Add a function to get an owner-repo pair from the Git repo remote

This will allow us to accept suggestion IDs alone, without a full URL,
like the following:

    $ git sugapply 459691747
    # or
    $ git sugapply --remote upstream 459691747
    # or
    $ git config github-suggestion.remote upstream
    $ git sugapply 459691747

We do this by extracting the pair from the remote URL.

2 files changed, 84 insertions, 0 deletions

diff --git a/github-suggestion-config/Cargo.toml b/github-suggestion-config/Cargo.toml
new file mode 100644
index 0000000..788d00d
--- /dev/null
+++ b/github-suggestion-config/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "github-suggestion-config"
+version = "0.0.1"
+edition = "2018"
+
+[dependencies]
+git2 = "0.13.8"
+thiserror = "1.0.20"
+url = "2.1.1"
diff --git a/github-suggestion-config/src/lib.rs b/github-suggestion-config/src/lib.rs
new file mode 100644
index 0000000..c0d97a2
--- /dev/null
+++ b/github-suggestion-config/src/lib.rs
@@ -0,0 +1,75 @@
+use std::str::FromStr;
+
+use git2::Repository;
+use thiserror::Error;
+use url;
+use url::Url;
+
+
+#[derive(Debug, Error)]
+pub enum Error {
+    #[error(transparent)]
+    Git(#[from] git2::Error),
+
+    #[error(transparent)]
+    OwnerRepo(#[from] OwnerRepoError),
+
+    #[error("Unable to find remote '{0}'")]
+    NoRemote(String),
+}
+
+#[derive(Debug, Error)]
+pub enum OwnerRepoError {
+    #[error("Unable to parse URL")]
+    Url(#[from] url::ParseError),
+
+    #[error("URL has no path")]
+    NoPath,
+
+    #[error("Unable to parse owner or repo")]
+    NoOwnerRepo,
+}
+
+
+#[derive(Debug)]
+pub struct OwnerRepo {
+    pub owner: String,
+    pub repo: String,
+}
+
+impl FromStr for OwnerRepo {
+    type Err = OwnerRepoError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let url = Url::parse(s)?;
+        let path = url.path_segments()
+            .ok_or(OwnerRepoError::NoPath)?
+            .collect::<Vec<_>>();
+
+        if path.len() < 2 {
+            return Err(OwnerRepoError::NoOwnerRepo);
+        }
+
+        Ok(OwnerRepo {
+            owner: path[0].to_owned(),
+            repo: path[1].to_owned(),
+        })
+    }
+}
+
+pub fn identifier_for_remote(
+    remote_name: Option<&str>,
+) -> Result<OwnerRepo, Error> {
+    let repo = Repository::open(".")?;
+
+    let remote_name = match remote_name {
+        Some(r) => r,
+        None => "origin",
+    };
+
+    let remote = repo.find_remote(remote_name)?;
+    let url = remote.url()
+        .ok_or_else(|| Error::NoRemote(remote_name.to_owned()))?;
+
+    Ok(url.parse()?)
+}