guix gc: Add '--free-space'.

* guix/scripts/gc.scm (show-help, %options): Add '--free-space'.
(guix-gc)[ensure-free-space]: New procedure.
Handle '--free-space'.

substitute: Sanitize the client-provided column number.

* guix/scripts/substitute.scm (client-terminal-columns): Sanitize the
client's column number.

substitute: Install the client's locale.

* guix/store.scm (set-build-options): Add #:locale parameter and honor
it.
* guix/scripts/substitute.scm (guix-substitute): Install the client's
locale.

substitute: Internationalize signature and download messages.

* guix/scripts/substitute.scm (assert-valid-narinfo): Use gettext for
messages.

substitute: Better abbreviate substitute URL in progress report.

Suggested by Danny Milosavljevic <dannym@scratchpost.org>.

* guix/build/download.scm (nar-uri-abbreviation): New procedure.
* guix/scripts/substitute.scm (process-substitution): Use it instead of
'store-path-abbreviation'.

substitute: Honor the number of columns of the client terminal.

* guix/store.scm (set-build-options): Add #:terminal-columns parameter
and honor it.
* guix/scripts/substitute.scm (client-terminal-columns): New procedure.
(guix-substitute): Use it to parameterize 'current-terminal-columns'.

guix download: Honor the number of columns of the terminal.

* guix/scripts/download.scm (guix-download): Parameterize
'current-terminal-columns'.

lint: Emit an ANSI erase-in-line sequence.

* guix/scripts/lint.scm (run-checkers): Add '\x1b[K' to progress
messages and after 'for-each'.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

environment: container: Work around read-only /etc/resolv.conf issue.

* guix/scripts/environment.scm (launch-environment/container): Mount
/etc/resolv.conf as a writable file.

challenge: Really exit with non-zero upon hash mismatch.

Reported by John Darrington.

* guix/scripts/challenge.scm (guix-challenge): Add an explicit 'exit'
call when ISSUES is empty.
* scripts/guix.in: Add comment about 'exit'.
* doc/guix.texi (Invoking guix challenge): Mention the behavior and exit
code.

emacs: Use 'build-and-use-profile' from (guix scripts package).

* guix/scripts/package.scm: Export 'build-and-use-profile'.
* emacs/guix-main.scm (process-package-actions): Use it.

import: Add Hackage updater.

* guix/import/hackage.scm (guix-package->hackage-name, hackage-package?)
  (latest-release): New procedures.
  (%hackage-updater): New variable.
* guix/scripts/refresh.scm (%updaters): Add it.
* doc/guix.texi (Invoking guix refresh): Mention it.

environment: Set a default value for PS1.

* guix/scripts/environment.scm (launch-environment/container): Set PS1
  during container initialization.

guix system: Warn against missing 'guix pull'.

Suggested by Leo Famulari and others.

* guix/scripts/system.scm (maybe-suggest-running-guix-pull): New
procedure.
(perform-action): Call it when ACTION is 'reconfigure.

environment: Properly handle SIGINT.

Switching to execlp means that the process spawned in a container is PID
1, which obsoleted one of the 'guix environment --container' tests
because the init process can't be killed in the usual manner.

* guix/scripts/environment.scm (launch-environment/fork): New procedure.
(launch-environment): Switch from system* to execlp.  Add handler for
SIGINT.
(guix-environment): Use launch-environment/fork.
* tests/guix-environment-container.sh: Replace abnormal exit test with
one that works now that the spawned process is PID 1.

environment: container: Create dummy home directory and /etc/passwd.

* guix/scripts/environment.scm (launch-environment/container): Change
$HOME to the current user's home directory instead of
/homeless-shelter.  Create a dummy /etc/passwd with a single entry for
the current user.
* doc/guix.texi ("invoking guix environment"): Add a note about the
dummy home directory and /etc/passwd.

guix build: '--with-source' correctly matches versioned file names.

* guix/scripts/build.scm: Use the right 'package-name->name+version'
procedure.  Fixes a regression introduced in
1b846da8c372bee78851439fd9e72b2499115e5a.
* tests/scripts-build.scm ("options->transformation, with-source, with
version"): New test.

substitute: Gracefully handle TLS errors.

* guix/scripts/substitute.scm (with-networking): Use 'match-lambda*' and
add case for 'gnutls-error'.

substitute: Do not leak file descriptors for TLS connections.

Partially fixes <http://bugs.gnu.org/20145>.

* guix/scripts/substitute.scm (fetch, download-cache-info):
(http-multiple-get, fetch-narinfos, progress-report-port): Use
'close-connection' instead of 'close-port'.

substitute: Cache transient HTTP errors for 10mn.

* guix/scripts/substitute.scm (fetch-narinfos)[handle-narinfo-response]:
Cache transient errors for 10mn.
(%narinfo-transient-error-ttl): New variable.