tests: merging bookmarked heads 45b5eb2941d0 fixed an error that occured when heads being merged were both inactive bookmarks. Add a test for that case.

merge with stable

debuginstall: show directory for Python lib Example new output on Windows: $ hg debuginstall checking encoding (cp1252)... checking Python lib (C:\Users\adi\hgrepos\hg-main\hg-python\lib)... checking installed modules (C:\Users\adi\hgrepos\hg-main\mercurial)... checking templates (C:\Users\adi\hgrepos\hg-main\mercurial\templates)... checking commit editor... C:\Program Files (x86)\Notepad++\notepad++.exe checking username... no problems detected on Linux: adi@kork-ubuntu64:~/hgrepos/hg-main$ ./hg debuginstall checking encoding (UTF-8)... checking Python lib (/usr/lib/python2.7)... checking installed modules (/home/adi/hgrepos/hg-main/mercurial)... checking templates (/home/adi/hgrepos/hg-main/mercurial/templates)... checking commit editor... checking username... no problems detected

util: replace util.nulldev with os.devnull Python since 2.4 has supported os.devnull so having util.nulldev is unnecessary.