Add pull requests to git blame tooltip (#10784)

Release Notes:

- Added links to GitHub pull requests to the git blame tooltips, if they
are available.

Screenshot:

(Yes, the icon will be resized! cc @iamnbutler)

![screenshot-2024-04-19-18 31
13@2x](https://github.com/zed-industries/zed/assets/1185253/774af0b3-f587-4acc-aa1e-1846c2bec127)

crates/git/Cargo.toml

@@ -25,6 +25,7 @@ time.workspace = true
 url.workspace = true
 util.workspace = true
 serde.workspace = true
+regex.workspace = true
 rope.workspace = true
 parking_lot.workspace = true
 windows.workspace = true

crates/git/src/git.rs

@@ -12,6 +12,7 @@ pub mod commit;
 pub mod diff;
 pub mod hosting_provider;
 pub mod permalink;
+pub mod pull_request;
 pub mod repository;
 
 lazy_static! {

crates/git/src/pull_request.rs

@@ -0,0 +1,83 @@
+use lazy_static::lazy_static;
+use url::Url;
+
+use crate::{hosting_provider::HostingProvider, permalink::ParsedGitRemote};
+
+lazy_static! {
+    static ref GITHUB_PULL_REQUEST_NUMBER: regex::Regex =
+        regex::Regex::new(r"\(#(\d+)\)$").unwrap();
+}
+
+#[derive(Clone, Debug)]
+pub struct PullRequest {
+    pub number: u32,
+    pub url: Url,
+}
+
+pub fn extract_pull_request(remote: &ParsedGitRemote, message: &str) -> Option<PullRequest> {
+    match remote.provider {
+        HostingProvider::Github => {
+            let line = message.lines().next()?;
+            let capture = GITHUB_PULL_REQUEST_NUMBER.captures(line)?;
+            let number = capture.get(1)?.as_str().parse::<u32>().ok()?;
+
+            let mut url = remote.provider.base_url();
+            let path = format!("/{}/{}/pull/{}", remote.owner, remote.repo, number);
+            url.set_path(&path);
+
+            Some(PullRequest { number, url })
+        }
+        _ => None,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use unindent::Unindent;
+
+    use crate::{
+        hosting_provider::HostingProvider, permalink::ParsedGitRemote,
+        pull_request::extract_pull_request,
+    };
+
+    #[test]
+    fn test_github_pull_requests() {
+        let remote = ParsedGitRemote {
+            provider: HostingProvider::Github,
+            owner: "zed-industries",
+            repo: "zed",
+        };
+
+        let message = "This does not contain a pull request";
+        assert!(extract_pull_request(&remote, message).is_none());
+
+        // Pull request number at end of first line
+        let message = r#"
+            project panel: do not expand collapsed worktrees on "collapse all entries" (#10687)
+
+            Fixes #10597
+
+            Release Notes:
+
+            - Fixed "project panel: collapse all entries" expanding collapsed worktrees.
+            "#
+        .unindent();
+
+        assert_eq!(
+            extract_pull_request(&remote, &message)
+                .unwrap()
+                .url
+                .as_str(),
+            "https://github.com/zed-industries/zed/pull/10687"
+        );
+
+        // Pull request number in middle of line, which we want to ignore
+        let message = r#"
+            Follow-up to #10687 to fix problems
+
+            See the original PR, this is a fix.
+            "#
+        .unindent();
+        assert!(extract_pull_request(&remote, &message).is_none());
+    }
+}