tests/test-run-tests.t

workingctx: eliminate remove function

Inlining it into it's last remaining call place in cmdutil.copy.

Note that cmdutil.copy is called with the wlock already held, so no additional
locking is needed to call util.unlinkpath.

We do not need to wrap the util.unlinkpath call into a try block, because
at that point we already know whether abssrc exists or not -- thanks to the
preceding util.copyfile call. Adding a new local 'srcexists' in cmdutil.copy
for that purpose.

Simple commands:

  $ echo foo
  foo
  $ printf 'oh no'
  oh no (no-eol)
  $ printf 'bar\nbaz\n' | cat
  bar
  baz

Multi-line command:

  $ foo() {
  >     echo bar
  > }
  $ foo
  bar

Regular expressions:

  $ echo foobarbaz
  foobar.* (re)
  $ echo barbazquux
  .*quux.* (re)

Globs:

  $ printf '* \\foobarbaz {10}\n'
  \* \\fo?bar* {10} (glob)

Literal match ending in " (re)":

  $ echo 'foo (re)'
  foo (re)

Exit code:

  $ (exit 1) 
  [1]