tests: fix and add lint for non-portable seq

The seq command is not in POSIX, and doesn't exist on
e.g. OpenBSD. We've had the test_seq wrapper since d17cf5f3a3 ("tests:
Introduce test_seq", 2012-08-04), but use of it keeps coming back,
e.g. in the recently added "fetch negotiator" tests being added here.

So let's also add a check to "make test-lint". The regex is aiming to
capture the likes of $(seq ..) and "seq" as a stand-alone command,
without capturing some existing cases where we e.g. have files called
"seq", as \bseq\b would do.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/check-non-portable-shell.pl

@@ -42,6 +42,7 @@ while (<>) {
 	/\btest\s+[^=]*==/ and err '"test a == b" is not portable (use =)';
 	/\bwc -l.*"\s*=/ and err '`"$(wc -l)"` is not portable (use test_line_count)';
 	/\bhead\s+-c\b/ and err 'head -c is not portable (use test_copy_bytes BYTES <file >out)';
+	/(?:\$\(seq|^\s*seq\b)/ and err 'seq is not portable (use test_seq)';
 	/\bexport\s+[A-Za-z0-9_]*=/ and err '"export FOO=bar" is not portable (use FOO=bar && export FOO)';
 	/^\s*([A-Z0-9_]+=(\w+|(["']).*?\3)\s+)+(\w+)/ and exists($func{$4}) and
 		err '"FOO=bar shell_func" assignment extends beyond "shell_func"';

t/t5552-skipping-fetch-negotiator.sh

@@ -46,7 +46,7 @@ test_expect_success 'commits with no parents are sent regardless of skip distanc
 	test_commit -C server to_fetch &&
 
 	git init client &&
-	for i in $(seq 7)
+	for i in $(test_seq 7)
 	do
 		test_commit -C client c$i
 	done &&
@@ -89,7 +89,7 @@ test_expect_success 'when two skips collide, favor the larger one' '
 	test_commit -C server to_fetch &&
 
 	git init client &&
-	for i in $(seq 11)
+	for i in $(test_seq 11)
 	do
 		test_commit -C client c$i
 	done &&
@@ -168,14 +168,14 @@ test_expect_success 'do not send "have" with ancestors of commits that server AC
 	test_commit -C server to_fetch &&
 
 	git init client &&
-	for i in $(seq 8)
+	for i in $(test_seq 8)
 	do
 		git -C client checkout --orphan b$i &&
 		test_commit -C client b$i.c0
 	done &&
-	for j in $(seq 19)
+	for j in $(test_seq 19)
 	do
-		for i in $(seq 8)
+		for i in $(test_seq 8)
 		do
 			git -C client checkout b$i &&
 			test_commit -C client b$i.c$j
@@ -205,7 +205,7 @@ test_expect_success 'do not send "have" with ancestors of commits that server AC
 
 	# fetch-pack should thus not send any more commits in the b1 branch, but
 	# should still send the others (in this test, just check b2).
-	for i in $(seq 0 8)
+	for i in $(test_seq 0 8)
 	do
 		have_not_sent b1.c$i
 	done &&

t/t5703-upload-pack-ref-in-want.sh

@@ -176,7 +176,7 @@ test_expect_success 'setup repos for change-while-negotiating test' '
 		git clone "http://127.0.0.1:$LIB_HTTPD_PORT/smart/repo" "$LOCAL_PRISTINE" &&
 		cd "$LOCAL_PRISTINE" &&
 		git checkout -b side &&
-		for i in $(seq 1 33); do test_commit s$i; done &&
+		for i in $(test_seq 1 33); do test_commit s$i; done &&
 
 		# Add novel commits to upstream
 		git checkout master &&
@@ -289,7 +289,7 @@ test_expect_success 'setup repos for fetching with ref-in-want tests' '
 		git clone "file://$REPO" "$LOCAL_PRISTINE" &&
 		cd "$LOCAL_PRISTINE" &&
 		git checkout -b side &&
-		for i in $(seq 1 33); do test_commit s$i; done &&
+		for i in $(test_seq 1 33); do test_commit s$i; done &&
 
 		# Add novel commits to upstream
 		git checkout master &&