test-clone.t: check that branch "@" is not automatically checked out

This verifies that c9339efed653 fixes the second problem mentioned in
issue3677.

tests/test-clone.t

@@ -318,8 +318,43 b" Branch 'default' is checked out:"
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     hacked default
   
+Test clone with a branch named "@" (issue3677)
 
-  $ rm -r ua
+  $ hg -R ua branch @
+  marked working directory as branch @
+  (branches are permanent and global, did you want a bookmark?)
+  $ hg -R ua commit -m 'created branch @'
+  $ hg clone ua atbranch
+  updating to branch default
+  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg -R atbranch heads
+  changeset:   16:798b6d97153e
+  branch:      @
+  tag:         tip
+  parent:      12:f21241060d6a
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     created branch @
+  
+  changeset:   15:0aae7cf88f0d
+  branch:      stable
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     another change for branch stable
+  
+  changeset:   12:f21241060d6a
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     hacked default
+  
+  $ hg -R atbranch parents
+  changeset:   12:f21241060d6a
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     hacked default
+  
+
+  $ rm -r ua atbranch
 
 
 Testing #<branch>: