bsdunzip: make it possible to pass filenames starting with dash

We now check for residual arguments after the second scan, so any filename protected by `--` is picked up.

Author: Artoria2e5

unzip/bsdunzip.1

@@ -201,3 +201,16 @@ It uses the
 .Xr archive 3
 library developed by
 .An Tim Kientzle Aq Mt kientzle@FreeBSD.org .
+.Sh CAVEATS
+The
+.Nm
+utility performs two scans of the command-line for arguments before
+and after the archive name, so as to maintain compatibility with
+Info-ZIP unzip.
+As a result, the POSIX
+.Ql --
+double-dash string used to separate options from arguments will need to
+be repeated.
+For example, to extract a "-a.jpg" from "-b.zip" with overwrite, one
+would need to invoke
+.Dl bsdunzip -o -- -a.jpg -- -b.zip 

unzip/bsdunzip.c

@@ -1114,6 +1114,10 @@ main(int argc, char *argv[])
 	for (int i = 0; i < argc; ++i)
 		debug("%s%c", argv[i], (i < argc - 1) ? ' ' : '\n');
 
+#ifdef __GLIBC__
+	/* Prevent GNU getopt(3) from rearranging options. */
+	setenv("POSIXLY_CORRECT", "");
+#endif
 	/*
 	 * Info-ZIP's unzip(1) expects certain options to come before the
 	 * zipfile name, and others to come after - though it does not
@@ -1144,6 +1148,10 @@ main(int argc, char *argv[])
 	nopts--; /* fake argv[0] */
 	nopts += getopts(argc - nopts, argv + nopts);
 
+	/* There may be residual arguments if we encountered -- */
+	while (nopts < argc)
+		add_pattern(&include, argv[nopts++]);
+
 	if (n_opt + o_opt + u_opt > 1)
 		errorx("-n, -o and -u are contradictory");