Fix upgrade count when there are no upgrades

There's a difference between

    cmd | wc -l

and

    x="$(cmd)"; echo "$x" | wc -l

in that the assignment in the latter removes a trailing newline **if one
exists**, but the "echo" always adds one. This means that if `cmd`
produces no output, the former has 0 lines, and the latter has 1 (empty)
line.

I've not found an easy way to fix this in a way that `wc` can tell the
difference between an empty line and a non-empty one, so I had to find a
separate way to count non-empty lines.

I did try `echo "$x" | grep . | wc -l`, but `shellcheck` complains with
[SC2126](https://github.com/koalaman/shellcheck/wiki/SC2126). The
suggested alternative, `echo "$x" | grep -c .`, causes a failure on
empty inputs (i.e. when there are no upgrades) because `grep` exits with
a failure status if no lines are selected.

My options were then to go with `grep | wc` and silence the warning, or
do `grep -c | cat` to mask the `grep` failure (again). Given that they
both have the same number of commands in the pipe, but `cat` is probably
*slightly* cheaper than `wc`, and the `cat` version doesn't require
adding a `shellcheck`-silencing comment, let's go with that.

1 files changed, 1 insertions, 1 deletions

diff --git a/adu-download b/adu-download
index 9fcf505..dff7501 100755
--- a/adu-download
+++ b/adu-download
@@ -30,7 +30,7 @@ UPDATE_TARGET="${SBINDIR}/adu-upgrade"
 apt-get -qq update
 
 upgradeable=$(apt -qq list --upgradeable 2>/dev/null)
-upgrades=$(echo "$upgradeable" | wc -l)
+upgrades=$(echo "$upgradeable" | grep -c . | cat)
 if [ "$upgrades" -eq 0 ]; then
 	exit 0
 fi