help: document sharing of revlog header with revision 0 The previous docs were incorrect about there being a discrete header on revlogs.

mpatch: move collect() to module level This helps the code read a little more clearly.

mpatch: un-nest the move() method This helps the code read a little more clearly.

mpatch: move pull() method to top level There was no need for this to be nested.

chgserver: use old ui.system if fout is not stdout or needs to be captured Before this patch, chgui will override the system method, forwarding every process execution to the client so sessions and process groups can work as expected. But the chg client will just use stdout, if ui.fout is not stdout or if the output is set to be captured to safe._buffers, the client will not behave correctly. This can happen especially with code prepending "remote:". For example, bundle2 uses ui.pushbuffer, and sshpeer sets fout to ferr. We may have trouble with interactive commands in the fout set to ferr case but if it really bites us, we can always send file descriptors to the client. This patch adds a check to detect the above situations and fallback to the old ui.system if so. It will make chg happy with test-bundle2-exchange.t, test-phases-exchange.t, test-ssh-bundle1.t and test-ssh.t.

node: use byte literals to construct nullid and wdirid Python 3's hex() insists on operating on bytes. This patch gives it what it wants. '' and b'' in Python 2 are equivalent, so this has no impact on Python 2.

tests: try to import modules with Python 3 All of mercurial.* is now using absolute_import. Most of mercurial.* is able to ast parse with Python 3. The next big hurdle is being able to import modules using Python 3. This patch adds testing of hgext.* and mercurial.* module imports in Python 3. As the new test output shows, most modules can't import under Python 3. However, many of the failures are due to a common problem in a highly imported module (e.g. the bytes vs str issue in node.py).

tests: perform an ast parse with Python 3 Previously, test-check-py3-compat.t parsed Python files with Python 2 and looked for known patterns that are incompatible with Python 3. Now that we have a mechanism for invoking Python 3 interpreters from tests, we can expand check-py3-compat.py and its corresponding .t test to perform an additional AST parse using Python 3. As the test output shows, we identify a number of new parse failures on Python 3. There are some redundant warnings for missing parentheses for the print function. Given the recent influx of patches around fixing these, the redundancy shouldn't last for too long.