project: Show detached head commit SHA in branch pickers (#29007)

When Git is in a detached HEAD state, the branch is `None`, and we can't
get any meaningful information from it. This PR adds a `head_commit`
field to the snapshot, which is always populated with the HEAD details,
even when the branch is `None`.

This also pave path to fix:
https://github.com/zed-industries/zed/issues/28736

git panel branch picker (before, after):
<img width="197" alt="image"
src="https://github.com/user-attachments/assets/0b6abbba-2988-4890-a708-bcd8aad84f26"
/> <img width="198" alt="image"
src="https://github.com/user-attachments/assets/4b08b1a8-5e79-4aa3-a44e-932249602c18"
/>

title bar branch picker (before, after):
<img width="183" alt="image"
src="https://github.com/user-attachments/assets/d94357f8-a4da-4d60-8ddd-fdd978b99fdf"
/> <img width="228" alt="image"
src="https://github.com/user-attachments/assets/d20824a1-9279-44d6-afd1-bf9319fc50e4"
/>

Release Notes:

- Added head commit SHA information to the Git branch picker in the
title bar and Git panel.

crates/collab/migrations.sqlite/20221109000000_test_schema.sql

@@ -117,6 +117,7 @@ CREATE TABLE "project_repositories" (
     "is_deleted" BOOL NOT NULL,
     "current_merge_conflicts" VARCHAR,
     "branch_summary" VARCHAR,
+    "head_commit_details" VARCHAR,
     PRIMARY KEY (project_id, id)
 );
 

crates/collab/src/db/queries/projects.rs

@@ -348,9 +348,10 @@ impl Database {
                                         .unwrap(),
                                 )),
 
-                                // Old clients do not use abs path or entry ids.
+                                // Old clients do not use abs path, entry ids or head_commit_details.
                                 abs_path: ActiveValue::set(String::new()),
                                 entry_ids: ActiveValue::set("[]".into()),
+                                head_commit_details: ActiveValue::set(None),
                             }
                         }),
                     )
@@ -490,6 +491,12 @@ impl Database {
                         .as_ref()
                         .map(|summary| serde_json::to_string(summary).unwrap()),
                 ),
+                head_commit_details: ActiveValue::Set(
+                    update
+                        .head_commit_details
+                        .as_ref()
+                        .map(|details| serde_json::to_string(details).unwrap()),
+                ),
                 current_merge_conflicts: ActiveValue::Set(Some(
                     serde_json::to_string(&update.current_merge_conflicts).unwrap(),
                 )),
@@ -505,6 +512,7 @@ impl Database {
                     project_repository::Column::EntryIds,
                     project_repository::Column::AbsPath,
                     project_repository::Column::CurrentMergeConflicts,
+                    project_repository::Column::HeadCommitDetails,
                 ])
                 .to_owned(),
             )
@@ -928,6 +936,13 @@ impl Database {
                     .transpose()?
                     .unwrap_or_default();
 
+                let head_commit_details = db_repository_entry
+                    .head_commit_details
+                    .as_ref()
+                    .map(|head_commit_details| serde_json::from_str(&head_commit_details))
+                    .transpose()?
+                    .unwrap_or_default();
+
                 let entry_ids = serde_json::from_str(&db_repository_entry.entry_ids)
                     .context("failed to deserialize repository's entry ids")?;
 
@@ -954,6 +969,7 @@ impl Database {
                         removed_statuses: Vec::new(),
                         current_merge_conflicts,
                         branch_summary,
+                        head_commit_details,
                         scan_id: db_repository_entry.scan_id as u64,
                         is_last_update: true,
                     });

crates/collab/src/db/queries/rooms.rs

@@ -755,6 +755,13 @@ impl Database {
                         .transpose()?
                         .unwrap_or_default();
 
+                    let head_commit_details = db_repository
+                        .head_commit_details
+                        .as_ref()
+                        .map(|head_commit_details| serde_json::from_str(&head_commit_details))
+                        .transpose()?
+                        .unwrap_or_default();
+
                     let entry_ids = serde_json::from_str(&db_repository.entry_ids)
                         .context("failed to deserialize repository's entry ids")?;
 
@@ -778,6 +785,7 @@ impl Database {
                             removed_statuses,
                             current_merge_conflicts,
                             branch_summary,
+                            head_commit_details,
                             project_id: project_id.to_proto(),
                             id: db_repository.id as u64,
                             abs_path: db_repository.abs_path,

crates/collab/src/db/tables/project_repository.rs

@@ -18,6 +18,8 @@ pub struct Model {
     pub current_merge_conflicts: Option<String>,
     // A JSON object representing the current Branch values
     pub branch_summary: Option<String>,
+    // A JSON object representing the current Head commit values
+    pub head_commit_details: Option<String>,
 }
 
 #[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]