With many thousands of references, a simple `git rev-parse HEAD` may take
more than a second to return because it first loads all the refs into
memory even though it will never use them.

Defer loading any references until we actually need them.

Signed-off-by: Phil Hord <phil.hord@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Code cleanup.

* rs/sequencer-rewrite-file-cleanup:
  sequencer.c: check return value of close() in rewrite_file()
  sequencer: use O_TRUNC to truncate files
  sequencer: factor out rewrite_file()

A test update.

* cb/t4201-robustify:
  t4201: make use of abbreviation in the test more robust

Replace the mailing address of FSF to a URL, as FSF prefers.

* tz/fsf-address-update:
  Replace Free Software Foundation address in license notices
  Replace Free Software Foundation address in license notices

Typofix.

* ad/rebase-i-serie-typofix:
  rebase -i: fix comment typo

We used to add an empty alternate object database to the system
that does not help anything; it has been corrected.

* jk/info-alternates-fix:
  link_alt_odb_entries: make empty input a noop

Building with NO_LIBPCRE1_JIT did not disable it, which has been fixed.

* ab/pcre-v2:
  grep: fix NO_LIBPCRE1_JIT to fully disable JIT

Some error messages did not quote filenames shown in it, which have
been fixed.

* sr/wrapper-quote-filenames:
  wrapper.c: consistently quote filenames in error messages