cleanup: remove useless re-raises of KeyboardInterrupt KeyboardInterrupt is no longer a subclass of Exception since Python 2.5. https://docs.python.org/2/whatsnew/2.5.html#pep-352-exceptions-as-new-style-classes

make: drop deprecated rule to process temporary copy of pure modules Pure modules never be copied to mercurial/ since 511a4384b033.

help: describe about choice of :prompt as a fallback merge tool explicitly "merge-tools" help topic has described that the merge of the file fails if no tool is found to merge binary or symlink, since c77f6276c9e7 (or Mercurial 1.7), which based on (already removed) MergeProgram wiki page. But even at that revision, and of course now, merge of the file doesn't fail automatically for binary/symlink. ":prompt" (or equivalent logic) is used, if there is no appropriate tool configuration for binary/symlink.