ref-filter: resurrect "strip" as a synonym to "lstrip"

We forgot that "strip" was introduced at 0571979b ("tag: do not
show ambiguous tag names as "tags/foo"", 2016-01-25) as part of Git
2.8 (and 2.7.1) when we started calling this "lstrip" to make it
easier to explain the new "rstrip" operation.

We shouldn't have renamed the existing one; "lstrip" should have
been a new synonym that means the same thing as "strip".  Scripts
in the wild are surely using the original form already.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/git-for-each-ref.txt

@@ -107,6 +107,8 @@ refname::
 	enough components, the result becomes an empty string if
 	stripping with positive <N>, or it becomes the full refname if
 	stripping with negative <N>.  Neither is an error.
++
+`strip` can be used as a synomym to `lstrip`.
 
 objecttype::
 	The type of the object (`blob`, `tree`, `commit`, `tag`).

ref-filter.c

@@ -112,7 +112,8 @@ static void refname_atom_parser_internal(struct refname_atom *atom,
 		atom->option = R_NORMAL;
 	else if (!strcmp(arg, "short"))
 		atom->option = R_SHORT;
-	else if (skip_prefix(arg, "lstrip=", &arg)) {
+	else if (skip_prefix(arg, "lstrip=", &arg) ||
+		 skip_prefix(arg, "strip=", &arg)) {
 		atom->option = R_LSTRIP;
 		if (strtol_i(arg, 10, &atom->lstrip))
 			die(_("Integer value expected refname:lstrip=%s"), arg);

t/t6300-for-each-ref.sh

@@ -59,18 +59,26 @@ test_atom head refname:rstrip=1 refs/heads
 test_atom head refname:rstrip=2 refs
 test_atom head refname:rstrip=-1 refs
 test_atom head refname:rstrip=-2 refs/heads
+test_atom head refname:strip=1 heads/master
+test_atom head refname:strip=2 master
+test_atom head refname:strip=-1 master
+test_atom head refname:strip=-2 heads/master
 test_atom head upstream refs/remotes/origin/master
 test_atom head upstream:short origin/master
 test_atom head upstream:lstrip=2 origin/master
 test_atom head upstream:lstrip=-2 origin/master
 test_atom head upstream:rstrip=2 refs/remotes
 test_atom head upstream:rstrip=-2 refs/remotes
+test_atom head upstream:strip=2 origin/master
+test_atom head upstream:strip=-2 origin/master
 test_atom head push refs/remotes/myfork/master
 test_atom head push:short myfork/master
 test_atom head push:lstrip=1 remotes/myfork/master
 test_atom head push:lstrip=-1 master
 test_atom head push:rstrip=1 refs/remotes/myfork
 test_atom head push:rstrip=-1 refs
+test_atom head push:strip=1 remotes/myfork/master
+test_atom head push:strip=-1 master
 test_atom head objecttype commit
 test_atom head objectsize 171
 test_atom head objectname $(git rev-parse refs/heads/master)
@@ -636,6 +644,10 @@ EOF
 test_expect_success 'Verify usage of %(symref:lstrip) atom' '
 	git for-each-ref --format="%(symref:lstrip=2)" refs/heads/sym > actual &&
 	git for-each-ref --format="%(symref:lstrip=-2)" refs/heads/sym >> actual &&
+	test_cmp expected actual &&
+
+	git for-each-ref --format="%(symref:strip=2)" refs/heads/sym > actual &&
+	git for-each-ref --format="%(symref:strip=-2)" refs/heads/sym >> actual &&
 	test_cmp expected actual
 '