[PATCH v2 00/25] Remove assumptions about each_ref_fn arg lifetimes

This is version two of the patch series. Aside from addressing Junio's comments about the first version, it goes significantly further than v1:

I did a manual audit of the 50 (!) functions that are used as an each_ref_fn callback to the for_each_ref()-style functions. (I hope I haven't missed any.) I checked that they do not make the assumption that the lifetimes of the refname and sha1 arguments extend past the duration of the callback invocation. There were a number of callers that got this wrong; I believe I have fixed them all.

I also changed how object_array_entry manages its name field. Like the RFC in the first version of this patch series, I change add_object_array_with_mode() to make a copy of the name before storing it in its field. But (at Peff's suggestion) I also make an optimization like that of strbuf of not copying the name if it is the empty string, but rather using a pointer to a static empty string.

After this patch series, the test suite runs without errors under valgrind even when I change refs.c:do_one_ref() to pass temporary copies of refname and sha1 to the callback functions then free them immediately. (Before this patch series, such a test failed in many places.) But it is still not enough to make Peff's jk/packed-refs-race series work correctly under the "hyperactive repository" stress-test in which the packed-refs file is made to always look stale,

    refs.c:get_packed_refs():
    -	if (refs->packed &&
    -	    !stat_validity_check(&refs->packed_validity, packed_refs_file))
    +	if (refs->packed /* &&
    +	    !stat_validity_check(&refs->packed_validity, packed_refs_file) */)

Michael Haggerty (25):
  describe: make own copy of refname
  fetch: make own copies of refnames
  add_rev_cmdline(): make a copy of the name argument
  builtin_diff_tree(): make it obvious that function wants two entries
  cmd_diff(): use an object_array for holding trees
  cmd_diff(): rename local variable "list" -> "entry"
  cmd_diff(): make it obvious which cases are exclusive of each other
  revision: split some overly-long lines
  object_array: add function object_array_filter()
  revision: use object_array_filter() in implementation of gc_boundary()
  object_array_remove_duplicates(): rewrite to reduce copying
  fsck: don't put a void*-shaped peg in a char*-shaped hole
  find_first_merges(): initialize merges variable using initializer
  find_first_merges(): remove unnecessary code
  object_array_entry: fix memory handling of the name field
  do_fetch(): reduce scope of peer_item
  do_fetch(): clean up existing_refs before exiting
  add_existing(): do not retain a reference to sha1
  show_head_ref(): do not shadow name of argument
  show_head_ref(): rename first parameter to "refname"
  string_list_add_one_ref(): rename first parameter to "refname"
  string_list_add_refs_by_glob(): add a comment about memory management
  exclude_existing(): set existing_refs.strdup_strings
  register_ref(): make a copy of the bad reference SHA-1
  refs: document the lifetime of the args passed to each_ref_fn

 bisect.c           |  5 ++--
 builtin/describe.c |  6 +++--
 builtin/diff.c     | 69 ++++++++++++++++++++++++++---------------------------
 builtin/fetch.c    | 29 ++++++++++++----------
 builtin/fsck.c     |  2 +-
 builtin/show-ref.c |  2 +-
 bundle.c           |  2 +-
 http-backend.c     |  6 ++---
 notes.c            |  9 ++++---
 object.c           | 70 ++++++++++++++++++++++++++++++++++++++++++++----------
 object.h           | 25 +++++++++++++++++--
 refs.h             | 22 ++++++++++++-----
 revision.c         | 64 +++++++++++++++++++++++++++++--------------------
 revision.h         | 32 ++++++++++++++++---------
 submodule.c        |  6 ++---
 15 files changed, 228 insertions(+), 121 deletions(-)