support pager.* for external commands

Without this patch, any commands that are not builtin would
not respect pager.* config. For example:

  git config pager.stash false
  git stash list

would still use a pager. With this patch, pager.stash now
has an effect. If it is not specified, we will still fall
back to pager.log when we invoke "log" from "stash list".

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git.c

@@ -467,6 +467,8 @@ static void execv_dashed_external(const char **argv)
 	const char *tmp;
 	int status;
 
+	if (use_pager == -1)
+		use_pager = check_pager_config(argv[0]);
 	commit_pager_choice();
 
 	strbuf_addf(&cmd, "git-%s", argv[0]);

t/t7006-pager.sh

@@ -450,4 +450,40 @@ test_expect_success TTY 'command-specific pager overridden by environment' '
 	test_cmp expect actual
 '
 
+test_expect_success 'setup external command' '
+	cat >git-external <<-\EOF &&
+	#!/bin/sh
+	git "$@"
+	EOF
+	chmod +x git-external
+'
+
+test_expect_success TTY 'command-specific pager works for external commands' '
+	sane_unset PAGER GIT_PAGER &&
+	echo "foo:initial" >expect &&
+	>actual &&
+	test_config pager.external "sed s/^/foo:/ >actual" &&
+	test_terminal git --exec-path="`pwd`" external log --format=%s -1 &&
+	test_cmp expect actual
+'
+
+test_expect_success TTY 'sub-commands of externals use their own pager' '
+	sane_unset PAGER GIT_PAGER &&
+	echo "foo:initial" >expect &&
+	>actual &&
+	test_config pager.log "sed s/^/foo:/ >actual" &&
+	test_terminal git --exec-path=. external log --format=%s -1 &&
+	test_cmp expect actual
+'
+
+test_expect_success TTY 'external command pagers override sub-commands' '
+	sane_unset PAGER GIT_PAGER &&
+	>expect &&
+	>actual &&
+	test_config pager.external false &&
+	test_config pager.log "sed s/^/log:/ >actual" &&
+	test_terminal git --exec-path=. external log --format=%s -1 &&
+	test_cmp expect actual
+'
+
 test_done