Git 2.14.1: t6500: error during test on musl libc

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Hi there,

While bumping Git's version for our Linux distribution to 2.14.1, I've run in to a new test failure in t6500-gc.sh. This is the output of the failing test with debug=t verbose=t:

expecting success:
        # make sure we run a background auto-gc
        test_commit make-pack &&
        git repack &&
        test_config gc.autopacklimit 1 &&
        test_config gc.autodetach true &&

        # create a ref whose loose presence we can use to detect a
pack-refs run
        git update-ref refs/heads/should-be-loose HEAD &&
        test_path_is_file .git/refs/heads/should-be-loose &&

        # now fake a concurrent gc that holds the lock; we can use our
        # shell pid so that it looks valid.
        hostname=$(hostname || echo unknown) &&
        printf "$$ %s" "$hostname" >.git/gc.pid &&

        # our gc should exit zero without doing anything
        run_and_wait_for_auto_gc &&
        test_path_is_file .git/refs/heads/should-be-loose

[master 28ecdda] make-pack
 Author: A U Thor <author@example.com>
 1 file changed, 1 insertion(+)
 create mode 100644 make-pack.t
Counting objects: 3, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (3/3), done.
Total 3 (delta 0), reused 0 (delta 0)
Auto packing the repository in background for optimum performance.
See "git help gc" for manual housekeeping.
File .git/refs/heads/should-be-loose doesn't exist.
not ok 8 - background auto gc respects lock for all operations
#
#               # make sure we run a background auto-gc
#               test_commit make-pack &&
#               git repack &&
#               test_config gc.autopacklimit 1 &&
#               test_config gc.autodetach true &&
#
#               # create a ref whose loose presence we can use to
detect a pack-refs run
#               git update-ref refs/heads/should-be-loose HEAD &&
#               test_path_is_file .git/refs/heads/should-be-loose &&
#
#               # now fake a concurrent gc that holds the lock; we can
use our
#               # shell pid so that it looks valid.
#               hostname=$(hostname || echo unknown) &&
#               printf "$$ %s" "$hostname" >.git/gc.pid &&
#
#               # our gc should exit zero without doing anything
#               run_and_wait_for_auto_gc &&
#               test_path_is_file .git/refs/heads/should-be-loose
#

# failed 1 among 8 test(s) 1..8

I admit I am mostly blind with the Git gc system. Should I use strace on the git-gc process at the end? How would I accomplish that? Is there a better way of debugging this error further?

Core system stats:

Intel x86_64 E3-1280 v3 @ 3.60 GHz musl libc 1.1.16+20 git 2.14.1, vanilla except for a patch to an earlier test due to musl's inability to cope with EUC-JP bash 4.3.48(1)-release

Thank you very much.

All the best,
- --arw

- -- 
A. Wilcox (awilfox)
Project Lead, Adélie Linux
http://adelielinux.org
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