I much prefer this solution to the old one. Parsing times was a mistake.

I wonder if rustc realizes that I only ever pass 5 or -5 as arguments to
that function and then creates two `time::Duration`s for 5 and -5
minutes respectively to avoid the allocations on each keypress.

Also, I had to satisfy the OCD meme by rounding all adjusted times to %5.
It would be too annoying to change a number without being able to always
set it to a “nice” number.

src/timesheet.rs

@@ -77,6 +77,16 @@ impl TimeSheet {
         self.times.iter().map(TimePoint::to_string).collect()
     }
 
+    /**
+     * Adjust the current time by `minutes` and round the result to a multiple of `minutes`.
+     * This is so I can adjust in steps of 5 but still get nice, even numbers in the output.
+     */
+    pub fn shift_current(&mut self, minutes: i64) {
+        let time = &mut self.times[self.selected].time;
+        let current_minute = time.minute() as i64;
+        *time += Duration::minutes(minutes - current_minute % minutes);
+    }
+
     fn current(&self) -> &TimePoint {
         &self.times[self.selected]
     }

src/tracc.rs

@@ -69,6 +69,8 @@ impl Tracc {
                     }
                     Key::Char('a') | Key::Char('A') => self.set_mode(Mode::Insert)?,
                     Key::Char(' ') if self.focus == Focus::Top => self.todos.toggle_current(),
+                    Key::Char('-') if self.focus == Focus::Bottom => self.times.shift_current(-5),
+                    Key::Char('+') if self.focus == Focus::Bottom => self.times.shift_current(5),
                     // dd
                     Key::Char('d') => {
                         if let Some(Ok(Key::Char('d'))) = inputs.next() {