fix(run-task): avoid unnecessary 'git fetch' call

If the condition in the if statement is true, then we've already fetched
ref from head_repo. There's no need to do so again.

Author: ahal

src/taskgraph/run-task/run-task

@@ -664,33 +664,22 @@ def git_checkout(
 
         retry_required_command(b"vcs", args, cwd=destination_path, extra_env=env)
 
-    # If a ref was provided, it might be tag, so we need to make sure we fetch
-    # those. This is explicitly only done when base and head repo match,
-    # because it is the only scenario where tags could be present. (PRs, for
-    # example, always include an explicit rev.) Failure to do this could result
-    # in not having a tag, or worse: having an outdated version of one.
-    # `--force` is needed to be able to update an existing tag.
+    # Fetch ref
+    args = ["git", "fetch"]
     if ref and base_repo == head_repo:
-        args = [
-            "git",
-            "fetch",
-            "--tags",
-            "--force",
-            base_repo,
-            ref,
-        ]
-
-        retry_required_command(b"vcs", args, cwd=destination_path, extra_env=env)
+        # If a ref was provided, it might be tag, so we need to make sure we fetch
+        # those. This is explicitly only done when base and head repo match,
+        # because it is the only scenario where tags could be present. (PRs, for
+        # example, always include an explicit rev.) Failure to do this could result
+        # in not having a tag, or worse: having an outdated version of one.
+        # `--force` is needed to be able to update an existing tag.
+        args.extend(["--tags", "--force"])
 
-    # If a ref isn't provided, we fetch all refs from head_repo, which may be slow
-    args = [
-        "git",
-        "fetch",
-        "--no-tags",
-        head_repo,
-        ref if ref else "+refs/heads/*:refs/remotes/work/*",
-    ]
+    else:
+        args.append("--no-tags")
 
+    # If a ref isn't provided, we fetch all refs from head_repo, which may be slow.
+    args.extend([head_repo, ref if ref else "+refs/heads/*:refs/remotes/work/*"])
     retry_required_command(b"vcs", args, cwd=destination_path, extra_env=env)
 
     args = [