chainlint: match arbitrary here-docs tags rather than hard-coded names

chainlint.sed swallows top-level here-docs to avoid being fooled by
content which might look like start-of-subshell. It likewise swallows
here-docs in subshells to avoid marking content lines as breaking the
&&-chain, and to avoid being fooled by content which might look like
end-of-subshell, start-of-nested-subshell, or other specially-recognized
constructs.

At the time of implementation, it was believed that it was not possible
to support arbitrary here-doc tag names since 'sed' provides no way to
stash the opening tag name in a variable for later comparison against a
line signaling end-of-here-doc. Consequently, tag names are hard-coded,
with "EOF" being the only tag recognized at the top-level, and only
"EOF", "EOT", and "INPUT_END" being recognized within subshells. Also,
special care was taken to avoid being confused by here-docs nested
within other here-docs.

In practice, this limited number of hard-coded tag names has been "good
enough" for the 13000+ existing Git test, despite many of those tests
using tags other than the recognized ones, since the bodies of those
here-docs do not contain content which would fool the linter.
Nevertheless, the situation is not ideal since someone writing new
tests, and choosing a name not in the "blessed" set could potentially
trigger a false-positive.

To address this shortcoming, upgrade chainlint.sed to handle arbitrary
here-doc tag names, both at the top-level and within subshells.

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

6 files changed, 33 insertions, 0 deletions

diff --git a/t/chainlint/here-doc.expect b/t/chainlint/here-doc.expect
index 2328fe7753..33bc3cc0b4 100644
--- a/t/chainlint/here-doc.expect
+++ b/t/chainlint/here-doc.expect
@@ -1,3 +1,5 @@
 boodle wobba        gorgo snoot        wafta snurb &&
 
+cat >foo &&
+
 horticulture
diff --git a/t/chainlint/here-doc.test b/t/chainlint/here-doc.test
index bd36f6e1d3..8986eefe74 100644
--- a/t/chainlint/here-doc.test
+++ b/t/chainlint/here-doc.test
@@ -7,6 +7,13 @@ quoth the raven,
 nevermore...
 EOF
 
+# LINT: swallow here-doc with arbitrary tag
+cat <<-Arbitrary_Tag_42 >foo &&
+snoz
+boz
+woz
+Arbitrary_Tag_42
+
 # LINT: swallow here-doc (EOF is last line of test)
 horticulture <<\EOF
 gomez
diff --git a/t/chainlint/nested-here-doc.expect b/t/chainlint/nested-here-doc.expect
index 559301e005..0c9ef1cfc6 100644
--- a/t/chainlint/nested-here-doc.expect
+++ b/t/chainlint/nested-here-doc.expect
@@ -1,3 +1,5 @@
+cat >foop &&
+
 (
 	cat &&
 ?!AMP?!	cat
diff --git a/t/chainlint/nested-here-doc.test b/t/chainlint/nested-here-doc.test
index 027e0bb3ff..f35404bf0f 100644
--- a/t/chainlint/nested-here-doc.test
+++ b/t/chainlint/nested-here-doc.test
@@ -1,3 +1,13 @@
+# LINT: inner "EOF" not misintrepreted as closing ARBITRARY here-doc
+cat <<ARBITRARY >foop &&
+naddle
+fub <<EOF
+	nozzle
+	noodle
+EOF
+formp
+ARBITRARY
+
 (
 # LINT: inner "EOF" not misintrepreted as closing INPUT_END here-doc
 	cat <<-\INPUT_END &&
diff --git a/t/chainlint/subshell-here-doc.expect b/t/chainlint/subshell-here-doc.expect
index 19d5aff233..7c2da63bc7 100644
--- a/t/chainlint/subshell-here-doc.expect
+++ b/t/chainlint/subshell-here-doc.expect
@@ -2,4 +2,8 @@
 	echo wobba 	       gorgo snoot 	       wafta snurb &&
 ?!AMP?!	cat >bip
 	echo >bop
+>) &&
+(
+	cat >bup &&
+	meep
 >)
diff --git a/t/chainlint/subshell-here-doc.test b/t/chainlint/subshell-here-doc.test
index 9c3564c247..05139af0b5 100644
--- a/t/chainlint/subshell-here-doc.test
+++ b/t/chainlint/subshell-here-doc.test
@@ -20,4 +20,12 @@
 	wednesday
 	pugsly
 	EOF
+) &&
+(
+# LINT: swallow here-doc with arbitrary tag
+	cat <<-\ARBITRARY >bup &&
+	glink
+	FIZZ
+	ARBITRARY
+	meep
 )