[PATCH 1/3] tag: prevent recursive tags

From: Denton Liu <liu.denton@gmail.com>
To: Git Mailing List <git@vger.kernel.org>
Cc: "Jeff King" <peff@peff.net>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Robert Dailey" <rcdailey.lists@gmail.com>
Subject: [PATCH 1/3] tag: prevent recursive tags
Date: Tue, 26 Mar 2019 00:53:18 -0700	[thread overview]
Message-ID: <c371a653b4049256f3427e467b144385ee47ef43.1553586707.git.liu.denton@gmail.com> (raw)
In-Reply-To: <cover.1553586707.git.liu.denton@gmail.com>

Robert Dailey reported confusion on the mailing list about a recursive
tag which was most likely created by mistake. Jeff King noted that this
isn't a very common case so, most likely, creating a tag-to-a-tag is a
user-error.

Prevent mistakes by erroring and providing advice on recursive tags,
unless "--allow-recursive-tag" is specified. Fix tests that fail as a
result of this change.

Reported-by: Robert Dailey <rcdailey.lists@gmail.com>
Helped-by: Jeff King <peff@peff.net>
Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Denton Liu <liu.denton@gmail.com>
---
 advice.c                       |  2 ++
 advice.h                       |  1 +
 builtin/tag.c                  | 30 ++++++++++++++++++++++++++----
 t/annotate-tests.sh            |  2 +-
 t/t0410-partial-clone.sh       |  2 +-
 t/t4205-log-pretty-formats.sh  |  2 +-
 t/t5305-include-tag.sh         |  2 +-
 t/t5500-fetch-pack.sh          |  2 +-
 t/t6302-for-each-ref-filter.sh |  4 ++--
 t/t7004-tag.sh                 |  4 ++--
 t/t9350-fast-export.sh         |  4 ++--
 11 files changed, 40 insertions(+), 15 deletions(-)

diff --git a/advice.c b/advice.c
index 567209aa79..f31889e6de 100644
--- a/advice.c
+++ b/advice.c
@@ -26,6 +26,7 @@ int advice_ignored_hook = 1;
 int advice_waiting_for_editor = 1;
 int advice_graft_file_deprecated = 1;
 int advice_checkout_ambiguous_remote_branch_name = 1;
+int advice_recursive_tag = 1;
 
 static int advice_use_color = -1;
 static char advice_colors[][COLOR_MAXLEN] = {
@@ -81,6 +82,7 @@ static struct {
 	{ "waitingForEditor", &advice_waiting_for_editor },
 	{ "graftFileDeprecated", &advice_graft_file_deprecated },
 	{ "checkoutAmbiguousRemoteBranchName", &advice_checkout_ambiguous_remote_branch_name },
+	{ "recursiveTag", &advice_recursive_tag },
 
 	/* make this an alias for backward compatibility */
 	{ "pushNonFastForward", &advice_push_update_rejected }
diff --git a/advice.h b/advice.h
index f875f8cd8d..66aa39757c 100644
--- a/advice.h
+++ b/advice.h
@@ -26,6 +26,7 @@ extern int advice_ignored_hook;
 extern int advice_waiting_for_editor;
 extern int advice_graft_file_deprecated;
 extern int advice_checkout_ambiguous_remote_branch_name;
+extern int advice_recursive_tag;
 
 int git_default_advice_config(const char *var, const char *value);
 __attribute__((format (printf, 1, 2)))
diff --git a/builtin/tag.c b/builtin/tag.c
index 02f6bd1279..0b44a3cbc1 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -22,10 +22,11 @@
 #include "ref-filter.h"
 
 static const char * const git_tag_usage[] = {
-	N_("git tag [-a | -s | -u <key-id>] [-f] [-m <msg> | -F <file>] <tagname> [<head>]"),
+	N_("git tag [-a | -s | -u <key-id>] [-f] [-m <msg> | -F <file>] [--allow-recursive-tag]\n"
+		"\t\t<tagname> [<head>]"),
 	N_("git tag -d <tagname>..."),
-	N_("git tag -l [-n[<num>]] [--contains <commit>] [--no-contains <commit>] [--points-at <object>]"
-		"\n\t\t[--format=<format>] [--[no-]merged [<commit>]] [<pattern>...]"),
+	N_("git tag -l [-n[<num>]] [--contains <commit>] [--no-contains <commit>] [--points-at <object>]\n"
+		"\t\t[--format=<format>] [--[no-]merged [<commit>]] [<pattern>...]"),
 	N_("git tag -v [--format=<format>] <tagname>..."),
 	NULL
 };
@@ -197,6 +198,7 @@ static int build_tag_object(struct strbuf *buf, int sign, struct object_id *resu
 struct create_tag_options {
 	unsigned int message_given:1;
 	unsigned int use_editor:1;
+	unsigned int allow_recursive_tag;
 	unsigned int sign;
 	enum {
 		CLEANUP_NONE,
@@ -205,6 +207,17 @@ struct create_tag_options {
 	} cleanup_mode;
 };
 
