build-system: Add copy-build-system.

* guix/build-system/copy.scm: New file.
* guix/build/copy-build-system.scm: New file.
* Makefile.am (MODULES): Add them.
* doc/guix.texi (Build Systems): Document 'copy-build-system'.

Makefile.am

@@ -122,6 +122,7 @@ MODULES =					\
   guix/build-system/meson.scm			\
   guix/build-system/minify.scm			\
   guix/build-system/asdf.scm			\
+  guix/build-system/copy.scm			\
   guix/build-system/glib-or-gtk.scm		\
   guix/build-system/gnu.scm			\
   guix/build-system/guile.scm			\
@@ -169,6 +170,7 @@ MODULES =					\
   guix/build/go-build-system.scm		\
   guix/build/asdf-build-system.scm		\
   guix/build/bzr.scm				\
+  guix/build/copy-build-system.scm		\
   guix/build/git.scm				\
   guix/build/hg.scm				\
   guix/build/glib-or-gtk-build-system.scm	\

doc/guix.texi

@@ -6154,6 +6154,70 @@ parameters available to cargo.  It will also remove an included
 if they are defined by the crate.
 @end defvr
 
+
+@defvr {Scheme Variable} copy-build-system
+@cindex (copy build system)
+This variable is exported by @code{(guix build-system copy)}.  It
+supports builds of simple packages that don't require much compiling,
+mostly just moving files around.
+
+It adds much of the @code{gnu-build-system} packages to the set of
+inputs.  Because of this, the @code{copy-build-system} does not require
+all the boilerplate code often needed for the
+@code{trivial-build-system}.
+
+To further simplify the file installation process, an
+@code{#:install-plan} argument is exposed to let the packager specify
+which files go where.
+The install plan is a list of @code{(SOURCE TARGET [FILTERS])}.
+@code{FILTERS} are optional.
+
+@itemize
+@item When @code{SOURCE} matches a file or directory without trailing slash, install it to @code{TARGET}.
+  @itemize
+  @item If @code{TARGET} has a trailing slash, install @code{SOURCE} basename beneath @code{TARGET}.
+  @item Otherwise install @code{SOURCE} as @code{TARGET}.
+  @end itemize
+
+@item When @code{SOURCE} is a directory with a trailing slash, or when @code{FILTERS} are used,
+  the trailing slash of @code{TARGET} is implied with the same meaning
+  as above.
+  @itemize
+  @item Without @code{FILTERS}, install the full @code{SOURCE} @emph{content} to @code{TARGET}.
+  @item With @code{FILTERS} among @code{#:include}, @code{#:include-regexp}, @code{exclude},
+    @code{#:exclude-regexp}, only select files are installed depending on
+    the filters.  Each filters is specified by a list of strings.
+    @itemize
+      @item With @code{#:include}, install all the files which path suffix exactly matches
+        one of the elements in the given list.
+      @item With @code{#:include-regexp}, install all the files which subpaths match the
+        regular expressions in the given list.
+      @item The @code{#:exclude} and @code{#:exclude-regexp} filters
+        are the complement of their inclusion counterpart.  Without @code{#:include} flags,
+        install all files but those matching the exclusion filters.
+        If both inclusions and exclusions are specified, the exclusions are done
+        on top of the inclusions.
+    @end itemize
+  @end itemize
+  In all cases, the paths relative to @code{SOURCE} are preserved within
+  @code{TARGET}.
+@end itemize
+
+Examples:
+
+@itemize
+@item @code{("foo/bar" "share/my-app/")}: Install @code{bar} to @code{share/my-app/bar}.
+@item @code{("foo/bar" "share/my-app/baz")}: Install @code{bar} to @code{share/my-app/baz}.
+@item @code{("foo/" "share/my-app")}: Install the content of @code{foo} inside @code{share/my-app},
+  e.g. install @code{foo/sub/file} to @code{share/my-app/sub/file}.
+@item @code{("foo/" "share/my-app" #:include ("sub/file"))}: Install only @code{foo/sub/file} to
+@code{share/my-app/sub/file}.
+@item @code{("foo/sub" "share/my-app" #:include ("file"))}: Install @code{foo/sub/file} to
+@code{share/my-app/file}.
+@end itemize
+@end defvr
+
+
 @cindex Clojure (programming language)
 @cindex simple Clojure build system
 @defvr {Scheme Variable} clojure-build-system

