Add ability to copy a permalink to a line (#7119)

This PR adds the ability to copy the permalink to a line from within
Zed.

This functionality is available through the `editor: copy permalink to
line` action in the command palette:

<img width="589" alt="Screenshot 2024-01-30 at 7 07 46 PM"
src="https://github.com/zed-industries/zed/assets/1486634/332282cb-211f-4f16-9eb1-415bcfee9b7b">

Executing this action will create a permalink to the currently selected
line(s) and copy it to the clipboard.

Here is an example line:

```
56c80e8011/src/lib.rs (L25)
```

Currently, both GitHub and GitLab are supported.

### Notes and known limitations

- In order to determine where to permalink to, we read the URL of the
`origin` remote in Git. This feature will not work if the `origin`
remote is not present.
- Attempting to permalink to a ref that is not pushed to the origin will
result in the link 404ing.
- Attempting to permalink when Git is in a dirty state may not generate
the right link.
- For instance, modifying a file (e.g., adding new lines) and grabbing a
permalink to it will result in incorrect line numbers.

Release Notes:

- Added the ability to copy a permalink to a line
([#6777](https://github.com/zed-industries/zed/issues/6777)).
- Available via the `editor: copy permalink to line` action in the
command palette.

crates/fs/src/repository.rs

@@ -26,8 +26,14 @@ pub struct Branch {
 pub trait GitRepository: Send {
     fn reload_index(&self);
     fn load_index_text(&self, relative_file_path: &Path) -> Option<String>;
+
+    /// Returns the URL of the remote with the given name.
+    fn remote_url(&self, name: &str) -> Option<String>;
     fn branch_name(&self) -> Option<String>;
 
+    /// Returns the SHA of the current HEAD.
+    fn head_sha(&self) -> Option<String>;
+
     /// Get the statuses of all of the files in the index that start with the given
     /// path and have changes with respect to the HEAD commit. This is fast because
     /// the index stores hashes of trees, so that unchanged directories can be skipped.
@@ -88,12 +94,22 @@ impl GitRepository for LibGitRepository {
         None
     }
 
+    fn remote_url(&self, name: &str) -> Option<String> {
+        let remote = self.find_remote(name).ok()?;
+        remote.url().map(|url| url.to_string())
+    }
+
     fn branch_name(&self) -> Option<String> {
         let head = self.head().log_err()?;
         let branch = String::from_utf8_lossy(head.shorthand_bytes());
         Some(branch.to_string())
     }
 
+    fn head_sha(&self) -> Option<String> {
+        let head = self.head().ok()?;
+        head.target().map(|oid| oid.to_string())
+    }
+
     fn staged_statuses(&self, path_prefix: &Path) -> TreeMap<RepoPath, GitFileStatus> {
         let mut map = TreeMap::default();
 
@@ -255,11 +271,19 @@ impl GitRepository for FakeGitRepository {
         state.index_contents.get(path).cloned()
     }
 
+    fn remote_url(&self, _name: &str) -> Option<String> {
+        None
+    }
+
     fn branch_name(&self) -> Option<String> {
         let state = self.state.lock();
         state.branch_name.clone()
     }
 
+    fn head_sha(&self) -> Option<String> {
+        None
+    }
+
     fn staged_statuses(&self, path_prefix: &Path) -> TreeMap<RepoPath, GitFileStatus> {
         let mut map = TreeMap::default();
         let state = self.state.lock();