git.c: ignore pager.* when launching builtin as dashed external

When running, e.g., `git -c alias.bar=foo bar`, we expand the alias and
execute `git-foo` as a dashed external. This is true even if git foo is
a builtin. That is on purpose, and is motivated in a comment which was
added in commit 441981bc ("git: simplify environment save/restore
logic", 2016-01-26).

Shortly before we launch a dashed external, and unless we have already
found out whether we should use a pager, we check `pager.foo`. This was
added in commit 92058e4d ("support pager.* for external commands",
2011-08-18). If the dashed external is a builtin, this does not match
that commit's intention and is arguably wrong, since it would be cleaner
if we let the "dashed external builtin" handle `pager.foo`.

This has not mattered in practice, but a recent patch taught `git-tag`
to ignore `pager.tag` under certain circumstances. But, when started
using an alias, it doesn't get the chance to do so, as outlined above.
That recent patch added a test to document this breakage.

Do not check `pager.foo` before launching a builtin as a dashed
external, i.e., if we recognize the name of the external as a builtin.
Change the test to use `test_expect_success`.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git.c

@@ -559,7 +559,7 @@ static void execv_dashed_external(const char **argv)
 	if (get_super_prefix())
 		die("%s doesn't support --super-prefix", argv[0]);
 
-	if (use_pager == -1)
+	if (use_pager == -1 && !is_builtin(argv[0]))
 		use_pager = check_pager_config(argv[0]);
 	commit_pager_choice();
 

t/t7006-pager.sh

@@ -201,7 +201,7 @@ test_expect_success TTY 'git tag -a respects --paginate' '
 	test -e paginated.out
 '
 
-test_expect_failure TTY 'git tag as alias ignores pager.tag with -a' '
+test_expect_success TTY 'git tag as alias ignores pager.tag with -a' '
 	test_when_finished "git tag -d newtag" &&
 	rm -f paginated.out &&
 	test_terminal git -c pager.tag -c alias.t=tag t -am message newtag &&