tests: introduce c-style conditional sections in .t tests
This makes it possible to have conditional sections like:
#if windows
$ echo foo
foo
#else
$ echo bar
bar
#endif
The directives and skipped sections are treated like comments, so don't
interleave them with commands and their output.
The parameters to #if are evaluated while preparing the test by passing them
over to hghave. Requirements can thus be negated with 'no-' prefix, and
multiple requirements must all be true to return true.
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
Return codes before inline python:
$ sh -c 'exit 1'
[1]
Doctest commands:
>>> print 'foo'
foo
$ echo interleaved
interleaved
>>> for c in 'xyz':
... print c
x
y
z
>>> print
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)
Conditional sections based on hghave:
#if fifo no-fifo
$ echo skipped
#else
$ echo tested
tested
#endif
Exit code:
$ (exit 1)
[1]