* guix/packages.scm (package-derivation)[intern]: New procedure. Pass
#t as the `recursive?' argument, instead of #f.
[expand-input]: New procedure, with code formerly in the body.
Support inputs where the input is a procedure returning a file name or
an <origin>.
Use `expand-input' in the body.
* tests/packages.scm ("trivial with system-dependent input"): New test.
* tests/builders.scm (%bootstrap-inputs, %bootstrap-guile): New
variables.
("gnu-build"): Use them, by setting `#:implicit-inputs? #f' and `#:guile'.
* tests/packages.scm (%bootstrap-inputs, %bootstrap-guile): New
variables.
("trivial"): Pass `#:guile %bootstrap-guile'.
("GNU Hello"): Use `package-with-explicit-inputs' to use
%BOOTSTRAP-GUILE and %BOOTSTRAP-INPUTS.
* guix/build-system/trivial.scm: New file.
* Makefile.am (MODULES): Add it.
* tests/packages.scm ("trivial"): New test.
* guix/packages.scm (package-derivation): Allow SOURCE to be #f.
* guix/packages.scm (package-transitive-inputs): New procedure.
(package-derivation): Use it to compute INPUTS.
* tests/packages.scm (dummy-package): New macro.
("package-transitive-inputs"): New test.
* guix/packages.scm (<location>): New record type.
(location, source-properties->location): New procedures.
(<package>)[location]: New field.
* tests/packages.scm ("GNU Hello"): Test `package-location'.
* Makefile.am (MODULES): Add `guix/packages.scm' and `distro/base.scm'.
(TESTS): Add `tests/packages.scm'.
(EXTRA_DIST): New variable.
* guix/packages.scm, distro/base.scm, tests/packages.scm: New files.
* guix/http.scm (http-fetch): Make `name' an optional argument, to match
the expectations of `package-source-derivation'.