slashdot hack and pattern matching

[callegar]

Hi, I wonder if the documentation could be clarified with respect to root specification, the slashdot hack and pattern matching.

• Can the slashdot hack be employed also in root specification in pattern files?
• When the slashdot hack is used, are patterns matched against the full path or the stripped path? I think the first. If so would be able to specify a prefix that is applied to all the following patterns to reduce verbosity.

[cperl82]

I just stumbled upon this and found it surprising.

For example, let's say that I do some setup (e.g. take snapshots or whatever) before I run borg and when all is said and done I have a directory sysroot that I want to backup, I want sysroot to be at the base of the produced archive, and I want to exclude sysroot/home/*/.cache.

Here is an obvious way that works:

t=$(mktemp -t -d "borg-testing.XXXXXX")
mkdir -p "${t}/sysroot/home/.cache"
touch "${t}/sysroot/home/.cache/test-file"
cd "${t}" && {
    borg create                                 \
         --dry-run                              \
         --list                                 \
         --pattern '! sh:sysroot/*/.cache'      \
         test::test                             \
         "sysroot"
}
rm -rf "${t}"

This outputs:

x sysroot/home/.cache
- sysroot/home
- sysroot

The thing I found surprising, is this doesn't work:

t=$(mktemp -t -d "borg-testing.XXXXXX")
mkdir -p "${t}/sysroot/home/.cache"
touch "${t}/sysroot/home/.cache/test-file"
cd "/" && {
    borg create                                 \
         --dry-run                              \
         --list                                 \
         --pattern '! sh:sysroot/*/.cache'      \
         test::test                             \
         "${t}/./sysroot"
}
rm -rf "${t}"

This outputs:

- /tmp/borg-testing.TmaIvA/sysroot/home/.cache/test-file
- /tmp/borg-testing.TmaIvA/sysroot/home/.cache
- /tmp/borg-testing.TmaIvA/sysroot/home
- /tmp/borg-testing.TmaIvA/sysroot

For the second case to work, you have to update the pattern so it matches the paths before the slashdot removal is applied:

t=$(mktemp -t -d "borg-testing.XXXXXX")
mkdir -p "${t}/sysroot/home/.cache"
touch "${t}/sysroot/home/.cache/test-file"
cd "/" && {
    borg create                                 \
         --dry-run                              \
         --list                                 \
         --pattern '! sh:**/./sysroot/*/.cache' \
         test::test                             \
         "${t}/./sysroot"
}
rm -rf "${t}"

This outputs:

x /tmp/borg-testing.7i6eQ9/sysroot/home/.cache
- /tmp/borg-testing.7i6eQ9/sysroot/home
- /tmp/borg-testing.7i6eQ9/sysroot

I found this behavior surprising given borg help patterns says:

Be careful, your patterns must match the archived paths

In the 2nd and 3rd cases above, the archived paths are the same (i.e. they start with sysroot/...).

I'd personally prefer it if the patterns were always checked against the archived paths (so the 2nd case above would work and the 3rd would not), but I can appreciate that might break some people's setups who have discovered this along the way. So, perhaps just updating the documentation to mention this quirk is good enough.