chainlint: let here-doc and multi-line string commence on same line

After swallowing a here-doc, chainlint.sed assumes that no other
processing needs to be done on the line aside from checking for &&-chain
breakage; likewise, after folding a multi-line quoted string. However,
it's conceivable (even if unlikely in practice) that both a here-doc and
a multi-line quoted string might commence on the same line:

    cat <<\EOF && echo "foo
    bar"
    data
    EOF

Support this case by sending the line (after swallowing and folding)
through the normal processing sequence rather than jumping directly to
the check for broken &&-chain.

This change also allows other somewhat pathological cases to be handled,
such as closing a subshell on the same line starting a here-doc:

    (
        cat <<-\INPUT)
        data
        INPUT

or, for instance, opening a multi-line $(...) expression on the same
line starting a here-doc:

    x=$(cat <<-\END &&
        data
        END
        echo "x")

among others.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/t/chainlint/here-doc-multi-line-string.expect b/t/chainlint/here-doc-multi-line-string.expect
new file mode 100644
index 0000000000..1e5b724b9d
--- /dev/null
+++ b/t/chainlint/here-doc-multi-line-string.expect
@@ -0,0 +1,4 @@
+(
+?!AMP?!	cat && echo multi-line	string"
+	bap
+>)