clone: add a --no-tags option to clone without tags

Add a --no-tags option to clone without fetching any tags.

Without this change there's no easy way to clone a repository without
also fetching its tags.

When supplying --single-branch the primary remote branch will be
cloned, but in addition tags will be followed & retrieved. Now
--no-tags can be added --single-branch to clone a repository without
tags, and which only tracks a single upstream branch.

This option works without --single-branch as well, and will do a
normal clone but not fetch any tags.

Many git commands pay some fixed overhead as a function of the number
of references. E.g. creating ~40k tags in linux.git will cause a
command like `git log -1 >/dev/null` to run in over a second instead
of in a matter of milliseconds, in addition numerous other things will
slow down, e.g. "git log <TAB>" with the bash completion will slowly
show ~40k references instead of 1.

The user might want to avoid all of that overhead to simply use a
repository like that to browse the "master" branch, or something like
a CI tool might want to keep that one branch up-to-date without caring
about any other references.

Without this change the only way of accomplishing this was either by
manually tweaking the config in a fresh repository:

    git init git &&
    cat >git/.git/config <<EOF &&
    [remote "origin"]
        url = git@github.com:git/git.git
        tagOpt = --no-tags
        fetch = +refs/heads/master:refs/remotes/origin/master
    [branch "master"]
        remote = origin
        merge = refs/heads/master
    EOF
    cd git &&
    git pull

Which requires hardcoding the "master" name, which may not be the main
--single-branch would have retrieved, or alternatively by setting
tagOpt=--no-tags right after cloning & deleting any existing tags:

    git clone --single-branch git@github.com:git/git.git &&
    cd git &&
    git config remote.origin.tagOpt --no-tags &&
    git tag -l | xargs git tag -d

Which of course was also subtly buggy if --branch was pointed at a
tag, leaving the user in a detached head:

    git clone --single-branch --branch v2.12.0 git@github.com:git/git.git &&
    cd git &&
    git config remote.origin.tagOpt --no-tags &&
    git tag -l | xargs git tag -d

Now all this complexity becomes the much simpler:

    git clone --single-branch --no-tags git@github.com:git/git.git

Or in the case of cloning a single tag "branch":

    git clone --single-branch --branch v2.12.0 --no-tags git@github.com:git/git.git

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 74 insertions, 2 deletions

diff --git a/t/t5612-clone-refspec.sh b/t/t5612-clone-refspec.sh
index 97c847fab6..fac5a73851 100755
--- a/t/t5612-clone-refspec.sh
+++ b/t/t5612-clone-refspec.sh
@@ -17,13 +17,20 @@ test_expect_success 'setup' '
 	echo four >file &&
 	git commit -a -m four &&
 	git checkout master &&
+	git tag five &&
 
 	# default clone
 	git clone . dir_all &&
 
+	# default clone --no-tags
+	git clone --no-tags . dir_all_no_tags &&
+
 	# default --single that follows HEAD=master
 	git clone --single-branch . dir_master &&
 
+	# default --single that follows HEAD=master with no tags
+	git clone --single-branch --no-tags . dir_master_no_tags &&
+
 	# default --single that follows HEAD=side
 	git checkout side &&
 	git clone --single-branch . dir_side &&
@@ -45,6 +52,9 @@ test_expect_success 'setup' '
 	# explicit --single with tag
 	git clone --single-branch --branch two . dir_tag &&
 
+	# explicit --single with tag and --no-tags
+	git clone --single-branch --no-tags --branch two . dir_tag_no_tags &&
+
 	# advance both "master" and "side" branches
 	git checkout side &&
 	echo five >file &&
@@ -77,7 +87,18 @@ test_expect_success 'by default no tags will be kept updated' '
 		git for-each-ref refs/tags >../actual
 	) &&
 	git for-each-ref refs/tags >expect &&
-	test_must_fail test_cmp expect actual
+	test_must_fail test_cmp expect actual &&
+	test_line_count = 2 actual
+'
+
+test_expect_success 'clone with --no-tags' '
+	(
+		cd dir_all_no_tags &&
+		git fetch &&
+		git for-each-ref refs/tags >../actual
+	) &&
+	>expect &&
+	test_cmp expect actual
 '
 
 test_expect_success '--single-branch while HEAD pointing at master' '
@@ -90,7 +111,47 @@ test_expect_success '--single-branch while HEAD pointing at master' '
 	) &&
 	# only follow master
 	git for-each-ref refs/heads/master >expect &&
-	test_cmp expect actual
+	# get & check latest tags
+	test_cmp expect actual &&
+	(
+		cd dir_master &&
+		git fetch --tags &&
+		git for-each-ref refs/tags >../actual
+	) &&
+	git for-each-ref refs/tags >expect &&
+	test_cmp expect actual &&
+	test_line_count = 2 actual
+'
+
+test_expect_success '--single-branch while HEAD pointing at master and --no-tags' '
+	(
+		cd dir_master_no_tags &&
+		git fetch &&
+		git for-each-ref refs/remotes/origin |
+		sed -e "/HEAD$/d" \
+		    -e "s|/remotes/origin/|/heads/|" >../actual
+	) &&
+	# only follow master
+	git for-each-ref refs/heads/master >expect &&
+	test_cmp expect actual &&
+	# get tags (noop)
+	(
+		cd dir_master_no_tags &&
+		git fetch &&
+		git for-each-ref refs/tags >../actual
+	) &&
+	>expect &&
+	test_cmp expect actual &&
+	test_line_count = 0 actual &&
+	# get tags with --tags overrides tagOpt
+	(
+		cd dir_master_no_tags &&
+		git fetch --tags &&
+		git for-each-ref refs/tags >../actual
+	) &&
+	git for-each-ref refs/tags >expect &&
+	test_cmp expect actual &&
+	test_line_count = 2 actual
 '
 
 test_expect_success '--single-branch while HEAD pointing at side' '
@@ -129,6 +190,17 @@ test_expect_success '--single-branch with explicit --branch with tag fetches upd
 	test_cmp expect actual
 '
 
+test_expect_success '--single-branch with explicit --branch with tag fetches updated tag despite --no-tags' '
+	(
+		cd dir_tag_no_tags &&
+		git fetch &&
+		git for-each-ref refs/tags >../actual
+	) &&
+	git for-each-ref refs/tags/two >expect &&
+	test_cmp expect actual &&
+	test_line_count = 1 actual
+'
+
 test_expect_success '--single-branch with --mirror' '
 	(
 		cd dir_mirror &&