Problems with t6011

Hej Patrick, in case you have a second: the mv command here needs a "-f" to overwrite read-only files:

Torsten Bögershausen <tboegi@web.de> writes:

Looking at the remainder of cdbdc6bf (t: refactor tests depending on Perl substitution operator, 2025-04-03), the commit that introduced these lines, it seems that the prevailing pattern was:

	chmod +w "$packfile" &&
	perl -pe "regexp" "$packfile" >"$packfile.munged" &&
	mv "packfile.munged" $packfile"

but the original for this loop used "perl -i.bak -pe" that dealt with read-only input just fine, wihtout the need for a separate "mv".

So the lack of "-f" indeed is a bug in that "refactor" commit.

I would be more worried about using "sed" on clearly non-text files, which technically is undefined operation, and I strongly suspect that it was the reason why we used Perl to munge files that are clearly binary, like the packfiles, in the first place.

No, this is not about a quiz on regexp compatibility between Perl and sed.

Back when cdbdc6bf (t: refactor tests depending on Perl substitution operator, 2025-04-03) rewrite many use of perl with sed, the general pattern of the original scripts were

    chmod +w some_read_only_file &&
    perl -p -e "regexp to munge" some_read_only_file >some_tmp &&
    mv some_tmp some_read_only_file

persumably because the author new replacing some_read_only_file with "mv" at the last step would not work without "mv -f" in some environments (GNU does not seem to give any prompt when not running interactively, which is what happens when running t/ scripts). Replacing perl with sed would be fine as long as sed with updated regexp does the equivalent munging.

But one place used to use a different construct in the original:

    perl -i.bak -p -e "regexp to munge" some_read_only_file

With _no_ temporary file or "mv", "perl -i" allows you to replace a read-only file in place.

When we replaced the use of "perl" with "sed" in the said commit, however, because "sed -i" is not portable, we rewrote that in-place replacement to

    sed "regexp to munge" some_read_only_file >some_tmp &&
    mv some_tmp some_read_only_file

Again, unfortunately that does not work in some environment, without "mv -f".

We could run "mv -f" here, but we would then need to remove "chmod +w" and have them use "mv -f" instead at all places that were touched cdbdc6bf (t: refactor tests depending on Perl substitution operator, 2025-04-03) to be consistent (and more concise).

For now, let's make it consistent in the other direction by mimick the other places that made the target read-write before moving.

Speaking of portability, the outcome of using "sed" on non-text files is unspecified, so the entire exercise of cdbdc6bf may have needed to be reverted if people still used ancient version of "standard compliant" sed that barfs on non-text files, but these days we may be able to get away with "BSDs and GNU seem OK with it" ;-) But one fix at a time.

Reported-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

 t/t6011-rev-list-with-bad-commit.sh | 1 +
 1 file changed, 1 insertion(+)

On Tue, May 06, 2025 at 03:48:55PM -0700, Junio C Hamano wrote:

s/rewrite many use/rewrote many uses/

s/new/knew?

Ok, the fix makes sense. Thanks!

Patrick

Patrick Steinhardt <ps@pks.im> writes:

Thanks for typofixes and sanity checking.