Bryan O'Sullivan <bos@serpentine.com> [Mon, 11 Jan 2016 15:25:43 -0800] rev 27703
util: introduce ctxmanager, to avoid nested try/finally blocks
This is similar in spirit to contextlib.nested in Python <= 2.6,
but uses an extra level of indirection to avoid its inability to
clean up if an __enter__ method raises an exception.
Why add this mechanism? It greatly simplifies scoped resource
management, and lets us eliminate several hundred lines of try/finally
blocks. In many of these cases the "finally" is separated from the
"try" by hundreds of lines of code, which makes the connection
between resource acquisition and disposal difficult to follow.
(The preferred mechanism would be the "multi-with" syntax of 2.7+,
but Mercurial can't move to 2.7 for a while.)
Intended use:
>>> with ctxmanager(lambda: file('foo'), lambda: file('bar')) as c:
>>> f1, f2 = c()
This will open both foo and bar when c() is invoked, and will close
both upon exit from the block. If the attempt to open bar raises
an exception, the block will not be entered - but foo will still
be closed.
timeless <timeless@mozdev.org> [Mon, 11 Jan 2016 23:13:34 +0000] rev 27702
hghave: support HGMODULEPOLICY for pure
HGMODULEPOLICY was introduced in 4374d819ccd5
Matt Mackall <mpm@selenic.com> [Mon, 11 Jan 2016 14:27:12 -0600] rev 27701
merge with stable