merge: add some useful documentation

encoding: backport paranoid escaping from templatefilters.jsonescape() This was introduced by 55c763926a28. It is required to embed JSON data in HTML page. Convince yourself here: http://escape.alf.nu/1

encoding: add option to escape non-ascii characters in JSON This is necessary for hgweb to embed JSON data in HTML. JSON data must be able to be embedded in non-UTF-8 HTML page so long as the page encoding is compatible with ASCII. According to RFC 7159, non-BMP character is represented as UTF-16 surrogate pair. This function first splits an input string into an array of UTF-16 code points. https://tools.ietf.org/html/rfc7159.html#section-7

encoding: initialize jsonmap when module is loaded This makes jsonescape() a thread-safe function, which is necessary for hgweb. The initialization stuff isn't that slow: $ python -m timeit -n1000 -s 'from mercurial import encoding as x' 'reload(x)' original: 1000 loops, best of 3: 158 usec per loop this patch: 1000 loops, best of 3: 214 usec per loop compared to loading the commands module: $ python -m timeit -n1000 -s 'from mercurial import commands as x' 'reload(x)' 1000 loops, best of 3: 1.11 msec per loop

encoding: change jsonmap to a list indexed by code point This is slightly faster and convenient to implement a paranoid escaping. $ python -m timeit \ -s 'from mercurial import encoding; data = str(bytearray(xrange(128)))' \ 'encoding.jsonescape(data)' original: 100000 loops, best of 3: 15.1 usec per loop this patch: 100000 loops, best of 3: 13.7 usec per loop

update: change default destination to tipmost descendant (issue4673) (BC) Bare 'hg update' now brings you to the tipmost descendant (on the same branch). Leaving the user on the same topological branch. The previous behavior, updating to the tipmost changeset on the same branch could lead to jump from a topological branch to another. This was confusing and impractical. As the only conceivable reason for the old behavior have been address by the recently introduce message about other heads, we can "safely" change this behavior All test changes have been reviewed and seen a valid consequences.