BF: replace show-ref with rev-parse --verify for determining current treeish location

git show-ref -s HEAD  has shown to not work in all scenarios
and git rev-parse --help provides this as an ultimate example:

         ·   Print the object name of the current commit:

               $ git rev-parse --verify HEAD

Include CHANGES.rst into the source distribution

--HG--
extra : transplant_source : %1CI-%A6a%F0%97%A1%AF9%22%C1%03%D7%0C%84%A3%DE%CBc

--HG--
extra : transplant_source : %A6%DC%F6%80lF%5B%82W%E2%86%F9%8A%B9%FF%0FR%D1%E2H

delete more redundant code when encountering constant bool conditions inside of generator expressions

--HG--
extra : transplant_source : ac%24%C9%A2%BBI%5B%E9/%3A%0F%15%FCE%DAQ%C1%E5%81

Originally fixed in 6cc61605, but a regression was later introduced in
519a19a9.

--HG--
extra : transplant_source : e%B0%AA%A0O%D0%06%1F%90%17%9C%0B%B3KN%84%17%E5%19%81

beginning with python3.3 it is different than the general include
directory on debian based systems

--HG--
extra : transplant_source : V%7D%E3%8D%7D%2A%B5%10%D0/D%95%17n%D3z%3Bt2%27

Updated cy break examples so they are more clear. 

--HG--
extra : transplant_source : %FA%95%96M2%1A%D7%40%7B%24%BA%95%99%86%D5t%8F%19%C6%09

This order looks more logical, easier to read.

--HG--
extra : transplant_source : N%A1%DE%08%B0%D9%8B%24%91%2B%29%F0%E9%20%ACY%0EQ%60F

Fixed a code example which had been indented with 2 spaces.

--HG--
extra : transplant_source : %C2%2A8%18%CE%18%87f%BD%E5%0D%5D%90%BA%A0%40%3B%FA%B3%A6

- fixed wrong references (The file on the left (right) -> actual file name)
- divided an example snippet of three files into separate files

--HG--
extra : transplant_source : N0%87%F3%B0%B3W%C5%D6%B93%01T%AB%14%E0%CF%A7%B79

--HG--
extra : transplant_source : %04%AD%9D%8Dy%E4%7F%D04ib%0E%90%DB%D48%C3%88%19g

Originally reported in Debian http://bugs.debian.org/cgi-bin/bugreport.cgi\?bug\=692313
Lead to crash with python-dbg:

  python-dbg: ../Modules/gcmodule.c:366: visit_decref: Assertion 'gc->gc.gc_refs != 0' failed

--HG--
extra : transplant_source : D%E7%E2%8D%C4i%B7%08%F4%83%08sQ%84%27%3E%F3%17%AB%24

--HG--
extra : transplant_source : %88%DC%06k%08%83%3C%E2%17%A5%A24%3E%BC%0Au%92%5DEK

raise overflow error in Py3.3+ when non-BMP Unicode characters are coerced into a short Py_UNICODE value

--HG--
extra : transplant_source : %D3%96%7C%F9%3F%AE%1AA%8C%B9%0E%918%FB%27%F4%CB%E7u-

--HG--
extra : transplant_source : %7C%3E%C7x%E7%A8s%CEF%B5%90%C5%DC%AD%CD%5E%1Fg%F9%7E

--HG--
extra : transplant_source : %CC%EC%23%19%11%1A%22%FB%5C-%18%AD%0D%FC%24L%BD%81%91%FF

--HG--
extra : transplant_source : %08%F6%88rE%C7%F5%CD.%9Ad%244m%0Cw%8C%25g%C0

--HG--
extra : transplant_source : %01%22lN%B0%1D%B9h%AC%2B4%E1F%7FQ%15%E6%F3%F1%9F

--HG--
extra : transplant_source : 81Y%F6%E5%B8%BF%F4%D9%97%85%93%16%9B%A5E%B2%FD%AE%5C

--HG--
extra : transplant_source : %A1/-i%8Cd%C3%DBCy%19%7C%19%87%B9%C5%60%B9P%F5

--HG--
extra : transplant_source : %D5%C52%5C7%CD%85%8F%3D7%9C%27%C6%8AGb%DBX%AEe