t4018 (funcname patterns): minor cleanups

t4018 (funcname patterns): minor cleanups

Introduce a test_expect_funcname function to make a diff and apply a
regexp anchored on the left to the function name it writes, avoiding
some repetition.

Omit the space after >, <<, and < operators for consistency with
other scripts.  Quote the <<here document delimiter and $ signs in
quotes so readers don't have to worry about the effect of shell
metacharacters.

Remove some unnecessary blank lines.

Run "git diff" as a separate command instead of as upstream of a pipe
that checks its output, so the exit status can be tested.  In
particular, this way if "git diff" starts segfaulting the test harness
will notice.

Allow "error:" as a synonym for "fatal:" when checking error messages,
since whether a command uses die() or "return error()" is a small
implementation detail.

Anchor some more regexes on the right.

None of the above is very important on its own; the point is just to
make the script a little easier to read and the code less scary to
modify.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>