tests: save the original PATH and PYTHONPATH variables When running the tests, define ORIG_PATH and ORIG_PYTHONPATH environment variables that contain the original contents of PATH and PYTHONPATH, before they were modified by run-tests.py This will make it possible for tests to refer to the original contents of these variables if necessary. In particular, this is necessary for invoking the correct version of hg for examining the local repository (the mercurial repository itself, not the temporary test repositories). Various tests examine the local repository to check the file lists and contents of commit messages.

setup: prefer using the system hg to interact with the local repository Add a findhg() function that tries to be smarter about figuring out how to run hg for examining the local repository. It first tries running "hg" from the user's PATH, with the default HGRCPATH settings intact, but with HGPLAIN enabled. This will generally use the same version of mercurial and the same settings used to originally clone the repository, and should have a higher chance of working successfully than trying to run the hg script from the local repository. If that fails findhg() falls back to the existing behavior of running the local hg script.

setup: replace runhg() with an hgcommand helper class Replace the runhg() function with an hgcommand helper class. hgcommand has as run() function similar to runhg(), but no longer requires the caller to pass in the exact path to python and the hg script, and the environment settings for invoking hg. For now this diff contains no behavior changes, but in the future this will make it easier for the hgcommand helper class to more intelligently figure out the proper way to invoke hg.

setup: move environment computation into a helper function Add a helper function to compute the environment used for invoking mercurial, rather than doing this computation entirely at global scope. This will make it easier to do some subsequent refactoring.