Use this to remove [path_prefix] highlighting during accept-* widgets.
This causes ": file.tx<CR>" to remove the underline from "file.tx", like
": file.tx<SPACE>" already does.  (Assume 'file.txt' exists.)

It's the widget's caller's responsibility, not ours, to add '--' where due.  If
we do it, two instances of '--' might result.  (I haven't been able to provoke
this problem.)

If this commit causes problems, the cause would be widget-callers that don't
pass '--' although they should.

test failure would not be reflected by the exit code of 'make'.

Setting a shell parameter in the left-hand side of a pipe is not visible to
commands after the pipe, because the left-hand side forks.  (That's true both
in 'sh' used by 'make' and in 'zsh' that runs tests/test-highlighting.zsh, at
least on my system.)  Therefore, move the colorizing hook to where it doesn't
interfere with setting the $something_failed (in tests/test-highlighting.zsh)
and $result (in Makefile) parameters.

Fixes zsh-users/zsh-syntax-highlighting#187.
Adds a test for zsh-users/zsh-syntax-highlighting#204.

Color is only added when "make test"'s stdout is a tty.

preview-smaller.png is derived from preview.png by 50% downscaling.

Prior art: 66c18e6b71

Followup to b2ac98b981.

Fixes zsh-users/zsh-syntax-highlighting#217.

Fixes zsh-users/zsh-syntax-highlighting#218.

Update expectations on the subshell test (which triggered this bug, since it has
a passing test point following a 'todo' test point).

Make the test pass by setting explicitly the global state (existing $HOME) it
depends on.  Test another value of the global state (a non-existing $HOME).

That allows tests to be completely independent of each other, so tests that
change global state — such as modify environment variables, define functions or
aliases, or hash commands — will not affect other tests, without needing an
explicit cleanup step.

This enables testing path-tilde-home with and without $HOME set, which is part
of issue #216.

While at it, convert the test harness to TAP.  This fixes issue #180 by adding
support for "not ok 42 # TODO" output.

This commit assumes that 'grep' supports POSIX-compliant -q and -v flags.

Patch-by: Matthew Martin <phy1729@gmail.com>

Fixes zsh-users/zsh-syntax-highlighting#215.

Based on text by Carsten Hey <carsten@debian.org>.

Follow-up to the last commit.

E: zsh-syntax-highlighting: missing-dep-for-interpreter zsh => zsh | zsh-beta (usr/share/zsh-syntax-highlighting/highlighters/main/main-highlighter.zsh)
W: zsh-syntax-highlighting: executable-not-elf-or-script usr/share/zsh-syntax-highlighting/highlighters/main/main-highlighter.zsh

All these files should be sourced, not executed; and Debian's lintian complains:

W: zsh-syntax-highlighting: script-not-executable usr/share/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh

Currently, this only works in installed trees and exported tarballs; the
parameter is left unset when running directly from a git worktree.

Tested with 'bmake -B'.

Found-by: Carsten Hey