+static const char message_advice_recursive_tag[] =
+	N_("The object '%s' referred to by your new tag is already a tag.\n"
+	   "\n"
+	   "If you meant to create a tag of a tag, use:\n"
+	   "\n"
+	    "\tgit tag --allow-recursive-tag %s\n"
+	   "\n"
+	   "If you meant to tag the object that it points to, use:\n"
+	   "\n"
+	   "\tgit tag %s^{}");
+
 static void create_tag(const struct object_id *object, const char *tag,
 		       struct strbuf *buf, struct create_tag_options *opt,
 		       struct object_id *prev, struct object_id *result)
@@ -215,7 +228,14 @@ static void create_tag(const struct object_id *object, const char *tag,
 
 	type = oid_object_info(the_repository, object, NULL);
 	if (type <= OBJ_NONE)
-	    die(_("bad object type."));
+		die(_("bad object type."));
+
+	if (type == OBJ_TAG && !opt->allow_recursive_tag) {
+		error(_("refusing to make a recursive tag"));
+		if (advice_recursive_tag)
+			advise(_(message_advice_recursive_tag), tag, tag, tag);
+		exit(1);
+	}
 
 	strbuf_addf(&header,
 		    "object %s\n"
@@ -403,6 +423,8 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 					N_("use another key to sign the tag")),
 		OPT__FORCE(&force, N_("replace the tag if exists"), 0),
 		OPT_BOOL(0, "create-reflog", &create_reflog, N_("create a reflog")),
+		OPT_BOOL(0, "allow-recursive-tag", &opt.allow_recursive_tag,
+					N_("allow recursive tags to be made")),
 
 		OPT_GROUP(N_("Tag listing options")),
 		OPT_COLUMN(0, "column", &colopts, N_("show tag list in columns")),
diff --git a/t/annotate-tests.sh b/t/annotate-tests.sh
index 6da48a2e0a..841f922e07 100644
--- a/t/annotate-tests.sh
+++ b/t/annotate-tests.sh
@@ -70,7 +70,7 @@ test_expect_success 'blame 1 author' '
 
 test_expect_success 'blame by tag objects' '
 	git tag -m "test tag" testTag &&
-	git tag -m "test tag #2" testTag2 testTag &&
+	git tag -m "test tag #2" --allow-recursive-tag testTag2 testTag &&
 	check_count -h testTag A 2 &&
 	check_count -h testTag2 A 2
 '
diff --git a/t/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
index bce02788e6..5f06c2d76f 100755
--- a/t/t0410-partial-clone.sh
+++ b/t/t0410-partial-clone.sh
@@ -16,7 +16,7 @@ pack_as_from_promisor () {
 
 promise_and_delete () {
 	HASH=$(git -C repo rev-parse "$1") &&
-	git -C repo tag -a -m message my_annotated_tag "$HASH" &&
+	git -C repo tag -a -m message my_annotated_tag --allow-recursive-tag "$HASH" &&
 	git -C repo rev-parse my_annotated_tag | pack_as_from_promisor &&
 	# tag -d prints a message to stdout, so redirect it
 	git -C repo tag -d my_annotated_tag >/dev/null &&
diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index f42a69faa2..018550f3b2 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -511,7 +511,7 @@ test_expect_success 'set up log decoration tests' '
 
 test_expect_success 'log decoration properly follows tag chain' '
 	git tag -a tag1 -m tag1 &&
-	git tag -a tag2 -m tag2 tag1 &&
+	git tag -a tag2 -m tag2 --allow-recursive-tag tag1 &&
 	git tag -d tag1 &&
 	git commit --amend -m shorter &&
 	git log --no-walk --tags --pretty="%H %d" --decorate=full >actual &&
diff --git a/t/t5305-include-tag.sh b/t/t5305-include-tag.sh
index a5eca210b8..c99850c1c0 100755
--- a/t/t5305-include-tag.sh
+++ b/t/t5305-include-tag.sh
@@ -68,7 +68,7 @@ test_expect_success 'check unpacked result (have commit, have tag)' '
 test_expect_success 'create hidden inner tag' '
 	test_commit commit &&
 	git tag -m inner inner HEAD &&
-	git tag -m outer outer inner &&
+	git tag -m outer --allow-recursive-tag outer inner &&
 	git tag -d inner
 '
 
