doc: Distinguish the "nar bundle" format from "nar".

* doc/guix.texi (Invoking guix archive): Introduce the term "nar bundle"
and clarify what the output of "guix archive --export" really is.
* guix/nar.scm (restore-one-item, restore-file-set): Use the term "nar
bundle" in docstrings.

2 files changed, 19 insertions, 8 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index bad2d36e42..db2013c16b 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -4990,7 +4990,13 @@ what you should use in this case (@pxref{Invoking guix copy}).
 
 @cindex nar, archive format
 @cindex normalized archive (nar)
-Archives are stored in the ``normalized archive'' or ``nar'' format, which is
+@cindex nar bundle, archive format
+Each store item is written in the @dfn{normalized archive} or @dfn{nar}
+format (described below), and the output of @command{guix archive
+--export} (and input of @command{guix archive --import}) is a @dfn{nar
+bundle}.
+
+The nar format is
 comparable in spirit to `tar', but with differences
 that make it more appropriate for our purposes.  First, rather than
 recording all Unix metadata for each file, the nar format only mentions
@@ -5000,6 +5006,10 @@ entries are stored always follows the order of file names according to
 the C locale collation order.  This makes archive production fully
 deterministic.
 
+That nar bundle format is essentially the concatenation of zero or more
+nars along with metadata for each store item it contains: its file name,
+references, corresponding derivation, and a digital signature.
+
 When exporting, the daemon digitally signs the contents of the archive,
 and that digital signature is appended.  When importing, the daemon
 verifies the signature and rejects the import in case of an invalid
diff --git a/guix/nar.scm b/guix/nar.scm
index 6bb2ea5b96..a23af2e5de 100644
--- a/guix/nar.scm
+++ b/guix/nar.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014 Mark H Weaver <mhw@netris.org>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -156,7 +156,8 @@ protected from GC."
 (define* (restore-one-item port
                            #:key acl (verify-signature? #t) (lock? #t)
                            (log-port (current-error-port)))
-  "Restore one store item from PORT; return its file name on success."
+  "Restore one store item of a nar bundle read from PORT; return its file name
+on success."
 
   (define (assert-valid-signature signature hash file)
     ;; Bail out if SIGNATURE, which must be a string as produced by
@@ -251,11 +252,11 @@ a signature"))
 (define* (restore-file-set port
                            #:key (verify-signature? #t) (lock? #t)
                            (log-port (current-error-port)))
-  "Restore the file set read from PORT to the store.  The format of the data
-on PORT must be as created by 'export-paths'---i.e., a series of Nar-formatted
-archives with interspersed meta-data joining them together, possibly with a
-digital signature at the end.  Log progress to LOG-PORT.  Return the list of
-files restored.
+  "Restore the file set (\"nar bundle\") read from PORT to the store.  The
+format of the data on PORT must be as created by 'export-paths'---i.e., a
+series of Nar-formatted archives with interspersed meta-data joining them
+together, possibly with a digital signature at the end.  Log progress to
+LOG-PORT.  Return the list of files restored.
 
 When LOCK? is #f, assume locks for the files to be restored are already held.
 This is the case when the daemon calls a build hook.