More transition from "unsigned char[40]" to "struct object_id".

This needed a few merge fixups, but is mostly disentangled from other
topics.

* bc/object-id:
  remote: convert functions to struct object_id
  Remove get_object_hash.
  Convert struct object to object_id
  Add several uses of get_object_hash.
  object: introduce get_object_hash macro.
  ref_newer: convert to use struct object_id
  push_refs_with_export: convert to struct object_id
  get_remote_heads: convert to struct object_id
  parse_fetch: convert to use struct object_id
  add_sought_entry_mem: convert to struct object_id
  Convert struct ref to use object_id.
  sha1_file: introduce has_object_file helper.

* maint:
  http: treat config options sslCAPath and sslCAInfo as paths
  Documentation/diff: give --word-diff-regex=. example
  filter-branch: deal with object name vs. pathname ambiguity in tree-filter
  check-ignore: correct documentation about output
  git-p4: clean up after p4 submit failure
  git-p4: work with a detached head
  git-p4: add option to system() to return subshell status
  git-p4: add failing test for submit from detached head
  remote-http(s): support SOCKS proxies
  t5813: avoid creating urls that break on cygwin
  Escape Git's exec path in contrib/rerere-train.sh script
  allow hooks to ignore their standard input stream
  rebase-i-exec: Allow space in SHELL_PATH
  Documentation: make environment variable formatting more consistent

Use struct object_id in three fields in struct ref and convert all the
necessary places that use it.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Jeff King <peff@peff.net>

Since ec7dbd145 (receive-pack: allow hooks to ignore its
standard input stream) the pre-receive and post-receive
hooks ignore SIGPIPE. Do the same for the remaining hooks
pre-push and post-rewrite, which read from standard input.
The same arguments for ignoring SIGPIPE apply.

Include test by Jeff King which checks that SIGPIPE does not
cause pre-push hook failure. With the use of git update-ref
--stdin it is fast enough to be enabled by default.

Signed-off-by: Clemens Buchacher <clemens.buchacher@intel.com>
Signed-off-by: Jeff King <peff@peff.net>

Many allocations that is manually counted (correctly) that are
followed by strcpy/sprintf have been replaced with a less error
prone constructs such as xstrfmt.

Macintosh-specific breakage was noticed and corrected in this
reroll.

* jk/war-on-sprintf: (70 commits)
  name-rev: use strip_suffix to avoid magic numbers
  use strbuf_complete to conditionally append slash
  fsck: use for_each_loose_file_in_objdir
  Makefile: drop D_INO_IN_DIRENT build knob
  fsck: drop inode-sorting code
  convert strncpy to memcpy
  notes: document length of fanout path with a constant
  color: add color_set helper for copying raw colors
  prefer memcpy to strcpy
  help: clean up kfmclient munging
  receive-pack: simplify keep_arg computation
  avoid sprintf and strcpy with flex arrays
  use alloc_ref rather than hand-allocating "struct ref"
  color: add overflow checks for parsing colors
  drop strcpy in favor of raw sha1_to_hex
  use sha1_to_hex_r() instead of strcpy
  daemon: use cld->env_array when re-spawning
  stat_tracking_info: convert to argv_array
  http-push: use an argv_array for setup_revisions
  fetch-pack: use argv_array for index-pack / unpack-objects
  ...

We generate range strings like "1234abcd...5678efab" for use
in the the fetch and push status tables. We use fixed-size
buffers along with strcat to do so. These aren't buggy, as
our manual size computation is correct, but there's nothing
checking that this is so.  Let's switch them to strbufs
instead, which are obviously correct, and make it easier to
audit the code base for problematic calls to strcat().

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

The current callers only want to die when their transport is
prohibited. But future callers want to query the mechanism
without dying.

Let's break out a few query functions, and also save the
results in a static list so we don't have to re-parse for
each query.

Based-on-a-patch-by: Blake Burkhart <bburky@bburky.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>