transaction: clear callback instances after usage Prevents double usage and helps reduce reference cycles, which were observed to occur in `hg convert` and other scenarios where there are multiple transactions per process.

lock: clear postrelease hooks list after usage Post release hooks should only be called once. Setting the list to None after usage will prevent accidental usage after they are used. In addition, it is easy for reference cycles to sneak into hook functions. Clearing the hooks after usage helps prevent these cycles.

ui: drop template aliases by HGPLAIN Otherwise, scripting output could be suffered from user aliases.

templater: load and expand aliases by template engine (API) (issue4842) Now template aliases are fully supported in log and formatter templates. As I said before, aliases are not expanded in map files. This avoids possible corruption of our stock styles and web templates. This behavior is undocumented since no map file nor [templates] section are documented at all. Later on, we might want to add [aliases] section to map files if it appears to be useful.

templater: inline compiletemplate() function into engine This allows the template engine to modify parsed tree.

templater: factor out function that creates templater from string template This function will host loading of template aliases. It is not defined at templater, but at formatter, since formatter is the module handling ui stuff in front of templater.

templater: separate function to create templater from map file (API) New frommapfile() function will make it clear when template aliases will be loaded. They should be applied to command arguments and templates in hgrc, but not to map files. Otherwise, our stock styles and web templates (i.e map-file templates) could be modified unintentionally. Future patches will add "aliases" argument to __init__(), but not to frommapfile().

templater: extract function that loads template map file Prepares for API change. See the next patch for details. 'map' variable is renamed to avoid shadowing map() function.