bookmarks: calculate visibility exceptions only once

In the loop "for mark in names", the rev is same in each iteration, so it does
not makes sense to call unhidehashlikerevs multiple times. Thanks to Yuya for
spotting this.

mercurial/bookmarks.py

@@ -830,7 +830,12 b' def addbookmarks(repo, tr, names, rev=No'
     cur = repo.changectx('.').node()
     newact = None
     changes = []
-    hiddenrevs = set()
+    hiddenrev = None
+
+    # unhide revs if any
+    if rev:
+        repo = scmutil.unhidehashlikerevs(repo, [rev], 'nowarn')
+
     for mark in names:
         mark = checkformat(repo, mark)
         if newact is None:
@@ -840,17 +845,16 b' def addbookmarks(repo, tr, names, rev=No'
             return
         tgt = cur
         if rev:
-            repo = scmutil.unhidehashlikerevs(repo, [rev], 'nowarn')
             ctx = scmutil.revsingle(repo, rev)
             if ctx.hidden():
-                hiddenrevs.add(ctx.hex()[:12])
+                hiddenrev = ctx.hex()[:12]
             tgt = ctx.node()
         for bm in marks.checkconflict(mark, force, tgt):
             changes.append((bm, None))
         changes.append((mark, tgt))
-    if hiddenrevs:
-        repo.ui.warn(_("bookmarking hidden changeset %s\n") %
-                     ', '.join(hiddenrevs))
+
+    if hiddenrev:
+        repo.ui.warn(_("bookmarking hidden changeset %s\n") % hiddenrev)
     marks.applychanges(repo, tr, changes)
     if not inactive and cur == marks[newact] and not rev:
         activate(repo, newact)