Code clean-up.

* jk/pack-name-cleanups:
  index-pack: make pointer-alias fallbacks safer
  replace snprintf with odb_pack_name()
  odb_pack_keep(): stop generating keepfile name
  sha1_file.c: make pack-name helper globally accessible
  move odb_* declarations out of git-compat-util.h

The odb_pack_keep() function generates the name of a .keep
file and opens it. This has two problems:

  1. It requires a fixed-size buffer to create the filename
     and doesn't notice when the result is truncated.

  2. Of the two callers, one sometimes wants to open a
     filename it already has, which makes things awkward (it
     has to do so manually, and skips the leading-directory
     creation).

Instead, let's have odb_pack_keep() just open the file.
Generating the name isn't hard, and a future patch will
switch callers over to odb_pack_name() anyway.

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

In 4ac9006f832 (real_path: have callers use real_pathdup and
strbuf_realpath, 2016-12-12), we changed the xstrdup(real_path())
pattern to use real_pathdup() directly.

The problem with this change is that real_path() calls
strbuf_realpath() with die_on_error = 1 while real_pathdup() calls
it with die_on_error = 0. Meaning that in cases where real_path()
causes Git to die() with an error message, real_pathdup() is silent
and returns NULL instead.

The callers, however, are ill-prepared for that change, as they expect
the return value to be non-NULL (and otherwise the function died
with an appropriate error message).

Fix this by extending real_pathdup()'s signature to accept the
die_on_error flag and simply pass it through to strbuf_realpath(),
and then adjust all callers after a careful audit whether they would
handle NULLs well.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

When core.logallrefupdates is true, we only create a new reflog for refs
that are under certain well-known hierarchies. The reason is that we
know that some hierarchies (like refs/tags) are not meant to change, and
that unknown hierarchies might not want reflogs at all (e.g., a
hypothetical refs/foo might be meant to change often and drop old
history immediately).

However, sometimes it is useful to override this decision and simply log
for all refs, because the safety and audit trail is more important than
the performance implications of keeping the log around.

This patch introduces a new "always" mode for the core.logallrefupdates
option which will log updates to everything under refs/, regardless
where in the hierarchy it is (we still will not log things like
ORIG_HEAD and FETCH_HEAD, which are known to be transient).

Based-on-patch-by: Jeff King <peff@peff.net>
Signed-off-by: Cornelius Weig <cornelius.weig@tngtech.com>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

"git grep" has been taught to optionally recurse into submodules.

* bw/grep-recurse-submodules:
  grep: search history of moved submodules
  grep: enable recurse-submodules to work on <tree> objects
  grep: optionally recurse into submodules
  grep: add submodules as a grep source type
  submodules: load gitmodules file from commit sha1
  submodules: add helper to determine if a submodule is initialized
  submodules: add helper to determine if a submodule is populated
  real_path: canonicalize directory separators in root parts
  real_path: have callers use real_pathdup and strbuf_realpath
  real_path: create real_pathdup
  real_path: convert real_path_internal to strbuf_realpath
  real_path: resolve symlinks by hand

Migrate callers of real_path() who duplicate the retern value to use
real_pathdup or strbuf_realpath.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

There are three codepaths that use a variable whose name is
pack_compression_level to affect how objects and deltas sent to a
packfile is compressed.  Unlike zlib_compression_level that controls
the loose object compression, however, this variable was static to
each of these codepaths.  Two of them read the pack.compression
configuration variable, using core.compression as the default, and
one of them also allowed overriding it from the command line.

The other codepath in bulk-checkin did not pay any attention to the
configuration.

Unify the configuration parsing to git_default_config(), where we
implement the parsing of core.loosecompression and core.compression
and make the former override the latter, by moving code to parse
pack.compression and also allow core.compression to give default to
this variable.

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

Allow the default abbreviation length, which has historically been
7, to scale as the repository grows.  The logic suggests to use 12
hexdigits for the Linux kernel, and 9 to 10 for Git itself.

* lt/abbrev-auto:
  abbrev: auto size the default abbreviation
  abbrev: prepare for new world order
  abbrev: add FALLBACK_DEFAULT_ABBREV to prepare for auto sizing

"git ls-files" learned "--recurse-submodules" option that can be
used to get a listing of tracked files across submodules (i.e. this
only works with "--cached" option, not for listing untracked or
ignored files).  This would be a useful tool to sit on the upstream
side of a pipe that is read with xargs to work on all working tree
files from the top-level superproject.

* bw/ls-files-recurse-submodules:
  ls-files: add pathspec matching for submodules
  ls-files: pass through safe options for --recurse-submodules
  ls-files: optionally recurse into submodules
  git: make super-prefix option

Add a super-prefix environment variable 'GIT_INTERNAL_SUPER_PREFIX'
which can be used to specify a path from above a repository down to its
root.  When such a super-prefix is specified, the paths reported by Git
are prefixed with it to make them relative to that directory "above".
The paths given by the user on the command line
(e.g. "git subcmd --output-file=path/to/a/file" and pathspecs) are taken
relative to the directory "above" to match.

The immediate use of this option is by commands which have a
--recurse-submodule option in order to give context to submodules about
how they were invoked.  This option is currently only allowed for
builtins which support a super-prefix.

Signed-off-by: Brandon Williams <bmwill@google.com>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>