* guix/scripts/package.scm (<manifest>, <manifest-entry>): New record
types.
(make-manifest, read-manifest, manifest->sexp, sexp->manifest,
read-manifest, write-manifest, remove-manifest-entry, manifest-remove,
manifest-installed?): New procedures.
(profile-derivation): Take a manifest as the second parameter. Use
'manifest->sexp'. Expect <manifest-entry> objects instead of
"tuples". Adjust callers accordingly.
(search-path-environment-variables): Changes 'packages' parameter to
'entries'. Rename 'package-in-manifest->package' to
'manifest-entry->package'; expect <manifest-entry> objects.
(display-search-paths): Rename 'packages' to 'entries'.
(options->installable): Change 'installed' to 'manifest'. Have
'canonicalize-deps' return name/path tuples instead of raw packages.
Rename 'package->tuple' to 'package->manifest-entry'. Use
<manifest-entry> objects instead of tuples.
(guix-package)[process-actions]: Likewise. Rename 'packages' to
'entries'.
[process-query]: Use 'manifest-entries' instead of
'manifest-packages'.
f067fc3e77