dev-vcs/jj: add USE flags to live ebuild

This adds a git2 USE flag (enabled by default) to
match the git2 feature flag added by upstream.

This also adds a gix-max-performance USE flag to
match an existing featre flag. Upstream recommends
this be enabled by packagers, but I've left it
disabled by default here, as it comes with both a
dependency on cmake (for an unfortunately-vendored
zlib-ng) and potential incompatibilties (since it
uses assembly versions of SHA1 code in gitoxide).

Signed-off-by: demize <demize@unstable.systems>

dev-vcs/jj/jj-9999.ebuild

@@ -17,13 +17,22 @@ LICENSE+="
 	Apache-2.0 BSD MIT MPL-2.0 Unicode-3.0 Unicode-DFS-2016 WTFPL-2
 "
 SLOT="0"
+IUSE="
+	+git2
+	gix-max-performance
+"
 
-BDEPEND="virtual/pkgconfig"
+BDEPEND="
+	virtual/pkgconfig
+	gix-max-performance? ( dev-build/cmake )
+"
 DEPEND="
-	>=dev-libs/libgit2-1.9.0:0/1.9
-	dev-libs/openssl:=
-	net-libs/libssh2:=
-	sys-libs/zlib
+	git2? (
+		>=dev-libs/libgit2-1.9.0:0/1.9
+		sys-libs/zlib
+		dev-libs/openssl:=
+		net-libs/libssh2:=
+	)
 "
 RDEPEND="
 	${DEPEND}
@@ -45,6 +54,16 @@ src_unpack() {
 	cargo_live_src_unpack
 }
 
+src_configure() {
+	local myfeatures=(
+		$(usev git2)
+		$(usev gix-max-performance)
+		watchman
+		git
+	)
+	cargo_src_configure --no-default-features
+}
+
 src_install() {
 	cargo_src_install --path cli
 }

dev-vcs/jj/metadata.xml

@@ -8,4 +8,10 @@
   <upstream>
     <remote-id type="github">jj-vcs/jj</remote-id>
   </upstream>
+  <use>
+    <flag name="git2">Enables transitory support for <pkg>dev-libs/libgit2</pkg>.</flag>
+    <flag name="gix-max-performance">
+      Enables the "max-performance" feature when building gitoxide, allowing gitoxide to achieve better performance at the cost of wider compatibility.
+    </flag>
+  </use>
 </pkgmetadata>