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From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: git@vger.kernel.org
Cc: "Wink Saville" <wink@saville.com>,
	"Jacob Keller" <jacob.keller@gmail.com>,
	"Bryan Turner" <bturner@atlassian.com>,
	"Junio C Hamano" <gitster@pobox.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Jeff King" <peff@peff.net>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: [PATCH 8/8] fetch: stop clobbering existing tags without --force
Date: Sun, 29 Apr 2018 20:21:00 +0000	[thread overview]
Message-ID: <20180429202100.32353-9-avarab@gmail.com> (raw)
In-Reply-To: <20180429202100.32353-1-avarab@gmail.com>
In-Reply-To: <CACBZZX7HFnEMD8PKWj0c7VWqv=yeYCXYJjy-5YPZnF_pJAy0jw@mail.gmail.com>

Change "fetch" to treat "+" in refspecs (aka --force) to mean we
should clobber a local tag of the same name.

This changes the long-standing behavior of "fetch" added in
853a3697dc ("[PATCH] Multi-head fetch.", 2005-08-20), before this
change all tag fetches effectively had --force enabled. The original
rationale in that change was:

    > Tags need not be pointing at commits so there is no way to
    > guarantee "fast-forward" anyway.

That comment and the rest of the history of "fetch" shows that the
"+" (--force) part of refpecs was only conceived for branch updates,
while tags have accepted any changes from upstream unconditionally and
clobbered the local tag object. Changing this behavior has been
discussed as early as 2011[1].

I the current behavior doesn't make sense, it easily results in local
tags accidentally being clobbered. Ideally we'd namespace our tags
per-remote, but as with my 97716d217c ("fetch: add a --prune-tags
option and fetch.pruneTags config", 2018-02-09) it's easier to work
around the current implementation than to fix the root cause, so this
implements suggestion #1 from [1], "fetch" now only clobbers the tag
if either "+" is provided as part of the refspec, or if "--force" is
provided on the command-line.

This also makes it nicely symmetrical with how "tag" itself
works. We'll now refuse to clobber any existing tags unless "--force"
is supplied, whether that clobbering would happen by clobbering a
local tag with "tag", or by fetching it from the remote with "fetch".

It's still not at all nicely symmetrical with how "git push" works, as
discussed in the updated pull-fetch-param.txt documentation, but this
change brings them more into line with one another. I don't think
there's any reason "fetch" couldn't fully converge with the behavior
used by "push", but that's a topic for another change.

One of the tests added in 31b808a032 ("clone --single: limit the fetch
refspec to fetched branch", 2012-09-20) is being changed to use
--force where a clone would clobber a tag. This changes nothing about
the existing behavior of the test.

1. https://public-inbox.org/git/20111123221658.GA22313@sigill.intra.peff.net/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 Documentation/fetch-options.txt    | 15 ++++++++++-----
 Documentation/pull-fetch-param.txt | 22 ++++++++++++++++------
 builtin/fetch.c                    | 20 +++++++++++++-------
 t/t5516-fetch-push.sh              |  5 +++--
 t/t5612-clone-refspec.sh           |  4 ++--
 5 files changed, 44 insertions(+), 22 deletions(-)

diff --git a/Documentation/fetch-options.txt b/Documentation/fetch-options.txt
index 8631e365f4..5b4fc36866 100644
--- a/Documentation/fetch-options.txt
+++ b/Documentation/fetch-options.txt
@@ -49,11 +49,16 @@ endif::git-pull[]
 
 -f::
 --force::
-	When 'git fetch' is used with `<rbranch>:<lbranch>`
-	refspec, it refuses to update the local branch
-	`<lbranch>` unless the remote branch `<rbranch>` it
-	fetches is a descendant of `<lbranch>`.  This option
-	overrides that check.
+	When 'git fetch' is used with `<src>:<dst>` refspec it might
+	refuse to update the local branch as discussed
+ifdef::git-pull[]
+	in the `<refspec>` part of the linkgit:git-fetch[1]
+	documentation.
+endif::git-pull[]
+ifndef::git-pull[]
+	in the `<refspec>` part below.
+endif::git-pull[]
+	This option overrides that check.
 
