cargo: make sure to pin git2 as well

The git2 crate is tied to specific versions of libgit2-sys, so
when upstream updates it, it will break builds.

By pinning git2 as well as libgit2-sys, we can prevent this.

Fixes #17339.

srcpkgs/cargo/template

@@ -12,6 +12,7 @@ maintainer="Enno Boland <gottox@voidlinux.org>"
 license="MIT, Apache-2.0"
 homepage="https://crates.io/"
 _libgit2_ver=0.9.1
+_git2_ver=0.10.1
 distfiles="https://github.com/rust-lang/cargo/archive/${version}.tar.gz
  https://github.com/rust-lang/git2-rs/archive/libgit2-sys-${_libgit2_ver}.tar.gz"
 checksum="b0a6808a2eaa9b20ccaeedeb04f583ee34b33d289f4d0076044b9fc2b1f4c59d
@@ -113,6 +114,7 @@ do_build() {
 
 	# gotta pin out libgit2-sys at the version
 	$cargo update
+	$cargo update --package git2 --precise ${_git2_ver}
 	$cargo update --package libgit2-sys --precise ${_libgit2_ver}
 	$cargo build --release $(vopt_if static --features="all-static")
 }