This patch fixes the following issue:
When we found the commit in the graph in lookup_commit_in_graph(), but
the commit is missing from the repository, we will try
promisor_remote_get_direct() and then enter another loop.

Then we will go into an endless loop:
  git fetch -> deref_without_lazy_fetch() ->
    lookup_commit_in_graph() -> repo_has_object_file() ->
      promisor_remote_get_direct() -> fetch_objects() ->
        git fetch (a new loop round)

Changes since v1:

* add run_with_limited_processses() to test-lib so that we can use it to
  limit forking subprocesses. As we didn't check the return value of
  promise_remote_get_direct(), "git fetch" would finally succeed due to:

    error: cannot fork() for -c: Resource temporarily unavailable
    fatal: promisor-remote: unable to fork off fetch subprocess

* Rename test repositories, reference name and use GIT_TRACE to observe
  the fetch process.

Han Xin (2):
  test-lib.sh: add limited processes to test-lib
  commit-graph.c: no lazy fetch in lookup_commit_in_graph()

 commit-graph.c                             |  2 +-
 t/t5329-no-lazy-fetch-with-commit-graph.sh | 47 ++++++++++++++++++++++
 t/test-lib.sh                              |  9 +++++
 3 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100755 t/t5329-no-lazy-fetch-with-commit-graph.sh

Range-diff against v1:
1:  ebc14bfd5e < -:  ---------- commit-graph.c: no lazy fetch in lookup_commit_in_graph()
-:  ---------- > 1:  442a4c351d test-lib.sh: add limited processes to test-lib
-:  ---------- > 2:  d3a99a5c5a commit-graph.c: no lazy fetch in lookup_commit_in_graph()
-- 
2.36.1