 -k::
 --keep::
diff --git a/Documentation/pull-fetch-param.txt b/Documentation/pull-fetch-param.txt
index c579793af5..672e8bc1c0 100644
--- a/Documentation/pull-fetch-param.txt
+++ b/Documentation/pull-fetch-param.txt
@@ -32,12 +32,22 @@ name.
 `tag <tag>` means the same as `refs/tags/<tag>:refs/tags/<tag>`;
 it requests fetching everything up to the given tag.
 +
-The remote ref that matches <src>
-is fetched, and if <dst> is not empty string, the local
-ref that matches it is fast-forwarded using <src>.
-If the optional plus `+` is used, the local ref
-is updated even if it does not result in a fast-forward
-update.
+The remote ref that matches <src> is fetched, and if <dst> is not
+empty string, an attempt is made to update the local ref that matches
+it.
++
+Whether that update is allowed is confusingly not the inverse of
+whether a server will accept a push as described in the `<refspec>...`
+section of linkgit:git-push[1]. If it's a commit under `refs/heads/*`
+only fast-forwards are allowed, but unlike what linkgit:git-push[1]
+will accept clobbering any ref pointing to blobs, trees etc. in any
+other namespace will be accepted, but commits in any ref
+namespace. Those apply the same fast-forward rule. An exception to
+this is that as of Git version 2.18 any object under `refs/tags/*` is
+protected from updates.
++
+If the optional plus `+` is used, the local ref is updated if the
+update would have otherwise been rejected.
 +
 [NOTE]
 When the remote branch you want to fetch is known to
diff --git a/builtin/fetch.c b/builtin/fetch.c
index dcdfc66f09..e3a44b582a 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -126,7 +126,7 @@ static struct option builtin_fetch_options[] = {
 		 N_("append to .git/FETCH_HEAD instead of overwriting")),
 	OPT_STRING(0, "upload-pack", &upload_pack, N_("path"),
 		   N_("path to upload pack on remote end")),
-	OPT__FORCE(&force, N_("force overwrite of local branch"), 0),
+	OPT__FORCE(&force, N_("force overwrite of local reference"), 0),
 	OPT_BOOL('m', "multiple", &multiple,
 		 N_("fetch from multiple remotes")),
 	OPT_SET_INT('t', "tags", &tags,
@@ -664,12 +664,18 @@ static int update_local_ref(struct ref *ref,
 
 	if (!is_null_oid(&ref->old_oid) &&
 	    starts_with(ref->name, "refs/tags/")) {
-		int r;
-		r = s_update_ref("updating tag", ref, 0);
-		format_display(display, r ? '!' : 't', _("[tag update]"),
-			       r ? _("unable to update local ref") : NULL,
-			       remote, pretty_ref, summary_width);
-		return r;
+		if (force || ref->force) {
+			int r;
+			r = s_update_ref("updating tag", ref, 0);
+			format_display(display, r ? '!' : 't', _("[tag update]"),
+				       r ? _("unable to update local ref") : NULL,
+				       remote, pretty_ref, summary_width);
+			return r;
+		} else {
+			format_display(display, '!', _("[rejected]"), _("would clobber existing tag"),
+				       remote, pretty_ref, summary_width);
+			return 1;
+		}
 	}
 
 	current = lookup_commit_reference_gently(&ref->old_oid, 1);
diff --git a/t/t5516-fetch-push.sh b/t/t5516-fetch-push.sh
index 9cf14c5cc1..327737ecaf 100755
--- a/t/t5516-fetch-push.sh
+++ b/t/t5516-fetch-push.sh
@@ -1007,7 +1007,7 @@ test_force_fetch_tag () {
 	tag_type_description=$1
 	tag_args=$2
 
