This is a follow up commit for f932729c (memoize common git-path
"constant" files, 10-Aug-2015).

The many function calls to git_path() are replaced by
git_path_commit_editmsg() and which thus eliminates the need to repeatedly
compute the location of "COMMIT_EDITMSG".

Mentored-by: Lars Schneider <larsxschneider@gmail.com>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

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

* maint:
  Git 2.8.4

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

The "are we talking with TTY, doing an interactive session?"
detection has been updated to work better for "Git for Windows".

* kb/msys2-tty:
  mingw: make isatty() recognize MSYS2's pseudo terminals (/dev/pty*)

"git difftool" learned to handle unmerged paths correctly in
dir-diff mode.

* da/difftool:
  difftool: handle unmerged files in dir-diff mode
  difftool: initialize variables for readability

A couple of bugs around core.autocrlf have been fixed.

* tb/core-eol-fix:
  convert.c: ident + core.autocrlf didn't work
  t0027: test cases for combined attributes
  convert: allow core.autocrlf=input and core.eol=crlf
  t0027: make commit_chk_wrnNNO() reliable

Many commands normalize command line arguments from NFD to NFC
variant of UTF-8 on OSX, but commands in the "diff" family did
not, causing "git diff $path" to complain that no such path is
known to Git.  They have been taught to do the normalization.

* ar/diff-args-osx-precompose:
  diff: run arguments through precompose_argv

A bash-ism "local" has been removed from "git submodule" scripted
Porcelain.

* sb/submodule-helper-relative-path:
  submodule: remove bashism from shell script

The way how "submodule--helper list" signals unmatch error to its
callers has been updated.

* sb/submodule-helper-list-signal-unmatch-via-exit-status:
  submodule--helper: offer a consistent API