Re: [Libguestfs] [PATCH 0/7] copy-in/copy-out: Capture errors from tar subprocess (RHBZ#1267032).

Commits 3c27f3d91e1566854747bbe844186783fc84f3a8 and 1b6f0daa9ae7fcc94e389232d0c397816cda973d added an internal API for running commands asynchronously. It is only used by the copy-in and copy-out APIs. Unfortunately this made the command code very complex: it was almost impossible to redirect stderr to a file, and there were a lot of long-range dependencies through the file. It was also buggy: it set up stderr of the child process pointing pipe, but never read from the pipe, so if the stderr output of the child process was sufficiently large then libguestfs would deadlock (possibly this can be triggered from a malicious filesystem too). This patch series first reverts these commits, then adds a simpler way to run a child process without waiting (modelled on popen()), allows stderr errors to be captured, then reimplements copy-in/copy-out using these new internal APIs. Note that the patch series breaks bisection, but I can't really think of a clearer way to reorganize it that would preserve bisection.