GNU Make: export AWS_PROFILE with `:=`, `=` and `?=`

README.md

With export AWS_PROFILE :=

$ cat Makefile
.PHONY: test

export AWS_PROFILE := acme
export AWS_REGION := us-west-2

test:
        @echo "AWS_PROFILE=$(AWS_PROFILE) (origin: $(origin AWS_PROFILE))"
        @echo "AWS_REGION=$(AWS_REGION) (origin: $(origin AWS_REGION))"

$ make
AWS_PROFILE=acme (origin: file)
AWS_REGION=us-west-2 (origin: file)

$ make AWS_PROFILE=hoge
AWS_PROFILE=hoge (origin: command line)
AWS_REGION=us-west-2 (origin: file)

$ AWS_PROFILE=fuga make
AWS_PROFILE=acme (origin: file)
AWS_REGION=us-west-2 (origin: file)

$ (export AWS_PROFILE=vaa && make)
AWS_PROFILE=acme (origin: file)
AWS_REGION=us-west-2 (origin: file)

With export AWS_PROFILE ?=

$ cat Makefile
.PHONY: test

export AWS_PROFILE ?= acme
export AWS_REGION ?= us-west-2

test:
        @echo "AWS_PROFILE=$(AWS_PROFILE) (origin: $(origin AWS_PROFILE))"
        @echo "AWS_REGION=$(AWS_REGION) (origin: $(origin AWS_REGION))"

$ make
AWS_PROFILE=acme (origin: file)
AWS_REGION=us-west-2 (origin: file)

$ make AWS_PROFILE=hoge
AWS_PROFILE=hoge (origin: command line)
AWS_REGION=us-west-2 (origin: file)

$ AWS_PROFILE=fuga make
AWS_PROFILE=fuga (origin: environment)
AWS_REGION=us-west-2 (origin: file)

$ (export AWS_PROFILE=vaa && make)
AWS_PROFILE=vaa (origin: environment)
AWS_REGION=us-west-2 (origin: file)

With export AWS_PROFILE =

$ cat Makefile
.PHONY: test

export AWS_PROFILE = acme
export AWS_REGION = us-west-2

test:
        @echo "AWS_PROFILE=$(AWS_PROFILE) (origin: $(origin AWS_PROFILE))"
        @echo "AWS_REGION=$(AWS_REGION) (origin: $(origin AWS_REGION))"

$ make
AWS_PROFILE=acme (origin: file)
AWS_REGION=us-west-2 (origin: file)

$ make AWS_PROFILE=hoge
AWS_PROFILE=hoge (origin: command line)
AWS_REGION=us-west-2 (origin: file)

$ AWS_PROFILE=fuga make
AWS_PROFILE=acme (origin: file)
AWS_REGION=us-west-2 (origin: file)

$ (export AWS_PROFILE=vaa && make)
AWS_PROFILE=acme (origin: file)
AWS_REGION=us-west-2 (origin: file)