These are another sort of external addon process, and this makes several
things work including shell scripts on windows. And it makes for nicer
error messages when the command is not in the path.
Note that the refactored startExternalAddonProcess used by this
does not use propGitEnv to set git environment variables in the
environment. Unlike startExternalAddonProcessProtocol which does.
This is because it runs in IO and does not have access to that
information. But also, I don't think that P2P.Generic processes need
that.
p2p: Added --enable option, which can be used to enable P2P networks
provided by external commands git-annex-p2p-<netname>
Made git-annex p2p --enable tor behave the same as git-annex enable-tor,
to make tor a bit less of a special case. However, it canot be run as root,
since it cannot take the user id parameter.
This uses a DebugSelector, rather than debug levels, which will allow
for a later option like --debug-from=Process to only
see debuging about running processes.
The module name that contains the thing being debugged is used as the
DebugSelector (in most cases; does not need to be a hard and fast rule).
Debug calls were changed to add that. hslogger did not display
that first parameter to debugM, but the DebugSelector does get
displayed.
Also fastDebug will allow doing debugging in places that are used in
tight loops, with the DebugSelector coming from the Annex Reader
essentially for free. Not done yet.
Make sure to relay any remaining stderr from the process after it has
shut down, rather than closing stderr just before shutdown. This avoids
a situation where the process is still running and tries to write to
stderr, getting a SIGPIPE. And, it ensures that no stderr output is
lost.
This may fix a problem encountered by datalad on windows, where it hangs
during the external special remote shutdown.
Before commit a49d300545, it closed stdin
and stdout, but left stderr open, and never killed the stderr waiter
thread, which presumably exited on its own. For async exception
safety, do need to at make sure that thread gets waited on, as that
commit does, but it introduced this problem.
Note that, the process's stdout is closed before waiting on it. It's too
late for anything it writes to stdout to be processed, and since we're
not going to consume any such writes, this avoids the process getting
blocked writing to stdout due to us not reading what it's buffered. This
does mean that if the process writes to stdout too late, it will get a
SIGPIPE. (This was already the case before the above-mentioned commit.)
In practice, I think only the protocol's ERROR is allowed to be
sent at a point where this could happen.
