The build procedure learned PAGER_ENV knob that lists what default
environment variable settings to export for popular pagers.  This
mechanism is used to tweak the default settings to MORE on FreeBSD.

* ew/build-time-pager-tweaks:
  pager: move pager-specific setup into the build

"git pack-objects" has a few options that tell it not to pack
objects found in certain packfiles, which require it to scan .idx
files of all available packs.  The codepaths involved in these
operations have been optimized for a common case of not having any
non-local pack and/or any .kept pack.

* jk/pack-objects-optim:
  pack-objects: compute local/ignore_pack_keep early
  pack-objects: break out of want_object loop early
  find_pack_entry: replace last_found_pack with MRU cache
  add generic most-recently-used list
  sha1_file: drop free_pack_by_name
  t/perf: add tests for many-pack scenarios

Allowing PAGER_ENV to be set at build-time allows us to move
pager-specific knowledge out of our build.  This allows us to
set a better default for FreeBSD more(1), which pretends not to
understand ANSI color escapes if the MORE environment variable
is left empty, but accepts the same variables as less(1)

Originally-from:
 https://public-inbox.org/git/xmqq61piw4yf.fsf@gitster.dls.corp.google.com/

Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

There are a few places in Git that would benefit from a fast
most-recently-used cache (e.g., the list of packs, which we
search linearly but would like to order based on locality).
This patch introduces a generic list that can be used to
store arbitrary pointers in most-recently-used order.

The implementation is just a doubly-linked list, where
"marking" an item as used moves it to the front of the list.
Insertion and marking are O(1), and iteration is O(n).

There's no lookup support provided; if you need fast
lookups, you are better off with a different data structure
in the first place.

There is also no deletion support. This would not be hard to
do, but it's not necessary for handling pack structs, which
are created and never removed.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Build clean-up.

* nd/test-helpers:
  t/test-lib.sh: fix running tests with --valgrind
  Makefile: use VCSSVN_LIB to refer to svn library
  Makefile: drop extra dependencies for test helpers

Makefile assumed that -lrt is always available on platforms that
want to use clock_gettime() and CLOCK_MONOTONIC, which is not a
case for recent Mac OS X.  The necessary symbols are often found in
libc on many modern systems and having -lrt on the command line, as
long as the library exists, had no effect, but when the platform
removes librt.a that is a different matter--having -lrt will break
the linkage.

This change could be seen as a regression for those who do need to
specify -lrt, as they now specifically ask for NEEDS_LIBRT when
building. Hopefully they are in the minority these days.

* rw/make-needs-librt:
  config.mak.uname: define NEEDS_LIBRT under Linux, for now
  Makefile: add NEEDS_LIBRT to optionally link with librt

The API to iterate over all the refs (i.e. for_each_ref(), etc.)
has been revamped.

* mh/ref-iterators:
  for_each_reflog(): reimplement using iterators
  dir_iterator: new API for iterating over a directory tree
  for_each_reflog(): don't abort for bad references
  do_for_each_ref(): reimplement using reference iteration
  refs: introduce an iterator interface
  ref_resolves_to_object(): new function
  entry_resolves_to_object(): rename function from ref_resolves_to_object()
  get_ref_cache(): only create an instance if there is a submodule
  remote rm: handle symbolic refs correctly
  delete_refs(): add a flags argument
  refs: use name "prefix" consistently
  do_for_each_ref(): move docstring to the header file
  refs: remove unnecessary "extern" keywords

There are certain house-keeping tasks that need to be performed at
the very beginning of any Git program, and programs that are not
built-in commands had to do them exactly the same way as "git"
potty does.  It was easy to make mistakes in one-off standalone
programs (like test helpers).  A common "main()" function that
calls cmd_main() of individual program has been introduced to
make it harder to make mistakes.

* jk/common-main:
  mingw: declare main()'s argv as const
  common-main: call git_setup_gettext()
  common-main: call restore_sigpipe_to_default()
  common-main: call sanitize_stdfds()
  common-main: call git_extract_argv0_path()
  add an extra level of indirection to main()

More markings of messages for i18n, with updates to various tests
to pass GETTEXT_POISON tests.

One patch from the original submission dropped due to conflicts
with jk/upload-pack-hook, which is still in flux.

* va/i18n-even-more: (38 commits)
  t5541: become resilient to GETTEXT_POISON
  i18n: branch: mark comment when editing branch description for translation
  i18n: unmark die messages for translation
  i18n: submodule: escape shell variables inside eval_gettext
  i18n: submodule: join strings marked for translation
  i18n: init-db: join message pieces
  i18n: remote: allow translations to reorder message
  i18n: remote: mark URL fallback text for translation
  i18n: standardise messages
  i18n: sequencer: add period to error message
  i18n: merge: change command option help to lowercase
  i18n: merge: mark messages for translation
  i18n: notes: mark options for translation
  i18n: notes: mark strings for translation
  i18n: transport-helper.c: change N_() call to _()
  i18n: bisect: mark strings for translation
  t5523: use test_i18ngrep for negation
  t4153: fix negated test_i18ngrep call
  t9003: become resilient to GETTEXT_POISON
  tests: unpack-trees: update to use test_i18n* functions
  ...

We unconditionally link with librt, when HAVE_CLOCK_GETTIME is defined.
But clock_gettime() has been available in most libc implementations for
some time now (e.g., for glibc since version 2.17) and no longer
requires linking with librt. Furthermore, commit a6c3c63 (configure.ac:
check for clock_gettime() and CLOCK_MONOTONIC) will automatically
determined which library (libc or librt) is required for linking when
checking for clock_gettime().

The assumption to unconditionally link with librt was OK, since either
almost every Unix-like system provides a version of librt for backwards
compatibility or other systems, namely Windows or OS X, never provided
clock_gettime(). However, in the latest release of OS X (macOS Sierra),
this function has been added to OS X libc version. As a result, when
running the configuration script, HAVE_CLOCK_GETTIME is set and since
librt is not present, it causes a linker error.

This patches requires those not building via the configuration scripts
to define NEEDS_LIBRT in addition to HAVE_CLOCK_GETTIME, if needed.

Signed-off-by: Ronald Wampler <rdwampler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>