meta: use long crate names

To help with clarity and potential publishing of the crates, the full
`radicle-` prefix is used for the crate names.

Note that it wasn't chosen got `git-ref-format` and `git-trailers`
since they are truly general libraries (bar the feature flag for link
specific reference names).

Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>

radicle-git-ext/src/error.rs

@@ -0,0 +1,22 @@
+// 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 std::{fmt::Display, io};
+
+pub fn is_not_found_err(e: &git2::Error) -> bool {
+    e.code() == git2::ErrorCode::NotFound
+}
+
+pub fn is_exists_err(e: &git2::Error) -> bool {
+    e.code() == git2::ErrorCode::Exists
+}
+
+pub fn into_git_err<E: Display>(e: E) -> git2::Error {
+    git2::Error::from_str(&e.to_string())
+}
+
+pub fn into_io_err(e: git2::Error) -> io::Error {
+    io::Error::new(io::ErrorKind::Other, e)
+}