-	test_expect_success "fetch will clobber an existing $tag_type_description" "
+	test_expect_success "fetch will not clobber an existing $tag_type_description without --force" "
 		mk_test testrepo heads/master &&
 		mk_child testrepo child1 &&
 		mk_child testrepo child2 &&
@@ -1019,7 +1019,8 @@ test_force_fetch_tag () {
 			git add file1 &&
 			git commit -m 'file1' &&
 			git tag $tag_args Tag &&
-			git -C ../child1 fetch origin tag Tag
+			test_must_fail git -C ../child1 fetch origin tag Tag &&
+			git -C ../child1 fetch origin '+refs/tags/*:refs/tags/*'
 		)
 	"
 }
diff --git a/t/t5612-clone-refspec.sh b/t/t5612-clone-refspec.sh
index fac5a73851..6ea8f50dae 100755
--- a/t/t5612-clone-refspec.sh
+++ b/t/t5612-clone-refspec.sh
@@ -104,7 +104,7 @@ test_expect_success 'clone with --no-tags' '
 test_expect_success '--single-branch while HEAD pointing at master' '
 	(
 		cd dir_master &&
-		git fetch &&
+		git fetch --force &&
 		git for-each-ref refs/remotes/origin |
 		sed -e "/HEAD$/d" \
 		    -e "s|/remotes/origin/|/heads/|" >../actual
@@ -115,7 +115,7 @@ test_expect_success '--single-branch while HEAD pointing at master' '
 	test_cmp expect actual &&
 	(
 		cd dir_master &&
-		git fetch --tags &&
+		git fetch --tags --force &&
 		git for-each-ref refs/tags >../actual
 	) &&
 	git for-each-ref refs/tags >expect &&
-- 
2.17.0.290.gded63e768a


  parent reply	other threads:[~2018-04-29 20:21 UTC|newest]

