bug#35506: 27.0.50; Emacs hangs while interrupting tramp processes

[John Shahid]

There are two issues I ran into recently while trying to interrupt a
remote process spawned by tramp.  The process in question is terraform
which ahss the following process tree:

  process1 (spawned by tramp)
  ⌞ process2 (child process)
    ⌞ process3 (multiple sub processes)
    ⌞ process4

process1 does not handle signals which causes the interrupts to be
ignored.  Moreover because of the following line in
`tramp-interrupt-process', Emacs ends up busy waiting until the process
exits:

  (with-timeout (1 (ignore))
    (while (tramp-accept-process-output proc))
    ;; Report success.
    proc)

It looks like the first issue can be solved by killing the entire
process group, but I am not sure how safe it is to always do that.  I
will attach a patch that I use locally which seem harmless so far.

The second issue can be solved by not waiting for the process to exit.
This seems to be in line with the contract of `interrupt-process'.  I
will attach a patch to remove the wait.


Note, the following commit is not on master.  This is a local commit
with a bunch of changes that I'm trying to get pushed to master.

In GNU Emacs 27.0.50 (build 22, x86_64-pc-linux-gnu, GTK+ Version 3.24.8)
 of 2019-04-29 built on amun
Repository revision: cf2d0e2e58a683756878c9c7e4dd2066efe6e807
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Arch Linux

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