git/t/t5615-alternate-env.sh
Jeff King 9be795fbce t5615: avoid re-using descriptor 4
File descriptors 3 and 4 are special in our test suite, as
they link back to the test script's original stdout and
stderr. Normally this isn't something tests need to worry
about: they are free to clobber these descriptors for
sub-commands without affecting the overall script.

But there's one very special thing about descriptor 4: since
d88785e424 (test-lib: set BASH_XTRACEFD automatically,
2016-05-11), we ask bash to output "set -x" output to it by
number. This goes to _any_ descriptor 4, even if it no
longer points to the place it did when we set BASH_XTRACEFD.

But in t5615, we run a shell loop with descriptor 4
redirected.  As a result, t5615 works with non-bash shells
even with "-x". And it works with bash without "-x". But the
combination of "bash t5615-alternate-env.sh -x" gets a test
failure (because our "set -x" output pollutes one of the
files).

We can fix this by using any descriptor _except_ the magical
4. So let's switch arbitrarily to using 5/6 in this loop,
not 3/4.

Another alternative is to use a different descriptor for
BASH_XTRACEFD. But picking an unused one turns out to be
hard. Most shells limit us to 9 numbered descriptors. Bash
can handle more, but:

  - while the BASH_XTRACEFD is specific to bash, GIT_TRACE=4
    has a similar problem, and would affect all shells

  - constructs like "999>/dev/null" are synticatically
    invalid to non-bash shells. So we have to actually bury
    it inside an eval, which creates more complications.

Of the numbers 1-9, you might think that "9" would be less
used than "4". But it's not; many of our scripts use
descriptors 8 and 9 (probably under the assumption that they
are high and therefore unused). The least-used descriptor is
currently "7". We could switch to that, but we're just
trading one magic number for another.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-12-08 09:03:38 -08:00

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#!/bin/sh
test_description='handling of alternates in environment variables'
. ./test-lib.sh
check_obj () {
alt=$1; shift
while read obj expect
do
echo "$obj" >&5 &&
echo "$obj $expect" >&6
done 5>input 6>expect &&
GIT_ALTERNATE_OBJECT_DIRECTORIES=$alt \
git "$@" cat-file --batch-check='%(objectname) %(objecttype)' \
<input >actual &&
test_cmp expect actual
}
test_expect_success 'create alternate repositories' '
git init --bare one.git &&
one=$(echo one | git -C one.git hash-object -w --stdin) &&
git init --bare two.git &&
two=$(echo two | git -C two.git hash-object -w --stdin)
'
test_expect_success 'objects inaccessible without alternates' '
check_obj "" <<-EOF
$one missing
$two missing
EOF
'
test_expect_success 'access alternate via absolute path' '
check_obj "$PWD/one.git/objects" <<-EOF
$one blob
$two missing
EOF
'
test_expect_success 'access multiple alternates' '
check_obj "$PWD/one.git/objects:$PWD/two.git/objects" <<-EOF
$one blob
$two blob
EOF
'
# bare paths are relative from $GIT_DIR
test_expect_success 'access alternate via relative path (bare)' '
git init --bare bare.git &&
check_obj "../one.git/objects" -C bare.git <<-EOF
$one blob
EOF
'
# non-bare paths are relative to top of worktree
test_expect_success 'access alternate via relative path (worktree)' '
git init worktree &&
check_obj "../one.git/objects" -C worktree <<-EOF
$one blob
EOF
'
# path is computed after moving to top-level of worktree
test_expect_success 'access alternate via relative path (subdir)' '
mkdir subdir &&
check_obj "one.git/objects" -C subdir <<-EOF
$one blob
EOF
'
# set variables outside test to avoid quote insanity; the \057 is '/',
# which doesn't need quoting, but just confirms that de-quoting
# is working.
quoted='"one.git\057objects"'
unquoted='two.git/objects'
test_expect_success 'mix of quoted and unquoted alternates' '
check_obj "$quoted:$unquoted" <<-EOF
$one blob
$two blob
EOF
'
test_expect_success !MINGW 'broken quoting falls back to interpreting raw' '
mv one.git \"one.git &&
check_obj \"one.git/objects <<-EOF
$one blob
EOF
'
test_done