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From: Jeff King <>
Subject: [PATCH] t7800: don't rely on reuse_worktree_file()
Date: Thu, 16 Jan 2020 13:19:40 -0500
Message-ID: <> (raw)

A test in t7800 tries to make sure that when git-difftool runs an
external tool that fails, it stops looking at files. Our fake failing
tool prints the file name it was asked to diff before exiting non-zero,
and then we confirm the output contains only that file.

However, this subtly relies on our internal reuse_worktree_file().
Because we're diffing between branches, the command run by difftool
might see:

  - the git-stored filename (e.g., "file"), if we decided that the
    working tree contents were up-to-date with the object in the index
    and HEAD, and we could reuse them

  - a temporary filename (e.g. "/tmp/abc123_file") if we had to dump the
    contents from the object database

If the latter case happens, then the test fails, because it's expecting
the string "file". I discovered this when debugging something unrelated
with reuse_worktree_file(). I _thought_ it should be able to be
triggered by a racy-git situation, but running:

  ./ --stress --run=2,13

never seems to fail. However, by my reading of reuse_worktree_file(),
this would probably always fail under Cygwin, because it sets
NO_FAST_WORKING_DIRECTORY. At any rate, since reuse_worktree_file()
is meant to be an optimization that may or may not trigger, our test
should be robust either way.

Instead of checking the filename, let's just make sure we got a single
line of output (which would not be true if we continued after the first

Signed-off-by: Jeff King <>
 t/ | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/t/ b/t/
index 6bac9ed180..29b92907e2 100755
--- a/t/
+++ b/t/
@@ -125,15 +125,14 @@ test_expect_success 'difftool stops on error with --trust-exit-code' '
 	test_when_finished "rm -f for-diff .git/fail-right-file" &&
 	test_when_finished "git reset -- for-diff" &&
 	write_script .git/fail-right-file <<-\EOF &&
-	echo "$2"
+	echo failed
 	exit 1
 	>for-diff &&
 	git add for-diff &&
-	echo file >expect &&
 	test_must_fail git difftool -y --trust-exit-code \
 		--extcmd .git/fail-right-file branch >actual &&
-	test_cmp expect actual
+	test_line_count = 1 actual
 test_expect_success 'difftool honors exit status if command not found' '

             reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16 18:19 Jeff King [this message]
2020-01-16 21:08 ` Johannes Schindelin
2020-01-16 22:48 ` Junio C Hamano

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