jj git push: remove the NotFastForward error

Now that we always force push, it should not occur in practice.

cli/src/commands/git.rs

@@ -1015,13 +1015,11 @@ fn cmd_git_push(
     })
     .map_err(|err| match err {
         GitPushError::InternalGitError(err) => map_git_error(err),
-        GitPushError::NotFastForward | GitPushError::RefInUnexpectedLocation(_) => {
-            user_error_with_hint(
-                err.to_string(),
-                "Try fetching from the remote, then make the branch point to where you want it to \
-                 be, and push again.",
-            )
-        }
+        GitPushError::RefInUnexpectedLocation(_) => user_error_with_hint(
+            err.to_string(),
+            "Try fetching from the remote, then make the branch point to where you want it to be, \
+             and push again.",
+        ),
         _ => user_error(err),
     })?;
     writer.flush(ui)?;

lib/src/git.rs

@@ -1208,9 +1208,6 @@ pub enum GitPushError {
         name = REMOTE_NAME_FOR_LOCAL_GIT_REPO
     )]
     RemoteReservedForLocalGitRepo,
-    // TODO: Delete this? It should never trigger
-    #[error("The push conflicts with changes made on the remote (it is not fast-forwardable).")]
-    NotFastForward,
     #[error("Refusing to push a branch that unexpectedly moved on the remote. {}",
             render_ref_in_unexpected_location_details(.0)
     )]
@@ -1458,12 +1455,7 @@ fn push_refs(
         push_options.remote_callbacks(callbacks);
         remote
             .push(refspecs, Some(&mut push_options))
-            .map_err(|err| match (err.class(), err.code()) {
-                (git2::ErrorClass::Reference, git2::ErrorCode::NotFastForward) => {
-                    GitPushError::NotFastForward
-                }
-                _ => GitPushError::InternalGitError(err),
-            })
+            .map_err(GitPushError::InternalGitError)
     };
     if !failed_push_negotiations.is_empty() {
         // If the push negotiation returned an error, `remote.push` would not