mercurial: implement import hook for handling C/Python modules There are a handful of modules that have both pure Python and C extension implementations. Currently, setup.py copies files from mercurial/pure/*.py to mercurial/ during the install process if C extensions are not available. This way, "import mercurial.X" will work whether C extensions are available or not. This approach has a few drawbacks. First, there aren't run-time checks verifying the C extensions are loaded when they should be. This could lead to accidental use of the slower pure Python modules. Second, the C extensions aren't compatible with PyPy and running Mercurial with PyPy requires installing Mercurial - you can't run ./hg from a source checkout. This makes developing while running PyPy somewhat difficult. This patch implements a PEP-302 import hook for finding and loading the modules with both C and Python implementations. When a module with dual implementations is requested for import, its import is handled by our import hook. The importer has a mechanism that controls what types of modules we allow to load. We call this loading behavior the "module load policy." There are 3 settings: * Only load C extensions * Only load pure Python * Try to load C and fall back to Python An environment variable allows overriding this policy at run time. This is mainly useful for developers and for performing actions against the source checkout (such as installing), which require overriding the default (strict) policy about requiring C extensions. The default mode for now is to allow both. This isn't proper and is technically backwards incompatible. However, it is necessary to implement a sane patch series that doesn't break the world during future bisections. The behavior will be corrected in future patch. We choose the main mercurial/__init__.py module for this code out of necessity: in a future world, if the custom module importer isn't registered, we'll fail to find/import certain modules when running from a pure installation. Without the magical import-time side-effects, *any* importer of mercurial.* modules would be required to call a function to register our importer. I'm not a fan of import time side effects and I initially attempted to do this. However, I was foiled by our own test harness, which has numerous `python` invoked scripts that "import mercurial" and fail because the importer isn't registered. Realizing this problem is probably present in random Python scripts that have been written over the years, I decided that sacrificing purity for backwards compatibility is necessary. Plus, if you are programming Python, "import" should probably "just work." It's worth noting that now that we have a custom module loader, it would be possible to hook up demand module proxies at this level instead of replacing __import__. We leave this work for another time, if it's even desired. This patch breaks importing in environments where Mercurial modules are loaded from a zip file (such as py2exe distributions). This will be addressed in a subsequent patch.

changegroup: document manifest linkrev callback some more Martin and I just got super-confused reading some code here, so I think it's time for some more documentation.

changegroup: note during bundle apply if the repo was empty An upcoming change for exchanging treemanifest data will need to update the repository capabilities, which we should only do if the repository was empty before we started applying this changegroup. In the future we will probably need a strategy for upgrading to treemanifest in requires during a pull (I'm assuming at some point we'll make it possible to have a flag day to enable treemanifests on an existing history.)

histedit: improve missing rule suggestion include actual suggested text

graphlog: make node symbol templatable by ui.graphnodetemplate option New ui.graphnodetemplate option allows us to colorize a node symbol by phase or branch, [ui] graphnodetemplate = {label('graphnode.{phase}', graphnode)} [color] graphnode.draft = yellow bold or use a variety of unicode emoji characters, and so on. (You'll need less-481 to display non-BMP unicode character.) [ui] graphnodetemplate = {ifeq(obsolete, 'stable', graphnode, '\xf0\x9f\x92\xa9')}

templatekw: avoid slow creation of changectx objects in showgraphnode() This mitigates the minor perf regression introduced by the previous patch. % hg log -G -R mozilla-central -l10000 --time > /dev/null (original) real 2.200 secs (previous) real 2.590 secs (this) real 2.280 secs

graphlog: extract "graphnode" template keyword that represents node symbol This provides a default node symbol. Tests will be added later. "showparents" variable is renamed to "wpnodes" to avoid confusion with the existing showparents() function.

graphlog: move creation of workingdir-parent nodes to displaygraph() Future patches will make a node symbol templatable. Because arguments of a templatekw function are repo and ctx, "showparents" list will have to be built from a repo object by that function.

builddeb: read default distribution and codename from lsb_release This makes `make deb` place packages into a more appropriately named directory instead of just "debian-unknown".

builddeb: remove unused --debbuilddir option Looks like it was never used and after 7f49efcaa9b4 it can be removed.