Thread overview: 101+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-24 19:57 Fetching tags overwrites existing tags Wink Saville
2018-04-24 23:48 ` Jacob Keller
2018-04-25  0:52 ` Junio C Hamano
2018-04-25  1:29   ` Jacob Keller
2018-04-25  1:31   ` Wink Saville
2018-04-26 19:39     ` Wink Saville
2018-04-26 22:50       ` Junio C Hamano
2018-04-26 23:24         ` Junio C Hamano
2018-04-27 18:50           ` [RFC PATCH v2] Teach remote add the --prefix-tags option Wink Saville
2018-04-27 19:08           ` Fetching tags overwrites existing tags Wink Saville
2018-04-27 19:13             ` Bryan Turner
2018-05-04 15:56               ` Jacob Keller
2018-04-28  7:26             ` Jacob Keller
2018-04-28 18:27           ` [RFC PATCH v3] Teach remote add the --remote-tags option Wink Saville
2018-04-28 19:00             ` Wink Saville
2018-04-28 21:27               ` Wink Saville
2018-05-01 16:59           ` [RFC PATCH v4 0/3] Optional sub hierarchy for remote tags Wink Saville
2018-05-01 19:24             ` Ævar Arnfjörð Bjarmason
2018-05-01 19:45               ` Jacob Keller
2018-05-01 20:34                 ` Wink Saville
2018-05-01 23:24                 ` Junio C Hamano
2018-05-02  0:08                   ` Jacob Keller
2018-05-01 23:28               ` Junio C Hamano
2018-05-01 16:59           ` [RFC PATCH v4 1/3] Teach remote add the --remote-tags option Wink Saville
2018-05-01 18:50             ` Ævar Arnfjörð Bjarmason
2018-05-08 10:26             ` Kaartic Sivaraam
2018-05-01 16:59           ` [RFC PATCH v4 2/3] Teach tag to list remote-tags Wink Saville
2018-05-01 16:59           ` [RFC PATCH v4 3/3] Test git remote add -f --remote-tags Wink Saville
2018-04-27 19:46 ` Fetching tags overwrites existing tags Ævar Arnfjörð Bjarmason
2018-04-29 20:20   ` [PATCH 0/8] "git fetch" should not clobber existing tags without --force Ævar Arnfjörð Bjarmason
2018-07-31 13:07     ` [PATCH v2 00/10] " Ævar Arnfjörð Bjarmason
2018-08-13 19:22       ` [PATCH v3 0/7] Prep for " Ævar Arnfjörð Bjarmason
2018-08-13 20:29         ` Junio C Hamano
2018-08-13 20:37           ` Ævar Arnfjörð Bjarmason
2018-08-30 20:12         ` [PATCH v4 0/6] " Ævar Arnfjörð Bjarmason
2018-08-31 20:09           ` [PATCH v5 0/9] git " Ævar Arnfjörð Bjarmason
2018-08-31 20:09           ` [PATCH v5 1/9] fetch: change "branch" to "reference" in --force -h output Ævar Arnfjörð Bjarmason
2018-08-31 20:09           ` [PATCH v5 2/9] push tests: make use of unused $1 in test description Ævar Arnfjörð Bjarmason
2018-08-31 21:07             ` Junio C Hamano
2018-08-31 22:02               ` Ævar Arnfjörð Bjarmason
2018-08-31 20:09           ` [PATCH v5 3/9] push tests: use spaces in interpolated string Ævar Arnfjörð Bjarmason
2018-08-31 20:09           ` [PATCH v5 4/9] fetch tests: add a test for clobbering tag behavior Ævar Arnfjörð Bjarmason
2018-08-31 20:10           ` [PATCH v5 5/9] push doc: remove confusing mention of remote merger Ævar Arnfjörð Bjarmason
2018-08-31 20:10           ` [PATCH v5 6/9] push doc: move mention of "tag <tag>" later in the prose Ævar Arnfjörð Bjarmason
2018-08-31 20:10           ` [PATCH v5 7/9] push doc: correct lies about how push refspecs work Ævar Arnfjörð Bjarmason
2018-08-31 20:10           ` [PATCH v5 8/9] fetch: document local ref updates with/without --force Ævar Arnfjörð Bjarmason
2018-08-31 20:10           ` [PATCH v5 9/9] fetch: stop clobbering existing tags without --force Ævar Arnfjörð Bjarmason
2018-08-30 20:12         ` [PATCH v4 1/6] fetch: change "branch" to "reference" in --force -h output Ævar Arnfjörð Bjarmason
2018-08-30 20:12         ` [PATCH v4 2/6] push tests: correct quoting in interpolated string Ævar Arnfjörð Bjarmason
2018-08-30 21:20           ` Junio C Hamano
2018-08-30 20:12         ` [PATCH v4 3/6] fetch tests: add a test for clobbering tag behavior Ævar Arnfjörð Bjarmason
2018-08-30 21:22           ` Junio C Hamano
2018-08-30 20:12         ` [PATCH v4 4/6] push doc: correct lies about how push refspecs work Ævar Arnfjörð Bjarmason
