`set -x` causes `$(...)` to return incorrect results

[certik]

Consider the following ci/version.sh script:

#!/usr/bin/env shell

set -ex

version=$(git describe --tags --dirty)
echo "|${version}|"

This will print:

$ shell ci/version.sh
+ version=+ git describe --tags --dirty v0.45.0-368-g7534e5ade-dirty
+ echo |+ git describe --tags --dirty v0.45.0-368-g7534e5ade-dirty|
|+ git describe --tags --dirty v0.45.0-368-g7534e5ade-dirty|

This is incorrect. Rather, it should print the following, which it does when you remove "set -x":

$ shell ci/version.sh
|v0.45.0-368-g7534e5ade-dirty|

The $version variable is incorrect with set -x.