tag: do not allow tag names to consist solely of whitespace (issue2307)

(simplification and test by mpm)

mercurial/commands.py

@@ -3660,6 +3660,8 b' def tag(ui, repo, name1, *names, **opts)'
     for n in names:
         if n in ['tip', '.', 'null']:
             raise util.Abort(_('the name \'%s\' is reserved') % n)
+        if not n:
+            raise util.Abort(_('tag names cannot consist entirely of whitespace'))
     if opts.get('rev') and opts.get('remove'):
         raise util.Abort(_("--rev and --remove are incompatible"))
     if opts.get('rev'):

tests/test-tag

@@ -7,6 +7,9 b' echo a > a'
 hg add a
 hg commit -m "test" -d "1000000 0"
 hg history
+
+hg tag ' '
+
 hg tag -d "1000000 0" "bleah"
 hg history
 

tests/test-tag.out

@@ -4,6 +4,7 b' user: test'
 date:        Mon Jan 12 13:46:40 1970 +0000
 summary:     test
 
+abort: tag names cannot consist entirely of whitespace
 changeset:   1:3ecf002a1c57
 tag:         tip
 user:        test