2018-08-30 21:31           ` Junio C Hamano
2018-08-30 22:34           ` Ævar Arnfjörð Bjarmason
2018-08-31 16:24             ` Junio C Hamano
2018-08-31 16:35               ` Ævar Arnfjörð Bjarmason
2018-08-30 20:12         ` [PATCH v4 5/6] fetch: document local ref updates with/without --force Ævar Arnfjörð Bjarmason
2018-08-30 20:12         ` [PATCH v4 6/6] fetch: stop clobbering existing tags without --force Ævar Arnfjörð Bjarmason
2018-08-30 21:43           ` Junio C Hamano
2018-08-13 19:22       ` [PATCH v3 1/7] fetch tests: change "Tag" test tag to "testTag" Ævar Arnfjörð Bjarmason
2018-08-13 19:22       ` [PATCH v3 2/7] push tests: remove redundant 'git push' invocation Ævar Arnfjörð Bjarmason
2018-08-13 19:22       ` [PATCH v3 3/7] push tests: fix logic error in "push" test assertion Ævar Arnfjörð Bjarmason
2018-08-13 19:22       ` [PATCH v3 4/7] push tests: add more testing for forced tag pushing Ævar Arnfjörð Bjarmason
2018-08-13 19:22       ` [PATCH v3 5/7] push tests: assert re-pushing annotated tags Ævar Arnfjörð Bjarmason
2018-08-13 19:22       ` [PATCH v3 6/7] fetch tests: correct a comment "remove it" -> "remove them" Ævar Arnfjörð Bjarmason
2018-08-13 19:22       ` [PATCH v3 7/7] pull doc: fix a long-standing grammar error Ævar Arnfjörð Bjarmason
2018-07-31 13:07     ` [PATCH v2 01/10] fetch tests: change "Tag" test tag to "testTag" Ævar Arnfjörð Bjarmason
2018-07-31 13:07     ` [PATCH v2 02/10] push tests: remove redundant 'git push' invocation Ævar Arnfjörð Bjarmason
2018-07-31 13:07     ` [PATCH v2 03/10] push tests: fix logic error in "push" test assertion Ævar Arnfjörð Bjarmason
2018-07-31 13:07     ` [PATCH v2 04/10] push tests: add more testing for forced tag pushing Ævar Arnfjörð Bjarmason
2018-07-31 13:07     ` [PATCH v2 05/10] push tests: assert re-pushing annotated tags Ævar Arnfjörð Bjarmason
2018-07-31 13:07     ` [PATCH v2 06/10] push doc: correct lies about how push refspecs work Ævar Arnfjörð Bjarmason
2018-07-31 17:40       ` Junio C Hamano
2018-08-30 14:52         ` Ævar Arnfjörð Bjarmason
2018-08-30 15:23           ` Junio C Hamano
2018-08-30 16:59             ` Ævar Arnfjörð Bjarmason
2018-07-31 13:07     ` [PATCH v2 07/10] fetch tests: correct a comment "remove it" -> "remove them" Ævar Arnfjörð Bjarmason
2018-07-31 13:07     ` [PATCH v2 08/10] fetch tests: add a test clobbering tag behavior Ævar Arnfjörð Bjarmason
2018-07-31 17:48       ` Junio C Hamano
2018-07-31 13:07     ` [PATCH v2 09/10] pull doc: fix a long-standing grammar error Ævar Arnfjörð Bjarmason
2018-07-31 13:07     ` [PATCH v2 10/10] fetch: stop clobbering existing tags without --force Ævar Arnfjörð Bjarmason
2018-07-31 18:03       ` Junio C Hamano
2018-04-29 20:20   ` [PATCH 1/8] push tests: remove redundant 'git push' invocation Ævar Arnfjörð Bjarmason
2018-04-29 20:20   ` [PATCH 2/8] push tests: fix logic error in "push" test assertion Ævar Arnfjörð Bjarmason
2018-04-29 20:20   ` [PATCH 3/8] push tests: add more testing for forced tag pushing Ævar Arnfjörð Bjarmason
2018-05-07 10:09     ` Kaartic Sivaraam
2018-05-08  2:35     ` Junio C Hamano
2018-05-08  3:19       ` Junio C Hamano
2018-05-08  9:52         ` Kaartic Sivaraam
2018-05-08 10:19     ` Kaartic Sivaraam
2018-04-29 20:20   ` [PATCH 4/8] push tests: assert re-pushing annotated tags Ævar Arnfjörð Bjarmason
2018-05-08  4:30     ` Junio C Hamano
2018-05-08 14:05     ` SZEDER Gábor
2018-04-29 20:20   ` [PATCH 5/8] push doc: correct lies about how push refspecs work Ævar Arnfjörð Bjarmason
2018-05-08  5:14     ` Junio C Hamano
2018-04-29 20:20   ` [PATCH 6/8] fetch tests: correct a comment "remove it" -> "remove them" Ævar Arnfjörð Bjarmason
2018-04-29 20:20   ` [PATCH 7/8] fetch tests: add a test clobbering tag behavior Ævar Arnfjörð Bjarmason
2018-04-29 20:21   ` Ævar Arnfjörð Bjarmason [this message]
2018-05-08  5:37     ` [PATCH 8/8] fetch: stop clobbering existing tags without --force Junio C Hamano
2018-05-01 17:11 ` Fetching tags overwrites existing tags Wink Saville

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