Delete directories left empty after ref deletion

This is v4 of this patch series. Thanks to Peff, Junio, Jake, and Philip for their feedback about v3. I believe I have addressed all of the comments about v1 [1], v2 [2], and v3 [3].

Changes since v3:

* Insert a new first patch correcting the docstring of refname_is_safe().

* In "raceproof_create_file(): new function", tweak a comment for clarity as suggested by Peff.

* In "log_ref_setup(): separate code for create vs non-create", add a semicolon to an otherwise empty code block as requested by Junio.

* Drop the patch "try_remove_empty_parents(): don't accommodate consecutive slashes", for reasons discussed on the ML [4].

Michael

[1] http://public-inbox.org/git/[email protected]/T/#u
[2] http://public-inbox.org/git/[email protected]/T/#u
[3] http://public-inbox.org/git/[email protected]/T/#u
[4] http://public-inbox.org/git/[email protected]/
and surrounding thread.

Michael Haggerty (23):
files_rename_ref(): tidy up whitespace
refname_is_safe(): correct docstring
t5505: use "for-each-ref" to test for the non-existence of references safe_create_leading_directories_const(): preserve errno safe_create_leading_directories(): set errno on SCLD_EXISTS raceproof_create_file(): new function lock_ref_sha1_basic(): inline constant lock_ref_sha1_basic(): use raceproof_create_file() rename_tmp_log(): use raceproof_create_file() rename_tmp_log(): improve error reporting
log_ref_write(): inline function
log_ref_setup(): separate code for create vs non-create log_ref_setup(): improve robustness against races log_ref_setup(): pass the open file descriptor back to the caller log_ref_write_1(): don't depend on logfile argument log_ref_setup(): manage the name of the reflog file internally log_ref_write_1(): inline function
delete_ref_loose(): derive loose reference path from lock delete_ref_loose(): inline function try_remove_empty_parents(): rename parameter "name" -> "refname" try_remove_empty_parents(): don't trash argument contents try_remove_empty_parents(): teach to remove parents of reflogs, too files_transaction_commit(): clean up empty directories

 cache.h               |  48 ++++++-
 refs/files-backend.c  | 371 +++++++++++++++++++++++++-------------------------
 refs/refs-internal.h  |  22 ++-
 sha1_file.c           |  76 ++++++++++-
 t/t1400-update-ref.sh |  27 ++++
 t/t5505-remote.sh     |   2 +-
 6 files changed, 351 insertions(+), 195 deletions(-)

2.9.3