This problem was reported in
https://github.com/git-for-windows/git/issues/2677, but the problem actually
lies with git diff --raw, and it seems that the bug has been with us ever
since --intent-to-add was introduced.

Changes since v3:

 * Instead of showing the same OID in git diff-files --raw as in git
   diff-files -p for intent-to-add files, we now imitate the logic for
   modified (non-intent-to-add) files: we show the "null" OID (i.e.
   all-zero).

 * As a consequence, we no longer just undo the inadvertent change where
   intent-to-add files were reported with the empty tree instead of the
   empty blob, but we fix the bug that has been with us since
   run_diff_files() was taught about intent-to-add files, i.e. we fix the
   original bug of 425a28e0a4e (diff-lib: allow ita entries treated as "not
   yet exist in index", 2016-10-24), at long last.

Changes since v2:

 * Now we also drop the no-longer-used definition of hash_t in t2203.

Changes since v1:

 * Rebased onto sk/diff-files-show-i-t-a-as-new.
 * Verified that sk/diff-files-show-i-t-a-as-new does not completely resolve
   the issue (the --raw output still claims the empty blob as the
   post-image, although the difftool symptom "went away").
 * Amended the central patch of this PR to include a fix for the regression
   test that was introduced in sk/diff-files-show-i-t-a-as-new: it expected
   the raw diff to contain the hash of the empty tree object (which is
   incorrect no matter how you turn it: any hash in any raw diff should
   refer to blob objects).
 * Reordered the patches so that the central patch comes first (otherwise,
   the "empty tree" fix would cause a test failure in t2203).

Johannes Schindelin (2):
  diff-files --raw: show correct post-image of intent-to-add files
  difftool -d: ensure that intent-to-add files are handled correctly

 diff-lib.c            | 3 +--
 t/t2203-add-intent.sh | 5 ++---
 t/t7800-difftool.sh   | 8 ++++++++
 3 files changed, 11 insertions(+), 5 deletions(-)

base-commit: feea6946a5b746ff4ebf8ccdf959e303203a6011

Submitted-As: https://lore.kernel.org/git/pull.654.v4.git.1593107621.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.654.git.1591879139.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.654.v2.git.1592916485.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.654.v3.git.1593010066.gitgitgadget@gmail.com