Remove language::markdown (#25136)

The language::markdown crate had been superceded by markdown::Mardown.

After #25117, the only two remaining use-cases were rendering git commit
messages (which are arguably not really markdown) and the signature help
(which is definitely not markdown).

Updated the former to use the new markdown component, and the latter to
do syntax highlighting manually.

Release Notes:

- Allow selecting the commit message in git commits

crates/git_ui/src/git_panel.rs

@@ -16,7 +16,7 @@ use git::{repository::RepoPath, status::FileStatus, Commit, ToggleStaged};
 use git::{DiscardTrackedChanges, StageAll, TrashUntrackedFiles, UnstageAll};
 use gpui::*;
 use itertools::Itertools;
-use language::{markdown, Buffer, File, ParsedMarkdown};
+use language::{Buffer, File};
 use menu::{Confirm, SecondaryConfirm, SelectFirst, SelectLast, SelectNext, SelectPrev};
 use multi_buffer::ExcerptInfo;
 use panel::{panel_editor_container, panel_editor_style, panel_filled_button, PanelHeader};
@@ -2380,31 +2380,14 @@ impl GitPanelMessageTooltip {
         window: &mut Window,
         cx: &mut App,
     ) -> Entity<Self> {
-        let workspace = git_panel.read(cx).workspace.clone();
         cx.new(|cx| {
             cx.spawn_in(window, |this, mut cx| async move {
-                let language_registry = workspace.update(&mut cx, |workspace, _cx| {
-                    workspace.app_state().languages.clone()
-                })?;
-
                 let details = git_panel
                     .update(&mut cx, |git_panel, cx| {
                         git_panel.load_commit_details(&sha, cx)
                     })?
                     .await?;
 
-                let mut parsed_message = ParsedMarkdown::default();
-                markdown::parse_markdown_block(
-                    &details.message,
-                    Some(&language_registry),
-                    None,
-                    &mut parsed_message.text,
-                    &mut parsed_message.highlights,
-                    &mut parsed_message.region_ranges,
-                    &mut parsed_message.regions,
-                )
-                .await;
-
                 let commit_details = editor::commit_tooltip::CommitDetails {
                     sha: details.sha.clone(),
                     committer_name: details.committer_name.clone(),
@@ -2412,19 +2395,13 @@ impl GitPanelMessageTooltip {
                     commit_time: OffsetDateTime::from_unix_timestamp(details.commit_timestamp)?,
                     message: Some(editor::commit_tooltip::ParsedCommitMessage {
                         message: details.message.clone(),
-                        parsed_message,
                         ..Default::default()
                     }),
                 };
 
                 this.update_in(&mut cx, |this: &mut GitPanelMessageTooltip, window, cx| {
-                    this.commit_tooltip = Some(cx.new(move |cx| {
-                        CommitTooltip::new(
-                            commit_details,
-                            panel_editor_style(true, window, cx),
-                            Some(workspace),
-                        )
-                    }));
+                    this.commit_tooltip =
+                        Some(cx.new(move |cx| CommitTooltip::new(commit_details, window, cx)));
                     cx.notify();
                 })
             })