packages: Allow package lookups with version prefixes.

* gnu/packages.scm (find-packages-by-name): Sort MATCHING according to
  'version>?'.  Use 'string-prefix?' instead of 'string=?' to compare
  against VERSION.
* doc/guix.texi (Invoking guix package): Add example and explanation.

1 files changed, 4 insertions, 1 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index ad572365a8..69d65998c5 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -962,7 +962,10 @@ Install the specified @var{package}s.
 
 Each @var{package} may specify either a simple package name, such as
 @code{guile}, or a package name followed by a hyphen and version number,
-such as @code{guile-1.8.8}.  If no version number is specified, the
+such as @code{guile-1.8.8} or simply @code{guile-1.8} (in the latter
+case, the newest version prefixed by @code{1.8} is selected.)
+
+If no version number is specified, the
 newest available version will be selected.  In addition, @var{package}
 may contain a colon, followed by the name of one of the outputs of the
 package, as in @code{gcc:doc} or @code{binutils-2.22:lib}