Bug#1028190: tzdata: Possible bug in postinst

[Niels Thykier <niels@thykier.net>]

Package: tzdata
Version: 2022g-1
Severity: normal
X-Debbugs-Cc: niels@thykier.net

In the postinst, there is the following snippet:

> #! /bin/sh
> set -e
> [...]
>         # Update the time zone
>         echo $AREA/$ZONE > "$DPKG_ROOT/etc/timezone"
>         ln -nsf /usr/share/zoneinfo/$AREA/$ZONE "$DPKG_ROOT/etc/localtime.dpkg-new" && \
>             mv -f "$DPKG_ROOT/etc/localtime.dpkg-new" "$DPKG_ROOT/etc/localtime"
>         which restorecon >/dev/null 2>&1 && restorecon "$DPKG_ROOT/etc/localtime"

I think there is a bug in the `which restorecon ...` construct that can 
cause termination of the postinst rather than conditional call to 
`restorecon`.

As far as I can tell, the construct will "fail" when restorecon is present:

```
which foo >/dev/null 2>&1 && foo ; echo $?
1
```


With `set -e`, this would trigger the postinst to fail and abort the 
installation.

I think this case calls for a `if ...; then .. fi` construct or a `! 
which ... && ...`.

I feel this ought to be an RC bug. However, given I found this with 
(manual) static analysis and no one else complained, I guess this case 
is basically never triggered.  That is why I have reported as non-RC.

Thanks,
~Niels