* nix/nix-daemon/guix-daemon.cc (main): Check whether getenv ("PATH")
returns NULL before blindly initializing 'search_path'. Before that
'guix-daemon' would abort when run in an environment where 'PATH' is
undefined.
* nix/nix-daemon/guix-daemon.cc (main): When --no-substitutes is used,
clear NIX_SUBSTITUTERS. Before that, and after
89faa5c75c, '--no-substitutes' would
lead to attempts to use 'download-using-manifests.pl', which in
practice would gracelessly fail.
* nix/nix-daemon/guix-daemon.cc (parse_opt): Use 'settings.set' instead
of direct field access for 'buildCores', 'maxBuildJobs', and
'useSubstitutes'.
(main): Call 'settings.update' after 'argp_parse'.
* nix/nix-daemon/guix-daemon.cc (GUIX_OPT_NO_BUILD_HOOK): New macro.
(options): Add '--no-build-hook'.
(parse_opt): Handle it.
(main)[HAVE_DAEMON_OFFLOAD_HOOK]: Set 'useBuildHook' by default.
Set $NIX_BUILD_HOOK to our offload hook unless otherwise specified.
[!HAVE_DAEMON_OFFLOAD_HOOK]: Clear 'useBuildHook'.
* pre-inst-env.in: Set and export NIX_BUILD_HOOK.
* nix/scripts/offload.in, guix/scripts/offload.scm: New files.
* guix/ui.scm (show-guix-help)[internal?]: Add "offload".
* config-daemon.ac: Call 'GUIX_CHECK_UNBUFFERED_CBIP'.
Instantiate 'nix/scripts/offload'. Set 'BUILD_DAEMON_OFFLOAD'
conditional, and optionally define 'HAVE_DEAMON_OFFLOAD_HOOK' cpp
macro.
* daemon.am (nodist_pkglibexec_SCRIPTS)[BUILD_DAEMON_OFFLOAD]: Add it.
* Makefile.am (MODULES)[BUILD_DAEMON_OFFLOAD]: Add
'guix/scripts/offload.scm'.
(EXTRA_DIST)[!BUILD_DAEMON_OFFLOAD]: Likewise.
* m4/guix.m4 (GUIX_CHECK_UNBUFFERED_CBIP): New macro.
* doc/guix.texi (Setting Up the Daemon): Move most of the body to...
(Build Environment Setup): ... this. New subsection.
(Daemon Offload Setup): New subsection.
Suggested by Mark H. Weaver.
* nix/nix-daemon/guix-daemon.cc (GUIX_OPT_NO_SUBSTITUTES): New macro.
(options): Add `--no-substitutes'.
(parse_opt): Add `GUIX_OPT_NO_SUBSTITUTES' case.
(main): Leave `settings.substituters' empty when
`settings.useSubstitutes' is false.
* guix/scripts/substitute-binary.scm: New file.
* Makefile.am (MODULES): Add it.
* nix/scripts/substitute-binary.in: New file.
* config-daemon.ac: Produce nix/scripts/substitute-binary.
* daemon.am (nodist_pkglibexec_SCRIPTS): Add
nix/scripts/substitute-binary.
* guix/store.scm (substitutable-path-info): Use the
`query-substitutable-path-infos' RPC.
* nix/nix-daemon/guix-daemon.cc (main): Honor `NIX_SUBSTITUTERS'.
* pre-inst-env.in: Set `NIX_SUBSTITUTERS'.
* test-env.in: Leave `NIX_SUBSTITUTERS' unchanged. Set
`GUIX_BINARY_SUBSTITUTE_URL, and create
$NIX_STATE_DIR/substituter-data.
Run `guix-daemon' within `./pre-inst-env'.
* tests/store.scm ("substitute query"): New test.
* nix/nix-daemon/guix-daemon.cc (options)[!HAVE_CHROOT]: Mention that
`--disable-chroot' has no effect.
(main)[!HAVE_CHROOT]: Set `useChroot' to false.
