packaging/scripts: Fix shebang

[btriller]

Include script header after type specific scriptlet to ensure type specific shebang is used.

Fixes: 19ccbed ("Adjusted detection of systemd in package scriptlets to handle more valid states")

[cf-bottom]

Thank you for submitting a PR! Maybe @craigcomstock can review this?

[craigcomstock]

@btriller thanks for the contribution, can you describe where and how you saw this as a problem? Thanks!

[btriller]

@btriller thanks for the contribution, can you describe where and how you saw this as a problem? Thanks!

Debian Trixie/CFEngine Community 3.27.0

% wget -q https://cfengine-package-repos.s3.amazonaws.com/community_binaries/Community-3.27.0/agent_debian13_x86_64/cfengine-community_3.27.0-1.debian13_amd64.deb
% dpkg --control cfengine-community_3.27.0-1.debian13_amd64.deb
% find DEBIAN -type f -perm /111 | xargs head -1
==> DEBIAN/preinst <==
USE_SYSTEMD=0

==> DEBIAN/postrm <==
USE_SYSTEMD=0

==> DEBIAN/prerm <==
USE_SYSTEMD=0

==> DEBIAN/postinst <==
USE_SYSTEMD=0

[btriller]

I didn't dig deeper but we have some hosts that didn't have cfengine3 service enabled after fresh installation.

[btriller]

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=622094
It seems that dpkg handles shebang in line 20 by accident in just running postinst script with system's default shell.

/tmp/cfe-install.strace.1674730:execve("/var/lib/dpkg/info/cfengine-community.postinst", ["/var/lib/dpkg/info/cfengine-community.postinst", "configure", "3.27.0-1.debian13"], 0x55b2b4fa5a80 /* 27 vars */) = -1 ENOEXEC (Exec format error)
/tmp/cfe-install.strace.1674730:execve("/bin/sh", ["/bin/sh", "/var/lib/dpkg/info/cfengine-community.postinst", "configure", "3.27.0-1.debian13"], 0x55b2b4fa5a80 /* 27 vars */) = 0
/tmp/cfe-install.strace.1674730:openat(AT_FDCWD, "/var/lib/dpkg/info/cfengine-community.postinst", O_RDONLY) = 3
/tmp/cfe-install.strace.1674730:read(10, "USE_SYSTEMD=0\n_use_systemd=$(command -v systemctl 2>&1 >/dev/null && systemctl is-system-running)\ncase \"$_use_systemd\" in\n  offline|unknown)\n    USE_SYSTEMD=0\n    ;;\n  \"\")\n    USE_SYSTEMD=0\n    ;;\n  *)\n    USE_SYSTEMD=1\n    ;;\nesac\n\nuse_systemd()\n{\n  test $USE_SYSTEMD = 1\n}\n\n#!/bin/sh\n\nPREFIX=/var/cfengine\n\npackage_type()\n{\n  echo deb\n}\n\nos_type()\n{\n  echo debian\n}\n\nrc_d_path()\n{\n  echo \"/etc\"\n}\n\nplatform_service()\n{\n  if use_systemd; then\n    /bin/systemctl \"$2\" \"$1\".service\n  else\n    /etc/init.d/\"$1\" \"$2\"\n  fi\n}\n\nIS_UPGRADE=0\n\ncase \"$1\" in\n  upgrade)\n    IS_UPGRADE=1\n    ;;\n  install|remove|purge)\n    IS_UPGRADE=0\n    ;;\n  configure)\n    # Actually not guaranteed to be correct.\n    IS_UPGRADE=0\n    ;;\n  *)\n    # Various error handling on debian. We ignore it for now.\n    exit 0\n    ;;\nesac\n\nnative_is_upgrade()\n{\n  test $IS_UPGRADE = 1\n}\nset -e\nPKG_TYPE=deb\nSCRIPT_TYPE=postinstall\nPROJECT_TYPE=cfengine-community\nBUILT_ON_OS=debian\nBUILT_ON_OS_VERSION=13\n# postgresql docs, https://www.postgresql.org/docs/cur"..., 8192) = 8192