radicle-git init

Port over all git relevant parts of the radicle-link repository[0].
The packages that are kept are:
* git-ext
* git-ref-format
* git-trailers
* link-git
* macros
* std-ext
* test -- only the portions that test the above

The development and testing scripts are also added for local and CI
testing.

[0]: https://github.com/radicle-dev/radicle-link/
Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>

test/it-helpers/src/git.rs

@@ -0,0 +1,27 @@
+// Copyright © 2019-2020 The Radicle Foundation <hello@radicle.foundation>
+//
+// This file is part of radicle-link, distributed under the GPLv3 with Radicle
+// Linking Exception. For full terms see the included LICENSE file.
+
+use git_ref_format::Qualified;
+
+#[tracing::instrument(skip(repo))]
+pub fn create_commit(
+    repo: &git2::Repository,
+    on_branch: Qualified,
+) -> Result<git2::Oid, git2::Error> {
+    let empty_tree = {
+        let mut index = repo.index()?;
+        let oid = index.write_tree()?;
+        repo.find_tree(oid).unwrap()
+    };
+    let author = git2::Signature::now("The Animal", "animal@muppets.com").unwrap();
+    repo.commit(
+        Some(on_branch.as_str()),
+        &author,
+        &author,
+        "Initial commit",
+        &empty_tree,
+        &[],
+    )
+}