guix/build-system/copy.scm

@@ -0,0 +1,143 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2019 Julien Lepiller <julien@lepiller.eu>
+;;; Copyright © 2020 Pierre Neidhardt <mail@ambrevar.xyz>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix build-system copy)
+  #:use-module (guix store)
+  #:use-module (guix utils)
+  #:use-module (guix derivations)
+  #:use-module (guix search-paths)
+  #:use-module (guix build-system)
+  #:use-module (guix build-system gnu)
+  #:use-module (guix packages)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
+  #:export (%copy-build-system-modules
+            default-glibc
+            lower
+            copy-build
+            copy-build-system))
+
+;; Commentary:
+;;
+;; Standard build procedure for simple packages that don't require much
+;; compilation, mostly just copying files around.  This is implemented as an
+;; extension of `gnu-build-system'.
+;;
+;; Code:
+
+(define %copy-build-system-modules
+  ;; Build-side modules imported by default.
+  `((guix build copy-build-system)
+    ,@%gnu-build-system-modules))
+
+(define (default-glibc)
+  "Return the default glibc package."
+  ;; Do not use `@' to avoid introducing circular dependencies.
+  (let ((module (resolve-interface '(gnu packages base))))
+    (module-ref module 'glibc)))
+
+(define* (lower name
+                #:key source inputs native-inputs outputs system target
+                (glibc (default-glibc))
+                #:allow-other-keys
+                #:rest arguments)
+  "Return a bag for NAME from the given arguments."
+  (define private-keywords
+    '(#:source #:target #:inputs #:native-inputs))
+
+  (bag
+    (name name)
+    (system system)
+    (host-inputs `(,@(if source
+                         `(("source" ,source))
+                         '())
+                   ,@inputs
+                   ;; Keep the standard inputs of 'gnu-build-system'.
+                   ,@(standard-packages)))
+    (build-inputs native-inputs)
+    (outputs outputs)
+    (build copy-build)
+    (arguments (strip-keyword-arguments private-keywords arguments))))
+
+(define* (copy-build store name inputs
+                     #:key (guile #f)
+                     (outputs '("out"))
+                     (install-plan ''(("." (".") "./")))
+                     (search-paths '())
+                     (out-of-source? #t)
+                     (validate-runpath? #t)
+                     (patch-shebangs? #t)
+                     (strip-binaries? #t)
+                     (strip-flags ''("--strip-debug"))
+                     (strip-directories ''("lib" "lib64" "libexec"
+                                           "bin" "sbin"))
+                     (phases '(@ (guix build copy-build-system)
+                                 %standard-phases))
+                     (system (%current-system))
+                     (imported-modules %copy-build-system-modules)
+                     (modules '((guix build copy-build-system)
+                                (guix build utils))))
+  "Build SOURCE using INSTALL-PLAN, and with INPUTS."
+  (define builder
+    `(begin
+       (use-modules ,@modules)
+       (copy-build #:source ,(match (assoc-ref inputs "source")
+                               (((?  derivation? source))
+                                (derivation->output-path source))
+                               ((source)
+                                source)
+                               (source
+                                source))
+                   #:system ,system
+                   #:outputs %outputs
+                   #:inputs %build-inputs
+                   #:install-plan ,install-plan
+                   #:search-paths ',(map search-path-specification->sexp
+                                         search-paths)
+                   #:phases ,phases
+                   #:out-of-source? ,out-of-source?
+                   #:validate-runpath? ,validate-runpath?
+                   #:patch-shebangs? ,patch-shebangs?
+                   #:strip-binaries? ,strip-binaries?
+                   #:strip-flags ,strip-flags
+                   #:strip-directories ,strip-directories)))
+
+  (define guile-for-build
+    (match guile
+      ((? package?)
+       (package-derivation store guile system #:graft? #f))
+      (#f                                         ; the default
+       (let* ((distro (resolve-interface '(gnu packages commencement)))
+              (guile  (module-ref distro 'guile-final)))
+         (package-derivation store guile system #:graft? #f)))))
+
+  (build-expression->derivation store name builder
+                                #:system system
+                                #:inputs inputs
+                                #:modules imported-modules
+                                #:outputs outputs
+                                #:guile-for-build guile-for-build))
+
+(define copy-build-system
+  (build-system
+    (name 'copy)
+    (description "The standard copy build system")
+    (lower lower)))
+
+;;; copy.scm ends here

