Rename head text to indicate that it's not always going to be from head

Co-Authored-By: Mikayla Maki <mikayla@zed.dev>

crates/rpc/proto/zed.proto

@@ -110,7 +110,7 @@ message Envelope {
         Unfollow unfollow = 95;
         GetPrivateUserInfo get_private_user_info = 96;
         GetPrivateUserInfoResponse get_private_user_info_response = 97;
-        UpdateHeadText update_head_text = 98;
+        UpdateDiffBase update_diff_base = 98;
     }
 }
 
@@ -830,7 +830,7 @@ message BufferState {
     uint64 id = 1;
     optional File file = 2;
     string base_text = 3;
-    optional string head_text = 4;
+    optional string diff_base = 4;
     LineEnding line_ending = 5;
 }
 
@@ -1002,8 +1002,8 @@ message WorktreeMetadata {
     bool visible = 3;
 }
 
-message UpdateHeadText {
+message UpdateDiffBase {
     uint64 project_id = 1;
     uint64 buffer_id = 2;
-    optional string head_text = 3;
+    optional string diff_base = 3;
 }

crates/rpc/src/proto.rs

@@ -167,7 +167,7 @@ messages!(
     (UpdateProject, Foreground),
     (UpdateWorktree, Foreground),
     (UpdateWorktreeExtensions, Background),
-    (UpdateHeadText, Background),
+    (UpdateDiffBase, Background),
     (GetPrivateUserInfo, Foreground),
     (GetPrivateUserInfoResponse, Foreground),
 );
@@ -267,7 +267,7 @@ entity_messages!(
     UpdateProject,
     UpdateWorktree,
     UpdateWorktreeExtensions,
-    UpdateHeadText
+    UpdateDiffBase
 );
 
 entity_messages!(channel_id, ChannelMessageSent);