Initial FreeBSD support with pkgng plugin

Add a basic pkgng plugin as a preparation to integrate etckeeper on
FreeBSD. Currently not enabled to build automatically.

To use on FreeBSD, install etckeeper manually and install the plugin
with:
 $ cd pkgng
 $ make
 $ make install

and add this line to /usr/local/etc/pkg.conf:
 PLUGINS [ etckeeper ]

list-installed.d/50list-installed

@@ -17,5 +17,7 @@ else
 		rpm -qa --qf "%|epoch?{%{epoch}}:{0}|:%{name}-%{version}-%{release}.%{arch}\n" | sort
 	elif [ "$LOWLEVEL_PACKAGE_MANAGER" = pacman ]; then
 		pacman -Q
+	elif [ "$LOWLEVEL_PACKAGE_MANAGER" = pkgng ]; then
+		pkg info -E "*"
 	fi
 fi

pkgng/Makefile

@@ -0,0 +1,17 @@
+.include <bsd.own.mk>
+
+PREFIX?=	/usr/local
+LIBDIR=		${PREFIX}/lib/pkg/
+SHLIB_DIR?=	${LIBDIR}/
+SHLIB_NAME?=	${PLUGIN_NAME}.so
+
+PLUGIN_NAME=	etckeeper
+SRCS=		etckeeper.c
+
+PKGFLAGS!=	pkgconf --cflags pkg
+CFLAGS+=	${PKGFLAGS}
+
+beforeinstall:
+	${INSTALL} -d ${LIBDIR}
+
+.include <bsd.lib.mk>

pkgng/etckeeper.c

@@ -0,0 +1,132 @@
+/*
+ * Copyright (c) 2015 William Johansson <radar@radhuset.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer
+ *    in this position and unchanged.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Based upon the pkg plugin zfssnap:
+ * Copyright (c) 2012 Marin Atanasov Nikolov <dnaeon@gmail.com>
+ */
+
+#include <stdio.h>
+#include <sys/wait.h>
+#include <err.h>
+#include <errno.h>
+#include <spawn.h>
+
+#include <pkg.h>
+#define PLUGIN_NAME "etckeeper"
+/* TODO: make configuration param? */
+#define ETCKEEPER_PATH "/usr/local/bin/etckeeper"
+
+extern char **environ;
+
+struct pkg_plugin *self;
+
+static int pre_install_hook(void *data, struct pkgdb *db);
+static int post_install_hook(void *data, struct pkgdb *db);
+
+int
+pkg_plugin_init(struct pkg_plugin *p)
+{
+	self = p;
+
+	pkg_plugin_set(p, PKG_PLUGIN_NAME, PLUGIN_NAME);
+	pkg_plugin_set(p, PKG_PLUGIN_DESC, "etckeeper plugin");
+	pkg_plugin_set(p, PKG_PLUGIN_VERSION, "1.0.0");
+
+	/* NOTE: upgrade/deinstall is regarded as install */
+
+	if (pkg_plugin_hook_register(p, PKG_PLUGIN_HOOK_PRE_INSTALL, &pre_install_hook) != EPKG_OK) {
+		pkg_plugin_error(self, "failed to hook into the library");
+		return (EPKG_FATAL);
+	}
+
+	if (pkg_plugin_hook_register(p, PKG_PLUGIN_HOOK_POST_INSTALL, &post_install_hook) != EPKG_OK) {
+		pkg_plugin_error(self, "failed to hook into the library");
+		return (EPKG_FATAL);
+	}
+
+	if (pkg_plugin_hook_register(p, PKG_PLUGIN_HOOK_PRE_DEINSTALL, &pre_install_hook) != EPKG_OK) {
+		pkg_plugin_error(self, "failed to hook into the library");
+		return (EPKG_FATAL);
+	}
+
+	if (pkg_plugin_hook_register(p, PKG_PLUGIN_HOOK_POST_DEINSTALL, &post_install_hook) != EPKG_OK) {
+		pkg_plugin_error(self, "failed to hook into the library");
+		return (EPKG_FATAL);
+	}
+
+	if (pkg_plugin_hook_register(p, PKG_PLUGIN_HOOK_PRE_UPGRADE, &pre_install_hook) != EPKG_OK) {
+		pkg_plugin_error(self, "failed to hook into the library");
+		return (EPKG_FATAL);
+	}
+
+	if (pkg_plugin_hook_register(p, PKG_PLUGIN_HOOK_POST_UPGRADE, &post_install_hook) != EPKG_OK) {
+		pkg_plugin_error(self, "failed to hook into the library");
+		return (EPKG_FATAL);
+	}
+
+	return (EPKG_OK);
+}
+
+static int
+call_etckeeper(char *arg)
+{
+	int error, pstat;
+	pid_t pid;
+	char *argv[] = {
+		"etckeeper",
+		arg,
+		NULL,
+	};
+
+	if ((error = posix_spawn(&pid, ETCKEEPER_PATH, NULL, NULL,
+		__DECONST(char **, argv), environ)) != 0) {
+		errno = error;
+		pkg_plugin_errno(self, "Failed to spawn process", arg);
+		return (EPKG_FATAL);
+	}
+	while (waitpid(pid, &pstat, 0) == -1) {
+		if (errno != EINTR)
+			return (EPKG_FATAL);
+	}
+
+	if ((error = WEXITSTATUS(pstat)) != 0) {
+		pkg_plugin_error(self, "etckeeper failed with exit code %d", error);
+		return (EPKG_FATAL);
+	}
+
+	return (EPKG_OK);
+}
+
+static int
+pre_install_hook(void *data, struct pkgdb *db)
+{
+	return call_etckeeper("pre-install");
+}
+
+static int
+post_install_hook(void *data, struct pkgdb *db)
+{
+	return call_etckeeper("post-install");
+}