1.0: First version.
1.0a: Changed parameters for bypassing prechecks to allow bypassing
	the signify binary executable check first.
1.0b: Added another check on verify_gzip for require_public_key_file so
	it's not a no-op when skip_checks is used.
1.0c: Improved verify error handling so /bin/sh doesn't have to be unveiled
	and for consistency between verify and verify_gzip.
1.0d: Use signify-openbsd when running on Linux.
1.0e: Be less strict on key dir since OpenBSD 7.8 doesn't include it.
1.1: Cleanup: avoid shell, use chomp instead of chop, use randomly named temp
	files in gzip handling.
1.1a: Remove use of backticks with IPC::Open3 and no longer manually parse
	gzip header or depend on comment field order.
1.1b: Fix tempfile handling, broken gzip verification, and minor issues.
1.1c: Clean up error messages and exception handling in verify_gzip.
1.1d: Support macOS (Homebrew) location of signify and remove some but
	not all gzip header check redundancy.
1.1e: Properly initialize @ERROR array.
1.1f: Cosmetic changes, remove unnecessary & and ".
1.1g: Check for error on copy at and of sign_gzip.
1.2: Clean up orphaned tempfile paths, potential IPC::Open3 deadlock,
	unnecessary conditional on basename call, stop using bareword
	filehandles.
1.2a: Add get_gzip_signer.
1.3: Fix bugs and add named parameter form.
	Bugs: _verify_gzip_signature ignores SIGPIPE in the parent while
	streaming, so a tampered or wrong-key package no longer kills the
	caller; treats signify killed by a signal (or a failed waitpid) as
	not verified instead of verified; the forked child reports
	exec/dup failures and leaves with POSIX::_exit instead of die, so
	the caller's END blocks and code never run in the child; rejects a
	gzip header with no usable key name. sign_gzip writes the signed
	output to a temp file beside the original and renames it into
	place (keeping the original's mode and owner), so a failure can no
	longer truncate the original; it no longer uses $temp_dir. sign
	and sign_gzip check signify's exit status and ignore SIGPIPE while
	sending the passphrase. Fixed literal "\n" in two error messages
	and "directory dir" in sign. Corrected the pledge/unveil notes and
	the required Perl version. Added a named-argument form to sign,
	verify, sign_gzip and verify_gzip; the positional form still works
	and is to be removed once all callers (install.pl, distribute.pl,
	reportnew, sigtree.pl) use the named form.
1.4: Fix passphrase bug: write with syswrite instead of print.