guix/build/copy-build-system.scm

@@ -0,0 +1,165 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2019 Julien Lepiller <julien@lepiller.eu>
+;;; Copyright © 2020 Pierre Neidhardt <mail@ambrevar.xyz>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix build copy-build-system)
+  #:use-module ((guix build gnu-build-system) #:prefix gnu:)
+  #:use-module (guix build utils)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 ftw)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+  #:export (%standard-phases
+            copy-build))
+
+;; Commentary:
+;;
+;; System for building packages that don't require much compilation, mostly
+;; only to copy files around.
+;;
+;; Code:
+
+(define* (install #:key install-plan outputs #:allow-other-keys)
+  "Copy files from the \"source\" build input to the \"out\" output according to INSTALL-PLAN.
+
+An install plan is a list of plans in the form:
+
+  (SOURCE TARGET [FILTERS])
+
+In the above, FILTERS are optional.
+
+- When SOURCE matches a file or directory without trailing slash, install it to
+  TARGET.
+  - If TARGET has a trailing slash, install SOURCE basename beneath TARGET.
+  - Otherwise install SOURCE as TARGET.
+
+- When SOURCE is a directory with a trailing slash, or when FILTERS are used,
+  the trailing slash of TARGET is implied.
+  - Without FILTERS, install the full SOURCE _content_ to TARGET.
+    The paths relative to SOURCE are preserved within TARGET.
+  - With FILTERS among `#:include`, `#:include-regexp`, `#:exclude`,
+    `#:exclude-regexp`:
+    - With `#:include`, install only the paths which suffix exactly matches
+      one of the elements in the list.
+    - With `#:include-regexp`, install subpaths matching the regexps in the list.
+    - The `#:exclude*` FILTERS work similarly.  Without `#:include*` flags,
+      install every subpath but the files matching the `#:exlude*` filters.
+      If both `#:include*` and `#:exclude*` are specified, the exclusion is done
+      on the inclusion list.
+
+Examples:
+
+- `(\"foo/bar\" \"share/my-app/\")`: Install bar to \"share/my-app/bar\".
+- `(\"foo/bar\" \"share/my-app/baz\")`: Install bar to \"share/my-app/baz\".
+- `(\"foo/\" \"share/my-app\")`: Install the content of foo inside \"share/my-app\",
+  e.g. install \"foo/sub/file\" to \"share/my-app/sub/file\".
+- `(\"foo/\" \"share/my-app\" #:include (\"sub/file\"))`: Install only \"foo/sub/file\" to
+\"share/my-app/sub/file\".
+- `(\"foo/sub\" \"share/my-app\" #:include (\"file\"))`: Install \"foo/sub/file\" to
+\"share/my-app/file\"."
+  (define (install-simple source target)
+    "Install SOURCE to TARGET.
+TARGET must point to a store location.
+SOURCE may be a file or a directory.
+If a directory, the directory itself is installed, not its content.
+if TARGET ends with a '/', the source is installed underneath."
+    (let ((target (if (string-suffix? "/" target)
+                      (string-append target (basename source))
+                      target)))
+      (mkdir-p (dirname target))
+      (copy-recursively source target)))
+
+  (define (install-file file target)
+    (let ((dest (string-append target
+                               (if (string-suffix? "/" target)
+                                   (string-append "/" file)
+                                   file))))
+      (format (current-output-port) "`~a' -> `~a'~%" file dest)
+      (mkdir-p (dirname dest))
+      (copy-file file dest)))
+
+  (define* (make-file-predicate suffixes matches-regexp #:optional (default-value #t))
+    "Return a predicate that returns #t if its file argument matches the
+SUFFIXES or the MATCHES-REGEXP.  If neither SUFFIXES nor MATCHES-REGEXP is
+given, then the predicate always returns DEFAULT-VALUE."
+    (if (or suffixes matches-regexp)
+        (let* ((suffixes (or suffixes '()))
+               (regexps (map make-regexp (or matches-regexp '())))
+               (predicates (append
+                            (map (lambda (str)
+                                   (cut string-suffix? str <>))
+                                 suffixes)
+                            (map (lambda (regexp)
+                                   (cut regexp-exec regexp <>))
+                                 regexps))))
+          (lambda (file)
+            (any (cut <> file) predicates)))
+        (const default-value)))
+
+  (define* (install-file-list source target #:key include exclude include-regexp exclude-regexp)
+    ;; We must use switch current directory to source so that `find-files'
+    ;; returns file paths relative to source.
+    (with-directory-excursion source
+      (let* ((exclusion-pred (negate (make-file-predicate exclude exclude-regexp #f)))
+             (inclusion-pred (make-file-predicate include include-regexp))
+             (file-list
+              (filter! exclusion-pred
+                       (find-files "." (lambda (file _stat)
+                                         (inclusion-pred file))))))
+        (map (cut install-file <> (if (string-suffix? "/" target)
+                                      target
+                                      (string-append target "/")))
+             file-list))))
+
+  (define* (install source target #:key include exclude include-regexp exclude-regexp)
+    (set! target (string-append (assoc-ref outputs "out") "/" target))
+    (let ((filters? (or include exclude include-regexp exclude-regexp)))
+      (when (and (not (file-is-directory? source))
+                 filters?)
+        (error "Cannot use filters when SOURCE is a file."))
+      (let ((multi-files-in-source?
+             (or (string-suffix? "/" source)
+                 (and (file-is-directory? source)
+                      filters?))))
+        (if multi-files-in-source?
+            (install-file-list source target
+                               #:include include
+                               #:exclude exclude
+                               #:include-regexp include-regexp
+                               #:exclude-regexp exclude-regexp)
+            (install-simple source target)))))
+
+  (for-each (lambda (plan) (apply install plan)) install-plan)
+  #t)
+
+(define %standard-phases
+  ;; Everything is as with the GNU Build System except for the `configure'
+  ;; , `build', `check' and `install' phases.
+  (modify-phases gnu:%standard-phases
+    (delete 'bootstrap)
+    (delete 'configure)
+    (delete 'build)
+    (delete 'check)
+    (replace 'install install)))
+
+(define* (copy-build #:key inputs (phases %standard-phases)
+                     #:allow-other-keys #:rest args)
+  "Build the given package, applying all of PHASES in order."
+  (apply gnu:gnu-build #:inputs inputs #:phases phases args))
+
+;;; copy-build-system.scm ends here