largefiles: don't process merge actions at all when overwriting

--HG--
branch : stable
largefiles: remove extra check for file to get - it _is_ by definition in p2

--HG--
branch : stable
largefiles: don't prompt for normal/largefile changes when doing plain updates

We used to get like:

  $ hg up -r 2
  foo has been turned into a normal file
  keep as (l)argefile or use (n)ormal file? l
  getting changed largefiles
  0 largefiles updated, 0 removed
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ cat foo
  cat: foo: No such file or directory
  [1]

- which both asked the wrong question and did the wrong thing.

Instead, skip this conflict resolution when the local conflicting file has been
scheduled for removal and there thus is no conflict.

--HG--
branch : stable
rebase: refactor and rename checkexternal - it is a getter more than a setter

--HG--
branch : stable
rebase: improve error message for more than one external parent

--HG--
branch : stable
hgweb: add missing semicolon

--HG--
branch : stable
doc: end line preceding command line example with double colon

--HG--
branch : stable
doc: use double quotation mark to quote arguments in examples for Windows users

On Windows, only double quotation mark can quote command line
arguments.

So, this patch uses double quotation mark to quote command line
arguments in all examples of online help document.

--HG--
branch : stable
doc: put text into header of 1st column in table to generate page correctly

>From the table without header text of 1st column, docutils generates
the table with fully empty header row.

--HG--
branch : stable