Nested code - blocks of code inside blocks of code - is eventually necessary, but increases complexity. This is why keeping the code as flat as
possible, by avoiding unnecessary nesting, is considered a good practice.
Merging if statements when possible will decrease the nesting of the code and improve its readability.
if [ $condition1 ] ; then
if [ $condition2 ] ; then # Noncompliant
# ...
fi
fi
Will be more readable as
if [ $condition1 && $condition2 ] ; then
# ...
fi
