Update documentation for spack md5

lib/spack/docs/packaging_guide.rst

@@ -467,14 +467,25 @@ to use based on the hash length.
 ``spack md5``
 ^^^^^^^^^^^^^^^^^^^^^^
 
-If you have a single file to checksum, you can use the ``spack md5``
-command to do it.  Here's how you might download an archive and get a
-checksum for it:
+If you have one or more files to checksum, you can use the ``spack md5``
+command to do it:
 
 .. code-block:: sh
 
-   $ curl -O http://exmaple.com/foo-8.2.1.tar.gz'
-   $ spack md5 foo-8.2.1.tar.gz
+   $ spack md5 foo-8.2.1.tar.gz foo-8.2.2.tar.gz
+   ==> 2 MD5 checksums:
+   4136d7b4c04df68b686570afa26988ac  foo-8.2.1.tar.gz
+   1586b70a49dfe05da5fcc29ef239dce0  foo-8.2.2.tar.gz
+
+``spack md5`` also accepts one or more URLs and automatically downloads
+the files for you:
+
+.. code-block:: sh
+
+   $ spack md5 http://example.com/foo-8.2.1.tar.gz
+   ==> Trying to fetch from http://example.com/foo-8.2.1.tar.gz
+   ######################################################################## 100.0%
+   ==> 1 MD5 checksum:
    4136d7b4c04df68b686570afa26988ac  foo-8.2.1.tar.gz
 
 Doing this for lots of files, or whenever a new package version is

lib/spack/spack/cmd/md5.py

@@ -36,7 +36,7 @@
 def setup_parser(subparser):
     setup_parser.parser = subparser
     subparser.add_argument('files', nargs=argparse.REMAINDER,
-                           help="Files to checksum.")
+                           help="Files/urls to checksum.")
 
 
 def compute_md5_checksum(url):
@@ -67,6 +67,7 @@ def md5(parser, args):
             tty.warn("%s" % e)
 
     # Dump the MD5s at last without interleaving them with downloads
-    tty.msg("%d MD5 checksums:" % len(results))
+    checksum = 'checksum' if len(results) == 1 else 'checksums'
+    tty.msg("%d MD5 %s:" % (len(results), checksum))
     for checksum, url in results:
         print "%s  %s" % (checksum, url)