feat(php-src): add a BSD-licensed crate for php-src derived code

The audit in .ken/php-shim-copying.md judged 14 functions in
shirabe-php-shim (plus php_wordwrap in shirabe-external-packages) to be
line-by-line transcriptions or structural imitations of php-src. PHP's
relicensing to 3-clause BSD makes keeping them legal, but the boundary
between BSD-derived and MIT code was invisible in the source tree.

Moving them into their own crate puts the license into the build
metadata (so NOTICE generation follows the binary), makes a reverse
dependency a compile error, and encodes the origin in the module path,
which mirrors php-src's ext tree. Each function records its origin in a
fixed-format doc comment, and a new php_src_derivation_boundary linter
fails if `php-src` appears in any Rust source outside the crate.

Public paths under shirabe_php_shim:: are unchanged: functions that are
themselves derived are re-exported with `pub use`, and the wrappers that
only validate arguments stay on the MIT side.

This also resolves the duplicate wordwrap implementation.
shirabe_php_shim::wordwrap was todo!(), so SymfonyStyle::block panicked,
while shirabe-external-packages carried its own copy. Both now go
through the single port, verified against real PHP on 13 cases covering
multi-character breaks and cut.

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

1 files changed, 40 insertions, 0 deletions

diff --git a/crates/shirabe-php-src/src/standard/exec.rs b/crates/shirabe-php-src/src/standard/exec.rs
new file mode 100644
index 00000000..80ab26ae
--- /dev/null
+++ b/crates/shirabe-php-src/src/standard/exec.rs
@@ -0,0 +1,40 @@
+/// php-src: ext/standard/exec.c `php_escape_shell_cmd` (PHP 8.5.2)
+///
+/// Unix branch only. Shell metacharacters are backslash-escaped; quote characters are escaped
+/// only when unpaired, paired quotes being left intact. The multibyte skip (`php_mblen`), the
+/// command length check and the Windows branch are not ported.
+pub fn escapeshellcmd(command: &str) -> String {
+    let bytes = command.as_bytes();
+    let len = bytes.len();
+    let mut out: Vec<u8> = Vec::with_capacity(len);
+    // Byte index of the matching closing quote while inside a paired quote run.
+    let mut paired: Option<usize> = None;
+    let mut x = 0;
+    while x < len {
+        let c = bytes[x];
+        match c {
+            b'"' | b'\'' => {
+                if paired.is_none() {
+                    if let Some(rel) = bytes[x + 1..].iter().position(|&b| b == c) {
+                        paired = Some(x + 1 + rel);
+                    } else {
+                        out.push(b'\\');
+                    }
+                } else if paired == Some(x) {
+                    paired = None;
+                } else {
+                    out.push(b'\\');
+                }
+                out.push(c);
+            }
+            b'#' | b'&' | b';' | b'`' | b'|' | b'*' | b'?' | b'~' | b'<' | b'>' | b'^' | b'('
+            | b')' | b'[' | b']' | b'{' | b'}' | b'$' | b'\\' | 0x0A | 0xFF => {
+                out.push(b'\\');
+                out.push(c);
+            }
+            _ => out.push(c),
+        }
+        x += 1;
+    }
+    String::from_utf8_lossy(&out).into_owned()
+}