git blame: Display GitHub avatars in blame tooltips, if available (#10767)

Release Notes:

- Added GitHub avatars to tooltips that appear when hovering over a `git
blame` entry (either inline or in the blame gutter).

Demo:



https://github.com/zed-industries/zed/assets/1185253/295c5aee-3a4e-46aa-812d-495439d8840d

crates/git/src/hosting_provider.rs

@@ -0,0 +1,107 @@
+use core::fmt;
+use std::{ops::Range, sync::Arc};
+
+use anyhow::Result;
+use url::Url;
+use util::{github, http::HttpClient};
+
+use crate::Oid;
+
+#[derive(Clone, Debug, Hash)]
+pub enum HostingProvider {
+    Github,
+    Gitlab,
+    Gitee,
+    Bitbucket,
+    Sourcehut,
+    Codeberg,
+}
+
+impl HostingProvider {
+    pub(crate) fn base_url(&self) -> Url {
+        let base_url = match self {
+            Self::Github => "https://github.com",
+            Self::Gitlab => "https://gitlab.com",
+            Self::Gitee => "https://gitee.com",
+            Self::Bitbucket => "https://bitbucket.org",
+            Self::Sourcehut => "https://git.sr.ht",
+            Self::Codeberg => "https://codeberg.org",
+        };
+
+        Url::parse(&base_url).unwrap()
+    }
+
+    /// Returns the fragment portion of the URL for the selected lines in
+    /// the representation the [`GitHostingProvider`] expects.
+    pub(crate) fn line_fragment(&self, selection: &Range<u32>) -> String {
+        if selection.start == selection.end {
+            let line = selection.start + 1;
+
+            match self {
+                Self::Github | Self::Gitlab | Self::Gitee | Self::Sourcehut | Self::Codeberg => {
+                    format!("L{}", line)
+                }
+                Self::Bitbucket => format!("lines-{}", line),
+            }
+        } else {
+            let start_line = selection.start + 1;
+            let end_line = selection.end + 1;
+
+            match self {
+                Self::Github | Self::Codeberg => format!("L{}-L{}", start_line, end_line),
+                Self::Gitlab | Self::Gitee | Self::Sourcehut => {
+                    format!("L{}-{}", start_line, end_line)
+                }
+                Self::Bitbucket => format!("lines-{}:{}", start_line, end_line),
+            }
+        }
+    }
+
+    pub fn supports_avatars(&self) -> bool {
+        match self {
+            HostingProvider::Github => true,
+            _ => false,
+        }
+    }
+
+    pub async fn commit_author_avatar_url(
+        &self,
+        repo_owner: &str,
+        repo: &str,
+        commit: Oid,
+        client: Arc<dyn HttpClient>,
+    ) -> Result<Option<Url>> {
+        match self {
+            HostingProvider::Github => {
+                let commit = commit.to_string();
+
+                let author =
+                    github::fetch_github_commit_author(repo_owner, repo, &commit, &client).await?;
+
+                let url = if let Some(author) = author {
+                    let mut url = Url::parse(&author.avatar_url)?;
+                    url.set_query(Some("size=128"));
+                    Some(url)
+                } else {
+                    None
+                };
+                Ok(url)
+            }
+            _ => Ok(None),
+        }
+    }
+}
+
+impl fmt::Display for HostingProvider {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let name = match self {
+            HostingProvider::Github => "GitHub",
+            HostingProvider::Gitlab => "GitLab",
+            HostingProvider::Gitee => "Gitee",
+            HostingProvider::Bitbucket => "Bitbucket",
+            HostingProvider::Sourcehut => "Sourcehut",
+            HostingProvider::Codeberg => "Codeberg",
+        };
+        write!(f, "{}", name)
+    }
+}