Installation: Add Gentoo ebuild

This commit adds an ebuild for Gentoo. Version 9999 is building live
from current git, currently using kakra:integration because it has some
installation and build fixes important for Gentoo.

Signed-off-by: Kai Krakow <kai@kaishome.de>

README.md

@@ -330,10 +330,21 @@ Bees can be installed by following one these instructions:
 Arch package
 ------------
 
-Bees is availabe Arch Linux AUR. Install with:
+Bees is availabe in Arch Linux AUR. Install with:
 
 `$ pacaur -S bees-git`
 
+Gentoo ebuild
+-------------
+
+Bees is available as a Gentoo ebuild. Just copy `bees-9999.ebuild` from
+`contrib/gentoo` including the `files` subdirectory to your local
+overlay category `sys-fs`.
+
+You can copy the ebuild to match a Bees version number, and it will
+build that tagged version. It is partly supported since v0.5,
+previous versions won't work.
+
 Build from source
 -----------------
 

contrib/gentoo/bees-9999.ebuild

@@ -0,0 +1,42 @@
+# Copyright 1999-2018 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=6
+
+inherit git-r3 eutils multilib
+
+DESCRIPTION="Best-Effort Extent-Same, a btrfs dedup agent"
+HOMEPAGE="https://github.com/Zygo/bees"
+
+if [[ ${PV} == "9999" ]] ; then
+	EGIT_REPO_URI="https://github.com/kakra/bees.git"
+	EGIT_BRANCH="integration"
+else
+	IUSE=""
+
+	SRC_URI="https://github.com/Zygo/bees/archive/v${PV}.tar.gz -> bees-${PV}.tar.gz"
+fi
+
+PATCHES="
+	${FILESDIR}/v0.5-gentoo_build.patch
+"
+
+LICENSE="GPL-3"
+SLOT="0"
+KEYWORDS=""
+IUSE=""
+
+DEPEND="
+	>=sys-apps/util-linux-2.30.2
+	>=sys-devel/gcc-4.9
+	>=sys-fs/btrfs-progs-4.1
+"
+RDEPEND="${DEPEND}"
+
+DOCS="README.md COPYING"
+HTML_DOCS="README.html"
+
+src_prepare() {
+	default
+	echo LIBDIR=$(get_libdir) >>${S}/localconf
+}

contrib/gentoo/files/v0.5-gentoo_build.patch

@@ -0,0 +1,20 @@
+diff --git a/localconf b/localconf
+new file mode 100644
+index 0000000..7705cbb
+--- /dev/null
++++ b/localconf
+@@ -0,0 +1,2 @@
++PREFIX=/
++LIBEXEC_PREFIX=/usr/libexec
+diff --git a/makeflags b/makeflags
+index f5983cb..0348623 100644
+--- a/makeflags
++++ b/makeflags
+@@ -1,4 +1,3 @@
+-CCFLAGS  = -Wall -Wextra -Werror -O3 -march=native -I../include -ggdb -D_FILE_OFFSET_BITS=64
+-# CCFLAGS  = -Wall -Wextra -Werror -O0 -I../include -ggdb -fpic -D_FILE_OFFSET_BITS=64
+-CFLAGS   = $(CCFLAGS) -std=c99
+-CXXFLAGS = $(CCFLAGS) -std=c++11 -Wold-style-cast
++CCFLAGS  = -O3 -I../include -fpic -D_FILE_OFFSET_BITS=64
++CFLAGS   += $(CCFLAGS) -std=c99
++CXXFLAGS += $(CCFLAGS) -std=c++11 -Wold-style-cast