diff --git a/t/t5500-fetch-pack.sh b/t/t5500-fetch-pack.sh
index 49c540b1e1..c549b37aec 100755
--- a/t/t5500-fetch-pack.sh
+++ b/t/t5500-fetch-pack.sh
@@ -562,7 +562,7 @@ test_expect_success 'test --all wrt tag to non-commits' '
 		hello tag
 	EOF
 	) &&
-	git tag -a -m "tag -> tag" tag-to-tag $tag &&
+	git tag -a -m "tag -> tag" --allow-recursive-tag tag-to-tag $tag &&
 
 	# `fetch-pack --all` should succeed fetching all those objects.
 	mkdir fetchall &&
diff --git a/t/t6302-for-each-ref-filter.sh b/t/t6302-for-each-ref-filter.sh
index fc067ed672..f7b56ae195 100755
--- a/t/t6302-for-each-ref-filter.sh
+++ b/t/t6302-for-each-ref-filter.sh
@@ -12,7 +12,7 @@ test_expect_success 'setup some history and refs' '
 	git checkout -b side &&
 	test_commit four &&
 	git tag -m "An annotated tag" annotated-tag &&
-	git tag -m "Annonated doubly" doubly-annotated-tag annotated-tag &&
+	git tag -m "Annonated doubly" --allow-recursive-tag doubly-annotated-tag annotated-tag &&
 
 	# Note that these "signed" tags might not actually be signed.
 	# Tests which care about the distinction should be marked
@@ -24,7 +24,7 @@ test_expect_success 'setup some history and refs' '
 		sign=
 	fi &&
 	git tag $sign -m "A signed tag" signed-tag &&
-	git tag $sign -m "Signed doubly" doubly-signed-tag signed-tag &&
+	git tag $sign -m "Signed doubly" --allow-recursive-tag doubly-signed-tag signed-tag &&
 
 	git checkout master &&
 	git update-ref refs/odd/spot master
diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
index 0b01862c23..7a7c0ccee9 100755
--- a/t/t7004-tag.sh
+++ b/t/t7004-tag.sh
@@ -1265,7 +1265,7 @@ echo "A message for another tag" >>expect
 echo '-----BEGIN PGP SIGNATURE-----' >>expect
 test_expect_success GPG \
 	'creating a signed tag pointing to another tag should succeed' '
-	git tag -s -m "A message for another tag" tag-signed-tag signed-tag &&
+	git tag -s -m "A message for another tag" --allow-recursive-tag tag-signed-tag signed-tag &&
 	get_tag_msg tag-signed-tag >actual &&
 	test_cmp expect actual
 '
@@ -1690,7 +1690,7 @@ test_expect_success '--points-at finds annotated tags of commits' '
 '
 
 test_expect_success '--points-at finds annotated tags of tags' '
-	git tag -m "describing the v4.0 tag object" \
+	git tag -m "describing the v4.0 tag object" --allow-recursive-tag \
 		annotated-again-v4.0 annotated-v4.0 &&
 	cat >expect <<-\EOF &&
 	annotated-again-v4.0
diff --git a/t/t9350-fast-export.sh b/t/t9350-fast-export.sh
index 5690fe2810..b5ed7e119a 100755
--- a/t/t9350-fast-export.sh
+++ b/t/t9350-fast-export.sh
@@ -441,8 +441,8 @@ test_expect_success 'set-up a few more tags for tag export tests' '
 	HEAD_TREE=$(git show -s --pretty=raw HEAD | grep tree | sed "s/tree //") &&
 	git tag    tree_tag        -m "tagging a tree" $HEAD_TREE &&
 	git tag -a tree_tag-obj    -m "tagging a tree" $HEAD_TREE &&
-	git tag    tag-obj_tag     -m "tagging a tag" tree_tag-obj &&
-	git tag -a tag-obj_tag-obj -m "tagging a tag" tree_tag-obj
+	git tag    tag-obj_tag     -m "tagging a tag" --allow-recursive-tag tree_tag-obj &&
+	git tag -a tag-obj_tag-obj -m "tagging a tag" --allow-recursive-tag tree_tag-obj
 '
 
 test_expect_success 'tree_tag'        '
-- 
2.21.0.512.g57bf1b23e1

