refactor(preg): report unmatched groups as null throughout

The shim carried two reporting modes for the preg_* $matches maps: PHP's
default (trailing unmatched groups dropped, interior ones ""), and the
PREG_UNMATCHED_AS_NULL form, picked by calling a *_unmatched_as_null()
variant. The regex crate hands out Option<Match>, which maps onto the
null form directly, and no caller distinguished a dropped group from a
null one -- preg_match() and preg_match_all2() already reported nulls
unconditionally. Keep only the null form; the shim API no longer mirrors
PHP's flag set, which is intended.

Preg::is_match_with_indexed_captures() modelled PHP's "unset" as a
truncated Vec<String>, and now returns Vec<Option<String>>. That is what
Composer actually does: Preg::isMatch() always sets
PREG_UNMATCHED_AS_NULL, and its callers test groups with `!== null`.

preg_match_all(), preg_match_all_set_order() and
preg_split_delim_capture() still hand back Vec<String> and keep the ""
form.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/crates/shirabe/src/package/version/version_guesser.rs b/crates/shirabe/src/package/version/version_guesser.rs
index 4f46919e..4b5187f2 100644
--- a/crates/shirabe/src/package/version/version_guesser.rs
+++ b/crates/shirabe/src/package/version/version_guesser.rs
@@ -704,9 +704,9 @@ impl VersionGuesser {
             );
 
             if let Some(matches) = Preg::is_match_with_indexed_captures(&url_pattern, &output) {
-                let m1 = matches.get(1).cloned().unwrap_or_default();
-                let m2 = matches.get(2).cloned();
-                let m3 = matches.get(3).cloned();
+                let m1 = matches[1].clone().unwrap_or_default();
+                let m2 = matches[2].clone();
+                let m3 = matches[3].clone();
                 if let Some(m2) = m2.as_ref()
                     && let Some(m3) = m3.as_ref()
                     && (branches_path == *m2 || tags_path == *m2)