sh: Allow terminating a heredoc with a terminator at EOF without a newline.

This is sometimes used with eval or old-style command substitution, and most
shells other than ash derivatives allow it.

It can also be used with scripts that violate POSIX's requirement on the
application that they end in a newline (scripts must be text files except
that line length is unlimited).

Example:
v=`cat <<EOF
foo
EOF`
echo $v

This commit does not add support for the similar construct with new-style
command substitution, like
v=$(cat <<EOF
foo
EOF)
This continues to require a newline after the terminator.

1 files changed, 5 insertions, 3 deletions

diff --git a/bin/sh/parser.c b/bin/sh/parser.c
index cc1860df22fd..192769b076c4 100644
--- a/bin/sh/parser.c
+++ b/bin/sh/parser.c
@@ -1513,10 +1513,12 @@ checkend: {
 
 				p = line;
 				for (q = eofmark + 1 ; *q && *p == *q ; p++, q++);
-				if (*p == '\n' && *q == '\0') {
+				if ((*p == '\0' || *p == '\n') && *q == '\0') {
 					c = PEOF;
-					plinno++;
-					needprompt = doprompt;
+					if (*p == '\n') {
+						plinno++;
+						needprompt = doprompt;
+					}
 				} else {
 					pushstring(line, strlen(line), NULL);
 				}