fix(date): treat composite strftime specifiers as atomic

[Abusalah0]

Fixes #11657

Summary

GNU date treats composite strftime directives (such as %D, %F, %T, %r, %R, %c, %x, %X) as atomic units. Formatting modifiers should apply to the full rendered result, not propagate into inner sub-fields.

Previously, uutils expanded composite directives (e.g. %D → %m/%d/%y) and applied modifiers to each inner specifier, leading to incorrect output such as:
+%-D → 6/15/24

where GNU correctly produces:
+%-D → 06/15/24

Fix

The fix is implemented in src/date/format/format_modifiers.rs:

• Added composite directive detection to identify %D, %F, %T, %r, %R, %c, %x, %X
• Updated modifier handling logic to treat composite outputs as atomic values
• Prevented modifier propagation (e.g. -, 0, width adjustments) into expanded sub-fields
• Preserved width and padding behavior at the top level

Tests

Changes in tests/by-util/test_date.rs:

• Enabled the regression test provided in this issue
• Added additional coverage for composite directives
• Added a dedicated %+10D test to verify width and padding behavior

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/retry. tests/tail/retry is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/date/resolution (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tty/tty-eof (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tail/tail-n0f (passes in this run but fails in the 'main' branch)

[sylvestre]

The new matches! arm now lists 18 letters across many lines. Since every composite is also space-padded by default, you can express
that relationship directly:

  fn is_space_padded_specifier(specifier: &str) -> bool {
      is_atomic_composite_specifier(specifier)
          || matches!(
              specifier.chars().last(),
              Some('A' | 'a' | 'B' | 'b' | 'h' | 'Z' | 'p' | 'P' | 'e' | 'k' | 'l')
          )
  }

no ?

[Abusalah0]

Yes Thank you,, I Updated it as suggested.

[sylvestre]

There are no tests for, e.g.:

• %^c → SAT JUN 15 03:04:05 2024
• %#c → swap-cased composite
• %^D → no-op on 06/15/24 (still 06/15/24)

[Abusalah0]

I just added tests for these Cases.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tty/tty-eof (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/tail/tail-n0f is now passing!