gnu: Add rust-git2-0.16.

* gnu/packages/crates-io.scm (rust-git2-0.16): New variable.
(rust-git2-0.15): Inherit from rust-git2-0.16.

gnu/packages/crates-io.scm

@@ -24467,10 +24467,10 @@ dirty state into your program.")
      "This is an internal macro crate for git-version.")
     (license license:bsd-2)))
 
-(define-public rust-git2-0.15
+(define-public rust-git2-0.16
   (package
     (name "rust-git2")
-    (version "0.15.0")
+    (version "0.16.1")
     (source
      (origin
        (method url-fetch)
@@ -24478,8 +24478,7 @@ dirty state into your program.")
        (file-name
         (string-append name "-" version ".tar.gz"))
        (sha256
-        (base32
-         "1lf7yxgrbglx5qqvk033n44ymmrg72z271911jwix9d6lgjbx519"))))
+        (base32 "1k1aavsfhk0i9jycc9gb61w2jwy8w9dgkd7zkz295wwm566gdxyc"))))
     (build-system cargo-build-system)
     (arguments
      `(#:cargo-inputs
@@ -24508,6 +24507,40 @@ repositories.  This library is both threadsafe and memory safe and allows both
 reading and writing git repositories.")
     (license (list license:expat license:asl2.0))))
 
+(define-public rust-git2-0.15
+  (package
+    (inherit rust-git2-0.16)
+    (name "rust-git2")
+    (version "0.15.0")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (crate-uri "git2" version))
+       (file-name
+        (string-append name "-" version ".tar.gz"))
+       (sha256
+        (base32
+         "1lf7yxgrbglx5qqvk033n44ymmrg72z271911jwix9d6lgjbx519"))))
+    (arguments
+     `(#:cargo-inputs
+       (("rust-bitflags" ,rust-bitflags-1)
+        ("rust-libc" ,rust-libc-0.2)
+        ("rust-libgit2-sys" ,rust-libgit2-sys-0.14)
+        ("rust-log" ,rust-log-0.4)
+        ("rust-openssl-probe" ,rust-openssl-probe-0.1)
+        ("rust-openssl-sys" ,rust-openssl-sys-0.9)
+        ("rust-url" ,rust-url-2))
+       #:cargo-development-inputs
+       (("rust-paste" ,rust-paste-1)
+        ("rust-structopt" ,rust-structopt-0.3)
+        ("rust-tempfile" ,rust-tempfile-3)
+        ("rust-time" ,rust-time-0.1))))
+    (native-inputs
+     `(("pkg-config" ,pkg-config)
+       ("git" ,git-minimal)))           ;for a single test
+    (inputs
+     (list libgit2 libssh2 openssl zlib))))
+
 (define-public rust-git2-0.14
   (package
     (inherit rust-git2-0.15)