Log Message:
Changes 2.3.1:

* "update-index --refresh" used to leak when an entry cannot be
  refreshed for whatever reason.

* "git fast-import" used to crash when it could not close and
  conclude the resulting packfile cleanly.

* "git blame" died, trying to free an uninitialized piece of memory.

* "git merge-file" did not work correctly in a subdirectory.

* "git submodule add" failed to squash "path/to/././submodule" to
  "path/to/submodule".

* In v2.2.0, we broke "git prune" that runs in a repository that
  borrows from an alternate object store.

* Certain older vintages of cURL give irregular output from
  "curl-config --vernum", which confused our build system.

* An earlier workaround to squelch unhelpful deprecation warnings
  from the complier on Mac OSX unnecessarily set minimum required
  version of the OS, which the user might want to raise (or lower)
  for other reasons.

* Longstanding configuration variable naming rules has been added to
  the documentation.

* The credential helper for Windows (in contrib/) used to mishandle
  a user name with an at-sign in it.

* Older GnuPG implementations may not correctly import the keyring
  material we prepare for the tests to use.

* Clarify in the documentation that "remote.<nick>.pushURL" and
  "remote.<nick>.URL" are there to name the same repository accessed
  via different transports, not two separate repositories.

* The pack bitmap support did not build with older versions of GCC.

* Reading configuration from a blob object, when it ends with a lone
  CR, use to confuse the configuration parser.

* We didn't format an integer that wouldn't fit in "int" but in
  "uintmax_t" correctly.

* "git push --signed" gave an incorrectly worded error message when
  the other side did not support the capability.

* "git fetch" over a remote-helper that cannot respond to "list"
  command could not fetch from a symbolic reference e.g. HEAD.

* The insn sheet "git rebase -i" creates did not fully honor
  core.abbrev settings.

* The tests that wanted to see that file becomes unreadable after
  running "chmod a-r file", and the tests that wanted to make sure it
  is not run as root, we used "can we write into the / directory?" as
  a cheap substitute, but on some platforms that is not a good
  heuristics.  The tests and their prerequisites have been updated to
  check what they really require.

* The configuration variable 'mailinfo.scissors' was hard to
  discover in the documentation.

* Correct a breakage to git-svn around v2.2 era that triggers
  premature closing of FileHandle.

* Even though we officially haven't dropped Perl 5.8 support, the
  Getopt::Long package that came with it does not support "--no-"
  prefix to negate a boolean option; manually add support to help
  people with older Getopt::Long package.