==. For comparison, use
[ "$var" = value ].$a/$b==foo/bar[ "$a/$b" = "foo/bar" ] ShellCheck found a command name that contains a ==. Most
likely, this was intended as a kind of comparison.
To compare two values, use [ value1 = value2 ]. Both the
brackets and the spaces around the = are relevant.
None, though you can quote the == to suppress the
warning.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.