Avoid rewriting "packed-refs" unnecessarily

This reroll make some logically small changes to v1 [1] that are textually very big:

* Invert the sense of is_packed_transaction_noop() and rename it to is_packed_transaction_needed(). This makes the logic easier to follow and document.

* Add a big comment to that function, describing the cases when it returns false positives and explaining why that isn't a problem.

* In the commit message for patch 02, gives a lot more information about the regression that it is fixing. Thanks to Eric for the suggestion.

These patches are also available as branch avoid-rewriting-packed-refs on my GitHub fork [2]. They now use mh/packed-ref-transactions as the base, since that is where Junio chose to apply v1.

Michael

[1] https://public-inbox.org/git/[email protected]/
[2] https://github.com/mhagger/git

Michael Haggerty (2):
t1409: check that packed-refs is not rewritten unnecessarily
files-backend: don't rewrite the packed-refs file unnecessarily

 refs/files-backend.c          |  18 ++++++-
 refs/packed-backend.c         |  94 +++++++++++++++++++++++++++++++++
 refs/packed-backend.h         |   9 ++++
 t/t1409-avoid-packing-refs.sh | 118 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 238 insertions(+), 1 deletion(-)
 create mode 100755 t/t1409-avoid-packing-refs.sh

2.14.1