store-copy: 'populate-store' can optionally deduplicate files.

Until now deduplication was performed as an additional pass after
copying files, which involve re-traversing all the files that had just
been copied.

* guix/store/deduplication.scm (copy-file/deduplicate): New procedure.
* tests/store-deduplication.scm ("copy-file/deduplicate"): New test.
* guix/build/store-copy.scm (populate-store): Add #:deduplicate?
parameter and honor it.
* tests/gexp.scm ("gexp->derivation, store copy"): Pass #:deduplicate? #f
to 'populate-store'.
* gnu/build/image.scm (initialize-root-partition): Pass #:deduplicate?
to 'populate-store'.  Pass #:deduplicate? #f to 'register-closure'.
* gnu/build/vm.scm (root-partition-initializer): Likewise.
* gnu/build/install.scm (populate-single-profile-directory): Pass
 #:deduplicate? #f to 'populate-store'.
* gnu/build/linux-initrd.scm (build-initrd): Likewise.
* guix/scripts/pack.scm (self-contained-tarball)[import-module?]: New
procedure.
[build]: Pass it as an argument to 'source-module-closure'.
* guix/scripts/pack.scm (squashfs-image)[build]: Wrap in
'with-extensions'.
* gnu/system/linux-initrd.scm (expression->initrd)[import-module?]: New
procedure.
[builder]: Pass it to 'source-module-closure'.
* gnu/system/install.scm (cow-store-service-type)[import-module?]: New
procedure.  Pass it to 'source-module-closure'.

1 files changed, 2 insertions, 1 deletions

diff --git a/tests/gexp.scm b/tests/gexp.scm
index a0e55178fa..6e92f0e4b3 100644
--- a/tests/gexp.scm
+++ b/tests/gexp.scm
@@ -736,7 +736,8 @@
                                     (zero? (logand #o222 (stat:mode st)))))))
 
                        (mkdir #$output)
-                       (populate-store '("graph") #$output)
+                       (populate-store '("graph") #$output
+                                       #:deduplicate? #f)
 
                        ;; Check whether 'populate-store' canonicalizes
                        ;; permissions and timestamps.