Re: [PATCH] apply: don't use core.sharedRepository to create working tree files

This commit – eb3c027e17 ("apply: don't use core.sharedRepository to create working tree files", 2020-12-01) – seems to have introduced a new test failure in the Cygwin builds for v2.30.0-rc0, and which is still present in rc1. I'm not quite sure I understand what the expected behaviour here is, but I expect the issue is down to Cygwin's slightly odd file permission handling.

To my surprise, the test fails if the worktree is under "/cygdrive", but not if it's under "/home" within the Cygwin filesystem. I expect this is some complexity with Cygwin's mount handling, but it's not a failure mode I've seen before. I'm also going to follow up on the Cygwin mailing list to see if the folk with a better understanding of Cygwin's filesystem wrangling have a better understanding of what's going on.

Extract from the relevant section of ./t4129-apply-samemode.sh -x output, when run with that commit checked out, below:

expecting success of 4129.10 'do not use core.sharedRepository for
working tree files':
        git reset --hard &&
        test_config core.sharedRepository 0666 &&
        (
                # Remove a default ACL if possible.
                (setfacl -k newdir 2>/dev/null || true) &&
                umask 0077 &&

                # Test both files (f1) and leading dirs (d)
                mkdir d &&
                touch f1 d/f2 &&
                git add f1 d/f2 &&
                git diff --staged >patch-f1-and-f2.txt &&

                rm -rf d f1 &&
                git apply patch-f1-and-f2.txt &&

                echo "-rw-------" >f1_mode.expected &&
                echo "drwx------" >d_mode.expected &&
                test_modebits f1 >f1_mode.actual &&
                test_modebits d >d_mode.actual &&
                test_cmp f1_mode.expected f1_mode.actual &&
                test_cmp d_mode.expected d_mode.actual
        )

++ git reset --hard
HEAD is now at e950771 initial
++ test_config core.sharedRepository 0666
++ config_dir=
++ test core.sharedRepository = -C
++ test_when_finished 'test_unconfig  '\''core.sharedRepository'\'''
++ test 0 = 0
++ test_cleanup='{ test_unconfig  '\''core.sharedRepository'\''
                } && (exit "$eval_ret"); eval_ret=$?; :'
++ git config core.sharedRepository 0666
++ setfacl -k newdir
++ true
++ umask 0077
++ mkdir d
++ touch f1 d/f2
++ git add f1 d/f2
++ git diff --staged
++ rm -rf d f1
++ git apply patch-f1-and-f2.txt
++ echo -rw-------
++ echo drwx------
++ test_modebits f1
++ ls -ld f1
++ sed -e 's|^\(..........\).*|\1|'
++ test_modebits d
++ ls -ld d
++ sed -e 's|^\(..........\).*|\1|'
++ test_cmp f1_mode.expected f1_mode.actual
++ test 2 -eq 2
++ eval 'diff -u' '"$@"'
+++ diff -u f1_mode.expected f1_mode.actual
--- f1_mode.expected    2020-12-19 16:50:20.169378700 +0000
+++ f1_mode.actual      2020-12-19 16:50:20.249126000 +0000