[PATCH v2 1/1] t1450: use mv -f when overwriting a read only file

[tboegi@web.de]

From: Torsten Bögershausen <tboegi@web.de>

test case 38 in t/t1450-fsck.sh replaces a loose blob, "$tmp" below,
with a trucated version "obj.tmp" using

mv obj.tmp "$obj"

This fails on some sytems, like older MacOS.
`man mv`
includes this information:
  The following options are available:
  -f      Do not prompt for confirmation before overwriting the destination
           path.  (The -f option overrides any previous -i or -n options.)
and further down:
  If the destination path does not have a mode which permits writing, mv
  prompts the user for confirmation as specified for the -i option.

Running the test case in debug and verbose mode `./t1450-fsck.sh -d -v`
shows this lines (which I have shortened to fit into 72 characters)

override r--r--r--  user/staff for .git/objects/fc/a75a5be3823dc0560da5?
(y/n [n]) not overwritten
fca75a5be3823dc0560da57ade678f212aeb33f6

POSIX mentions that the observed
"prompt to standard error and read a line from standard input"
should not be done if "standard input is a terminal".
So we may blame the "standard input is a terminal" logic to fail.

Side note: Answering with 'y' to the question of `mv` like this
(echo y | mv obj.tmp "$obj")
makes the test case pass.

To make things not too complicated use the most portable form
mv -f obj.tmp "$obj"

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
---

Thanks to all reviewers.
Changes since V1:
  "should not be done when" -> "should not be done if"
  Fix "mv -v": it must be "mv -f"

t/t1450-fsck.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index 16cc5d5dcb..335dcbf0af 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -548,7 +548,7 @@ test_expect_success 'rev-list --verify-objects with truncated loose blob' '
 		# Truncate the loose blob such that its header can still be
 		# parsed, but reading the object data fails mid-stream.
 		test_copy_bytes 64 <"$obj" >obj.tmp &&
-		mv obj.tmp "$obj" &&
+		mv -f obj.tmp "$obj" &&
 
 		test_must_fail git rev-list --verify-objects "$blob" 2>err &&
 		test_grep "hash mismatch" err
-- 
2.50.0.rc0.46.g7014b55638