Subject: Re: [PATCH v2] test-lib: set GIT_CEILING_DIRECTORIES to protect the surrounding repository

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Tue, 31 Aug 2021 16:40:39 +0200

On Sun, Aug 29 2021, SZEDER Gábor wrote:

> Every once in a while a test somehow manages to escape from its trash
> directory and modifies the surrounding repository, whether because of
> a bug in git itself, a bug in a test [1], or e.g. when trying to run
> tests with a shell that is, in general, unable to run our tests [2].
>
> Set GIT_CEILING_DIRECTORIES="$TRASH_DIRECTORY/.." as an additional
> safety measure to protect the surrounding repository at least from
> modifications by git commands executed in the tests (assuming that
> handling of ceiling directories during repository discovery is not
> broken, and, of course, it won't save us from regular shell commands,
> e.g. 'cd .. && rm -f ...').
>
> [1] e.g. https://public-inbox.org/git/[email-masked]
> [2] $ git symbolic-ref HEAD
>     refs/heads/master
>     $ ksh ./t2011-checkout-invalid-head.sh
>     [... a lot of "not ok" ...]
>     $ git symbolic-ref HEAD
>     refs/heads/other
>
>     (In short: 'ksh' doesn't support the 'local' builtin command,
>     which is used by 'test_oid', causing it to return with error
>     whenever it's called, leaving ZERO_OID set to empty, so when the
>     test 'checkout main from invalid HEAD' runs 'echo $ZERO_OID
>     >.git/HEAD' it writes a corrupt (not invalid) HEAD, and subsequent
>     git commands don't recognize the repository in the trash directory
>     anymore, but operate on the surrounding repo.)
>
> Signed-off-by: SZEDER Gábor <[email-masked]>
> ---
> Changes since v1:
>  - Set "$TRASH_DIRECTORY/.." instead of $GIT_BUILD_DIR.
>  - Minor commit message tweaks.
>
>  t/test-lib.sh | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index abcfbed6d6..fc1e521519 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -1343,7 +1343,8 @@ fi
>  GIT_TEMPLATE_DIR="$GIT_BUILD_DIR"/templates/blt
>  GIT_CONFIG_NOSYSTEM=1
>  GIT_ATTR_NOSYSTEM=1
> -export PATH GIT_EXEC_PATH GIT_TEMPLATE_DIR GIT_CONFIG_NOSYSTEM GIT_ATTR_NOSYSTEM
> +GIT_CEILING_DIRECTORIES="$TRASH_DIRECTORY/.."
> +export PATH GIT_EXEC_PATH GIT_TEMPLATE_DIR GIT_CONFIG_NOSYSTEM GIT_ATTR_NOSYSTEM GIT_CEILING_DIRECTORIES
>  
>  if test -z "$GIT_TEST_CMP"
>  then

For what it's worth I'm very happy with this, and have been running this
in my own daily build of git, I've occasionally ran into e.g. needing to
manually clean up my own git.git's config file because some test escaped
its trash directory.