[PATCH v2] maintenance tests: fix systemd v2.34.0-rc* test regression

Fix tests added in b681b191f92 (maintenance: add support for systemd timers on Linux, 2021-09-04) to run successfully on systems where systemd-analyze is installed, but on which there's a discrepancy between a FILE argument of "/lib/systemd/system/basic.target" and "systemd/user/git-maintenance@.service" succeeding.

There was an attempt to work around previous breakage in these tests in 670e5973992 (maintenance: fix test t7900-maintenance.sh, 2021-09-27), as noted in my [1] that commit is wrong about its assumption that we can use "/lib/systemd/system/basic.target" as a canary.argument.

To fix this let's adjust this test to test what it really should be testing: If we've got systemd-analyze reporting anything useful, we should use it to check the syntax of our just-generated "systemd/user/git-maintenance@.service" file.

Even on systems where this previously succeeded we weren't effectively doing that, because "systemd-analyze" will pass various syntax errors by and exit with a status code of 0, e.g. if the "[Unit]" section is replaced with a nonsensical "[HlaghUnfUnf]" section.

To do that ignore whatever exit code we get from "systemd-analyze verify", and filter its stderr output to extract the sorts of lines it emits on note syntax warnings and errors. We need to filter out "Failed to load", which would be emitted e.g. on the gcc135.fsffrance.org test box[1].

We also need to pipe this output to FD's 5 & 6, to avoid mixing up the trace output with our own output under "-x".

1. https://lore.kernel.org/git/211026.8635oo11jk.gmgdl@evledraar.gmail.com/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---

This test is still broken in rc2, this patch fixes it. The only update is a commit message grammar fix pointed out by Eric Sunshine, thanks!

Range-diff against v1:
1:  90172a8ddcc ! 1:  44f0cafa16e maintenance tests: fix systemd v2.34.0-rc* test regression
    @@ Commit message
         maintenance tests: fix systemd v2.34.0-rc* test regression
     
         Fix tests added in b681b191f92 (maintenance: add support for systemd
    -    timers on Linux, 2021-09-04) to run successfully no systems where
    +    timers on Linux, 2021-09-04) to run successfully on systems where
         systemd-analyze is installed, but on which there's a discrepancy
         between a FILE argument of "/lib/systemd/system/basic.target" and
         "systemd/user/git-maintenance@.service" succeeding.
    @@ Commit message
     
         To do that ignore whatever exit code we get from "systemd-analyze
         verify", and filter its stderr output to extract the sorts of lines it
    -    emits no note syntax warnings and errors. We need to filter out
    +    emits on note syntax warnings and errors. We need to filter out
         "Failed to load", which would be emitted e.g. on the
         gcc135.fsffrance.org test box[1].
     

 t/t7900-maintenance.sh | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)