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>

Author: sunshineco

t/chainlint.sed

@@ -157,6 +157,7 @@ s/.*\n//
 /^[^']*'[^']*$/{
 	/"[^'"]*'[^'"]*"/!bsqstring
 }
+:folded
 # here-doc -- swallow it
 /<<[ 	]*[-\\']*[A-Za-z0-9_]/bheredoc
 # comment or empty line -- discard since final non-comment, non-empty line
@@ -255,15 +256,15 @@ s/"//g
 N
 s/\n//
 /"/!bdqstring
-bcheckchain
+bfolded
 
 # found multi-line single-quoted string '...\n...' -- slurp until end of string
 :sqstring
 s/'//g
 N
 s/\n//
 /'/!bsqstring
-bcheckchain
+bfolded
 
 # found here-doc -- swallow it to avoid false hits within its body (but keep
 # the command to which it was attached)
@@ -278,7 +279,7 @@ N
 }
 s/^<[^>]*>//
 s/\n.*$//
-bcheckchain
+bfolded
 
 # found "case ... in" -- pass through untouched
 :case

t/chainlint/here-doc-close-subshell.expect

@@ -0,0 +1,2 @@
+(
+>	cat)

t/chainlint/here-doc-close-subshell.test

@@ -0,0 +1,5 @@
+(
+# LINT: line contains here-doc and closes nested subshell
+	cat <<-\INPUT)
+	fizz
+	INPUT

t/chainlint/here-doc-multi-line-command-subst.expect

@@ -0,0 +1,5 @@
+(
+	x=$(bobble &&
+?!AMP?!>>		wiffle)
+	echo $x
+>)

t/chainlint/here-doc-multi-line-command-subst.test

@@ -0,0 +1,9 @@
+(
+# LINT: line contains here-doc and opens multi-line $(...)
+	x=$(bobble <<-\END &&
+		fossil
+		vegetable
+		END
+		wiffle)
+	echo $x
+)

t/chainlint/here-doc-multi-line-string.expect

@@ -0,0 +1,4 @@
+(
+?!AMP?!	cat && echo multi-line	string"
+	bap
+>)

t/chainlint/here-doc-multi-line-string.test

@@ -0,0 +1,8 @@
+(
+# LINT: line contains here-doc and opens multi-line string
+	cat <<-\TXT && echo "multi-line
+	string"
+	fizzle
+	TXT
+	bap
+)