substitute-binary: Skip servers that use a different store prefix.

* guix/scripts/substitute-binary.scm (fetch-narinfo): Return #f when
  CACHE uses a store directory different from (%store-prefix).

substitute-binary: Call `open-cache' only when needed.

* guix/scripts/substitute-binary.scm (lookup-narinfo): Force CACHE when
  passing it to `fetch-narinfo'.
  (guix-substitute-binary): Delay calls to `open-cache'.

substitute-binary: Add a local cache.

* guix/scripts/substitute-binary.scm (%narinfo-cache-directory,
  %narinfo-ttl, %narinfo-negative-ttl): New variables.
  (with-atomic-file-output, object->fields, read-narinfo,
  write-narinfo, narinfo->string, string->narinfo, lookup-narinfo): New
  procedures.
  (fetch-narinfo): Adjust to use `read-narinfo'.
  (guix-substitute-binary): Ensure the existence of
  %NARINFO-CACHE-DIRECTORY.  Use `lookup-narinfo' instead of
  `fetch-narinfo'.

gnu: automake: Restore shebangs on files that end up in user tarballs.

* gnu/packages/autotools.scm (automake): Add `unpatch-shebangs' phase.

utils: Add `fold2'.

* gnu/packages.scm (fold2): Remove.
* guix/utils.scm (fold2): New procedure.  Generalization of the above to
  one and two lists.
* tests/utils.scm ("fold2, 1 list", "fold2, 2 lists"): New tests.

tests: Remove temporary directory created by nar.scm.

* tests/nar.scm ("write-file + restore-file with symlinks"): Add (rm-rf
  output).

store: Remove unneeded and conflicting import.

* guix/store.scm: Remove unneeded (ice-9 rdelim) import.  In Guile 2.0.9
  that module exports `read-string', which conflicts with that of (guix
  serialization).

package: Being at the empty profile is not an error.

* guix/scripts/package.scm (roll-back): Use `format', not `leave' when
  indicating "already at the empty profile".  Fixes a regression
  introduced in a2011be5dfaf2b94a1d0e3dfbcf4b512389b4711.  Reported by
  Nikita Karetnikov <nikita@karetnikov.org>.

Update `TODO'.

guix package: Add `--no-substitutes'.

* guix/scripts/package.scm (%default-options): Add `substitutes?'.
  (show-help, %options): Add and document `--no-substitutes'.
  (guix-package): Call `set-build-options' to honor `substitutes?'.

substitute-binary: Implement `--substitute'.

This allows build outputs to be transparently downloaded from
http://hydra.gnu.org, for example.

* config-daemon.ac: Check for `gzip', `bzip2', and `xz'.
* guix/config.scm.in (%gzip, %bzip2, %xz): New variable.
* guix/scripts/substitute-binary.scm (fetch): Return SIZE as a second value.
  (<narinfo>): Change `url' to `uri'.
  (make-narinfo): Rename to...
  (narinfo-maker): ... this.  Handle relative URLs.
  (fetch-narinfo): Adjust accordingly.
  (filtered-port, decompressed-port): New procedures.
  (guix-substitute-binary): Implement the `--substitute' case.
* tests/store.scm ("substitute query"): Use (%store-prefix) instead
  of (getenv "NIX_STORE_DIR").
  ("substitute"): New test.

substitute-binary: Correctly handle missing narinfos in `--query' mode.

* guix/scripts/substitute-binary.scm (guix-substitute-binary)["--query"]("have",
  "info"): Filter SUBSTITUTABLE through `narinfo?'.

nar: Add support for symlinks.

* guix/nar.scm (write-file): Add case for type `symlink'.
  (restore-file): Likewise.
* tests/nar.scm (random-file-size, make-file-tree, delete-file-tree,
  with-file-tree, file-tree-equal?, make-random-bytevector,
  populate-file): New procedures.
  (%test-dir): New variable.
  ("write-file + restore-file"): Use `%test-dir' and `file-tree-equal?'.
  ("write-file + restore-file with symlinks"): New test.

ui: Add a `warning' macro.

* guix/ui.scm (program-name, guix-warning-port): New variables.
  (warning): New macro.
  (guix-main): Parametrize PROGRAM-NAME.
* guix/scripts/build.scm, guix/scripts/download.scm,
  guix/scripts/gc.scm, guix/scripts/package.scm: Adjust to use `leave'
  and `warning' consistently.

nar: Implement restoration from Nar.

* guix/nar.scm (&nar-error, &nar-read-error): New condition types.
  (dump): New procedure.
  (write-contents)[dump]: Remove.  Use the one above instead.
  (read-contents, write-file, restore-file): New procedures.
  (%archive-version-1): New variable.

build: Pass the appropriate flags when building `libstore.a'.

* daemon.am (libstore_a_CFLAGS): Rename to...
  (libstore_a_CXXFLAGS): ... this.

gnu: shishi: Update to 1.0.2.

* gnu/packages/shishi.scm (shishi): Update to 1.0.2.
* gnu/packages/patches/shishi-gets-undeclared.patch: Remove it.
* Makefile.am (dist_patch_DATA): Adjust accordingly.

gnu: Python: fix the compilation of some modules from the standard library.

This commit enables the bz2, dbm, readline, ssl and zlib modules.

* gnu/packages/gdbm.scm: Enable the compatibility mode.
* gnu/packages/python.scm: Enable a few modules from the standard library.
* gnu/packages/patches/python-fix-dbm.patch: New file.
* Makefile.am: Add it.

Add (guix nar) and (guix serialization).

* guix/store.scm (write-int, read-int, write-long-long, read-long-long,
  write-padding, write-string, read-string, read-latin1-string,
  write-string-list, read-string-list, write-store-path,
  read-store-path, write-store-path-list, read-store-path-list): Move to
  serialization.scm.
  (write-contents, write-file): Move to nar.scm.
* guix/nar.scm, guix/serialization.scm: New files.
* Makefile.am (MODULES): Add them.

substitute-binary: Fix communication of several store paths to the daemon.

* guix/scripts/substitute-binary.scm (guix-substitute-binary)["--query"]:
  Emit blank lines only after the complete list of store paths has been
  returned.