* tests/guix-archive.sh, tests/guix-build-branch.sh, tests/guix-build.sh,
tests/guix-daemon.sh, tests/guix-download.sh, tests/guix-environment.sh,
tests/guix-gc.sh, tests/guix-git-authenticate.sh, tests/guix-graph.sh,
tests/guix-hash.sh, tests/guix-lint.sh, tests/guix-pack-relocatable.sh,
tests/guix-pack.sh, tests/guix-package-aliases.sh, tests/guix-package-net.sh,
tests/guix-package.sh: Use the shell '!' keyword to negate command exit status
in place of 'if ...; then false; else true; fi'
* guix/scripts/hash.scm (show-help): Add --recursive.
(%options): Likewise.
(guix-hash)[file-hash]: New procedure. Honor --recursive.
Use it.
* guix/nar.scm (write-file): Add missing field to the &nar-error
condition raised upon unsupported file type; change its message to be
more descriptive.
* tests/guix-hash.sh: Add tests with -r.
* doc/guix.texi (Invoking guix hash): Document --recursive.
* guix/scripts/hash.scm (guix-hash)[eof->null]: New procedure.
Use it to convert the EOF object to the empty bytevector.
* tests/guix-hash.sh: New file.
* Makefile.am (SH_TESTS): Add it.