libgit2: Add support for OpenSSH instead of libssh2

This commit changes the original `ssh` feature into two new ones:
`ssh-libssh2` and `ssh-openssh`. By default, the `ssh-libssh2` feature
is enabled for backwards compatibility.

To use OpenSSH instead, the following listing in `Cargo.toml` can be
used:

    git2-rs = { version = "...", default-features = false, features = ["https", "ssh-openssh"] }

Author: bnjmnt4n

Diff for: Cargo.toml

@@ -34,7 +34,9 @@ tempfile = "3.1.0"
 [features]
 unstable = []
 default = ["ssh", "https"]
-ssh = ["libgit2-sys/ssh"]
+ssh = ["ssh-libssh2"]
+ssh-libssh2 = ["libgit2-sys/ssh-libssh2"]
+ssh-openssh = ["libgit2-sys/ssh-openssh"]
 https = ["libgit2-sys/https", "openssl-sys", "openssl-probe"]
 vendored-libgit2 = ["libgit2-sys/vendored"]
 vendored-openssl = ["openssl-sys/vendored", "libgit2-sys/vendored-openssl"]

Diff for: libgit2-sys/Cargo.toml

@@ -33,7 +33,9 @@ cc = { version = "1.0.43", features = ['parallel'] }
 openssl-sys = { version = "0.9.45", optional = true }
 
 [features]
-ssh = ["libssh2-sys"]
+ssh = ["ssh-libssh2"]
+ssh-libssh2 = ["libssh2-sys"]
+ssh-openssh = []
 https = ["openssl-sys"]
 vendored = []
 vendored-openssl = ["openssl-sys/vendored"]

Diff for: libgit2-sys/build.rs

@@ -29,7 +29,8 @@ fn main() {
     );
 
     let https = env::var("CARGO_FEATURE_HTTPS").is_ok();
-    let ssh = env::var("CARGO_FEATURE_SSH").is_ok();
+    let ssh_libssh2 = env::var("CARGO_FEATURE_SSH_LIBSSH2").is_ok();
+    let ssh_openssh = env::var("CARGO_FEATURE_SSH_OPENSSH").is_ok();
     let vendored = env::var("CARGO_FEATURE_VENDORED").is_ok();
     let zlib_ng_compat = env::var("CARGO_FEATURE_ZLIB_NG_COMPAT").is_ok();
 
@@ -182,13 +183,18 @@ The build is now aborting. To disable, unset the variable or use `LIBGIT2_NO_VEN
         features.push_str("#define GIT_ARCH_64 1\n");
     }
 
-    if ssh {
+    if ssh_openssh || ssh_libssh2 {
         if let Some(path) = env::var_os("DEP_SSH2_INCLUDE") {
             cfg.include(path);
         }
         features.push_str("#define GIT_SSH 1\n");
-        features.push_str("#define GIT_SSH_LIBSSH2 1\n");
-        features.push_str("#define GIT_SSH_LIBSSH2_MEMORY_CREDENTIALS 1\n");
+        if ssh_openssh {
+            features.push_str("#define GIT_SSH_EXEC 1\n");
+        }
+        if ssh_libssh2 {
+            features.push_str("#define GIT_SSH_LIBSSH2 1\n");
+            features.push_str("#define GIT_SSH_LIBSSH2_MEMORY_CREDENTIALS 1\n");
+        }
     }
     if https {
         features.push_str("#define GIT_HTTPS 1\n");

Diff for: libgit2-sys/lib.rs

@@ -5,7 +5,7 @@
 extern crate libz_sys as libz;
 
 use libc::{c_char, c_int, c_uchar, c_uint, c_void, size_t};
-#[cfg(feature = "ssh")]
+#[cfg(feature = "ssh-libssh2")]
 use libssh2_sys as libssh2;
 use std::ffi::CStr;
 
@@ -4353,12 +4353,12 @@ pub fn openssl_init() {
 #[doc(hidden)]
 pub fn openssl_init() {}
 
-#[cfg(feature = "ssh")]
+#[cfg(feature = "ssh-libssh2")]
 fn ssh_init() {
     libssh2::init();
 }
 
-#[cfg(not(feature = "ssh"))]
+#[cfg(not(feature = "ssh-libssh2"))]
 fn ssh_init() {}
 
 #[doc(hidden)]

Diff for: src/cred.rs

@@ -671,7 +671,7 @@ echo password=$2
     }
 
     #[test]
-    #[cfg(feature = "ssh")]
+    #[cfg(feature = "ssh-libssh2")]
     fn ssh_key_from_memory() {
         let cred = Cred::ssh_key_from_memory(
             "test",

Diff for: systest/Cargo.toml

@@ -6,7 +6,7 @@ build = "build.rs"
 edition = "2018"
 
 [dependencies]
-libgit2-sys = { path = "../libgit2-sys", features = ['https', 'ssh'] }
+libgit2-sys = { path = "../libgit2-sys", features = ['https', 'ssh-libssh2'] }
 libc = "0.2"
 
 [build-dependencies]