Allow to specify the ExecContext in a call to run_cmd(). This effectively makes run_cmd() an thin wrapper around ExecContext.run(), which is what's going to be used in the future. The wrapper is for backwards-compatibility.
The code below lib.distro, as left behind by the previous commit, is geared towards being directly used as a command-line API. This commit introduces the abstract base class Distro, a proxy for distribution-specific interactions. The proxy abstracts distro specifics into an API with proper method prototypes, not argparse.Namespace contents, and can thus be more easily driven by arbitrary code.
The Distro class is initialized with a member variable of type ExecContext, another new class introduced by this commit. It is designed to abstract the communication channel to the distribution instance. Currently only one specialization exists, Local, which interacts with the distribution and root file system it is running in, but is planned to be subclassed to support interaction via SSH, serial, chroot, or chains thereof.
Functions abstracting the distribution are not only needed in the context of the distro subcommand, but also by other code, so make the bulk of the code abstracting the distribution available in some place more universally useful than below cmds.distro.
This commit leaves the source files mostly unchanged. They are only patched to fix import paths, so that functionality is preserved. Refactoring the code from command-line API to library API will be done by the next commit.
jw-pkg distro dup got hung in a chroot environment. strace shows that write(2) into a pipe is the hanging syscall, with the write buffer hinting at zypper dup output.
I strongly suspect that run_cmd() tries to write stdout into the pipe which read_stream() fails to empty. So, make read_stream() more resilient by using read(4096) instead of readline(), which I suspect to be prone to hang on overlong lines.
--fix-broken is added to apt-get options in non-interactive mode, but seems to work only with apt-get install, not with apt-get update. Don't add it at all for now.
run_cmd() with cmd_input == mode:interactive and verbose == true logs output too often. First, __log() is called, then pty.spawn() writes everything it reads from the PTY master to the terminal.
The fix it to not call __log() from _read() for the PTY reader.
Replace all_installed_packages() by query_packages(). The function takes an optional list of packages to be queried. If it's empty, a list of all installed packages are returned.
Add --download-only to the options of jw-pkg.py distro dup, which makes the command only download packages from the repositories without installing them.
Add the command distro.CmdRebootRequired, adding support for "distro reboot-required". The command exits with status code 1 if a reboot is required and 0 otherwise.
Most run_xxx() return stdout and stderr. There's no way, really, for the caller to get hold of the exit code of the spawned executable. It can pass throw=true, catch, and assume a non-zero exit status. But that's not semantically clean, since the spawned function can well be a test function which is expected to return a non-zero status code, and the caller might be interested in what code that was, exactly.
The clearest way to solve this is to return the exit code as well. This commit does that.
