localrepo: use ProgrammingError This is an example usage of ProgrammingError. Let's start migrating RuntimeError to ProgrammingError. The code only runs when devel.all-warnings or devel.check-locks is set, so it does not affect the end-user experience.

error: add ProgrammingError We have requirement to express "this is clearly an error caused by the programmer". The code base uses RuntimeError for that in some places, not ideal. So let's add a formal exception for that.

chgserver: call "load" for new ui objects After d83ca854fa21, we need to call "ui.load" explicitly to load config files.

localrepository: remove None as default value of path argument in __init__() The path variable in localrepository.__init__() has a default value None. So it gives us a option to create an object to localrespository class without path variable. But things break if you try to do so. The second line in the init which will be executed when we try to create a localrepository object will call os.path.expandvars(path) which returns TypeError: argument of type 'NoneType' is not iterable I checked occurrences when it is called and can't find any piece of code which calls it without path variable. Also if something is calling it, its should break.

py3: use pycompat.sysstr() in __import__() __import__() on Python 3 accepts strings which are different from that of Python 2. Used pycompat.sysstr() to get string accordingly.

py3: avoid use of basestring "In this case, result is a source variable of a list to be returned, it shouldn't be unicode. Hence we can use bytes instead of basestring here." -Yuya

py3: use unicodes in __slots__ __slots__ in Python 3 accepts only unicodes and there is no harm using unicodes in __slots__. So just adding u'' is fine. Previous occurences of this problem are treated the same way.

memctx: allow the metadataonlyctx thats reusing the manifest node When we have a lot of files writing a new manifest revision can be expensive. This commit adds a possibility for memctx to reuse a manifest from a different commit. This can be beneficial for commands that are creating metadata changes without any actual files changed like "hg metaedit" in evolve extension. I will send the change for evolve that leverages this once this is accepted.