Dockerfile COPY {source:-...}
That is called variable substitution.
In English, it translates to this:
"Hey Docker, when you build this, COPY
the path you find the in $source
variable in to the current directory in the image (.
). If $source
is empty or absent, just use the default path obj/Docker/publish
"
$source
is an environment variable that is defined before executing docker build
.
Some references: