mq: eliminate explicit checks for file existence

mq: cleanup of lookup - handling of None is not relevant Patch specifications in mq is passed around as a string or None. None is generally used when no patch has been specified and there thus is nothing to lookup and the calling code should do something else. One code path did however pass None all the way to lookup. That case was handled in lookup, but there was really need for that, it was undocumented, and it used to cause trouble back when patches was specified as integers.

mq: fix corner cases for handling of patch 0 in qselect Most of the code paths in mq would always pass patch specifications as a string. Patches can be specified by their index, but one code path passed that (through pop) to lookup as an integer - all other code paths used a string. Unfortunately pop and lookup (like many other parts of mq) used the boolean value of the patch specification to see if it was None, and they would thus incorrectly handle patch 0 as None. This patch makes the code comply with the actual internal duck typing of patch specifications: patch indices must be encoded as strings. The (now) unused code for partial and thus incorrect handling of indices as integers is removed.

largefiles: cosmetics, whitespace, code style This is mainly about keeping code under the 80-column limit with as few backslashes as possible. I am deliberately not making any logic or behaviour changes here and have restrained myself to a few "peephole" refactorings.

largefiles: more work on cleaning up comments - always say "largefile", not "lfile" - cleanup mangled syntax, hopefully correctly (punctuation: it's your friend!) - wrap to 75 columns (where feasible)

largefiles: improve error reporting - tweak wording of some error messages - use consistent capitalization - always say 'largefile', not 'lfile' - fix I18N problems - only raise Abort for errors the user can do something about

largefiles: improve comments, internal docstrings - fix some ungrammatical/unclear/incorrect comments/docstrings - rewrite some really unclear comments/docstrings - make formatting/style more consistent with the rest of Mercurial (lowercase without period unless it's really multiple sentences) - wrap to 75 columns - always say "largefile(s)", not "lfile(s)" (or "big files") - one space between sentences, not two

largefiles: flush out tests to cover more operations and known cornercases

largefiles: speed up commit by only rewriting standins for modified largefiles

tests: add basic tests for doctest syntax