templater: introduce filter() function to remove empty items from list The primary use case is to filter out "tip" from a list of tags.

templater: fix truth testing of integer 0 taken from a list/dict Broken at f9c426385853. bool(python_value) shouldn't be used here since an integer 0 has to be truthy for backward compatibility.

formatter: look for template symbols from the associated name Otherwise symbolsused() would fail if a named template is specified with -T.

py3: add b'' prefixes in tests/test-obsolete-divergent.t This makes the test pass on Python 3. # skip-blame because just b'' prefixes. Differential Revision: https://phab.mercurial-scm.org/D3832

py3: use stringutil.pprint() to print NoneType Before this patch, when running test-debugcommands.t, we get a TypeError because NoneType can't be converted into bytes. This patch uses stringutil.pprint() to print the ui._colormode. We are now close to getting test-debugcommands.t passing on Python 3. Differential Revision: https://phab.mercurial-scm.org/D3831

rebase: make dry-run return 1 or 0 according to result In dry-run mode, if there is no conflict return 0, if any then return 1 Differential Revision: https://phab.mercurial-scm.org/D3829

relink: use context manager for lock management

censor: use context manager for lock management

templater: remove redundant member variables from templater class We no longer need them since the engine is instantiated in __init__().

templater: resurrect cache of engine instance The engine-level cache was effectively disabled at 48289eafb37d "templater: drop extension point of engine classes (API)" by mistake, which made template rendering quite slow. Spotted by Martin von Zweigbergk.