diff-tree.c: load notes machinery when required

Since its introduction in 7249e91 (revision.c: support --notes
command-line option, 2011-03-29), combining '--notes' with any option
that causes us to format notes (e.g., '--pretty', '--format="%N"', etc)
results in a failed assertion at runtime.

  $ git rev-list HEAD | git diff-tree --stdin --pretty=medium --notes
  commit 8f3d9f354286745c751374f5f1fcafee6b3f3136
  git: notes.c:1308: format_display_notes: Assertion `display_notes_trees' failed.
  Aborted

This failure is due to diff-tree not calling 'load_display_notes' to
initialize the notes machinery.

Ordinarily, this failure isn't triggered, because it requires passing
both '--notes' and another of the above mentioned options. In the case
of '--pretty', for example, we set 'opt->verbose_header', causing
'show_log()' to eventually call 'format_display_notes()', which expects
a non-NULL 'display_note_trees'.

Without initializing the notes machinery, 'display_note_trees' remains
NULL, and thus triggers an assertion failure.

Fix this by initializing the notes machinery after parsing our options,
and harden this behavior against regression with a test in t4013. (Note
that the added ref in this test requires updating two unrelated tests
which use 'log --all', and thus need to learn about the new refs).

Reported-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index 5ac94b390d..c39cabd320 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -95,6 +95,15 @@ test_expect_success setup '
 	git commit -m "update mode" &&
 	git checkout -f master &&
 
+	GIT_AUTHOR_DATE="2006-06-26 00:06:00 +0000" &&
+	GIT_COMMITTER_DATE="2006-06-26 00:06:00 +0000" &&
+	export GIT_AUTHOR_DATE GIT_COMMITTER_DATE &&
+	git checkout -b note initial &&
+	git update-index --chmod=+x file2 &&
+	git commit -m "update mode (file2)" &&
+	git notes add -m "note" &&
+	git checkout -f master &&
+
 	# Same merge as master, but with parents reversed. Hide it in a
 	# pseudo-ref to avoid impacting tests with --all.
 	commit=$(echo reverse |
@@ -372,6 +381,9 @@ diff --no-index --raw --no-abbrev dir2 dir
 
 diff-tree --pretty --root --stat --compact-summary initial
 diff-tree --pretty -R --root --stat --compact-summary initial
+diff-tree --pretty note
+diff-tree --pretty --notes note
+diff-tree --format=%N note
 diff-tree --stat --compact-summary initial mode
 diff-tree -R --stat --compact-summary initial mode
 EOF