perf(repo): fetch the initial commit instead of pushing it (#39628)

Creating a repository with an initial commit, via `auto_init` or a
template with git content, pushed that commit through receive-pack and
three server-side hooks that do nothing for this internal push except
refresh server info. Fetching it into the bare repository instead makes
such repository creation about 3.7x faster locally (median 790ms to
214ms). E2E tests that create initialized repositories get about
0.2-0.3s faster each.

1. Run `update-server-info` after template content generation, which the
push's `post-receive` hook did before.
2. Remove the now unused `InternalPushingEnvironment` and
`PushOptions.LocalRefName`.

modules/git/fetch.go

@@ -18,8 +18,15 @@ import (
 // Ref: https://www.kernel.org/pub/software/scm/git/docs/git-gc.html
 func FetchRemoteTempCommit(ctx context.Context, repo, remoteRepo RepositoryFacade, commitID string) error {
 	// since it is for temporary use, we don't need to update any ref or lock anything or maintain anything
-	return gitcmd.NewCommand("fetch", "--no-tags", "--no-write-commit-graph", "--no-write-fetch-head", "--no-auto-maintenance").
-		AddDynamicArguments(gitrepo.RepoLocalPath(remoteRepo)).
-		AddDynamicArguments(commitID).
-		WithRepo(repo).Run(ctx)
+	return fetchRemoteCommand(remoteRepo, commitID).WithRepo(repo).Run(ctx)
+}
+
+// FetchRemoteCommitUpdateRef fetches a commit from a remote repository and points refName at it
+func FetchRemoteCommitUpdateRef(ctx context.Context, repo, remoteRepo RepositoryFacade, commitish, refName string) error {
+	return fetchRemoteCommand(remoteRepo, "+"+commitish+":"+refName).WithRepo(repo).RunWithStderr(ctx)
+}
+
+func fetchRemoteCommand(remoteRepo RepositoryFacade, refspec string) *gitcmd.Command {
+	return gitcmd.NewCommand("fetch", "--no-tags", "--no-write-commit-graph", "--no-write-fetch-head", "--no-auto-maintenance").
+		AddDynamicArguments(gitrepo.RepoLocalPath(remoteRepo), refspec)
 }