branch: add a --copy (-c) option to go with --move (-m)

Add the ability to --copy a branch and its reflog and configuration,
this uses the same underlying machinery as the --move (-m) option
except the reflog and configuration is copied instead of being moved.

This is useful for e.g. copying a topic branch to a new version,
e.g. work to work-2 after submitting the work topic to the list, while
preserving all the tracking info and other configuration that goes
with the branch, and unlike --move keeping the other already-submitted
branch around for reference.

Like --move, when the source branch is the currently checked out
branch the HEAD is moved to the destination branch. In the case of
--move we don't really have a choice (other than remaining on a
detached HEAD) and in order to keep the functionality consistent, we
are doing it in similar way for --copy too.

The most common usage of this feature is expected to be moving to a
new topic branch which is a copy of the current one, in that case
moving to the target branch is what the user wants, and doesn't
unexpectedly behave differently than --move would.

One outstanding caveat of this implementation is that:

    git checkout maint &&
    git checkout master &&
    git branch -c topic &&
    git checkout -

Will check out 'maint' instead of 'master'. This is because the @{-N}
feature (or its -1 shorthand "-") relies on HEAD reflogs created by
the checkout command, so in this case we'll checkout maint instead of
master, as the user might expect. What to do about that is left to a
future change.

Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Sahil Dua <sahildua2305@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 215 insertions, 0 deletions

diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 5eb752c516..5d03ad16f6 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -382,6 +382,221 @@ EOF
 	test_cmp expect actual
 '
 
+test_expect_success 'git branch -c dumps usage' '
+	test_expect_code 128 git branch -c 2>err &&
+	test_i18ngrep "branch name required" err
+'
+
+test_expect_success 'git branch --copy dumps usage' '
+	test_expect_code 128 git branch --copy 2>err &&
+	test_i18ngrep "branch name required" err
+'
+
+test_expect_success 'git branch -c d e should work' '
+	git branch -l d &&
+	git reflog exists refs/heads/d &&
+	git config branch.d.dummy Hello &&
+	git branch -c d e &&
+	git reflog exists refs/heads/d &&
+	git reflog exists refs/heads/e &&
+	echo Hello >expect &&
+	git config branch.e.dummy >actual &&
+	test_cmp expect actual &&
+	echo Hello >expect &&
+	git config branch.d.dummy >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'git branch --copy is a synonym for -c' '
+	git branch -l copy &&
+	git reflog exists refs/heads/copy &&
+	git config branch.copy.dummy Hello &&
+	git branch --copy copy copy-to &&
+	git reflog exists refs/heads/copy &&
+	git reflog exists refs/heads/copy-to &&
+	echo Hello >expect &&
+	git config branch.copy.dummy >actual &&
+	test_cmp expect actual &&
+	echo Hello >expect &&
+	git config branch.copy-to.dummy >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'git branch -c ee ef should copy and checkout branch ef' '
+	git checkout -b ee &&
+	git reflog exists refs/heads/ee &&
+	git config branch.ee.dummy Hello &&
+	git branch -c ee ef &&
+	git reflog exists refs/heads/ee &&
+	git reflog exists refs/heads/ef &&
+	test $(git config branch.ee.dummy) = Hello &&
+	test $(git config branch.ef.dummy) = Hello &&
+	test $(git rev-parse --abbrev-ref HEAD) = ef
+'
+
+test_expect_success 'git branch -c f/f g/g should work' '
+	git branch -l f/f &&
+	git reflog exists refs/heads/f/f &&
+	git config branch.f/f.dummy Hello &&
+	git branch -c f/f g/g &&
+	git reflog exists refs/heads/f/f &&
+	git reflog exists refs/heads/g/g &&
+	test $(git config branch.f/f.dummy) = Hello &&
+	test $(git config branch.g/g.dummy) = Hello
+'
+
+test_expect_success 'git branch -c m2 m2 should work' '
+	git branch -l m2 &&
+	git reflog exists refs/heads/m2 &&
+	git config branch.m2.dummy Hello &&
+	git branch -c m2 m2 &&
+	git reflog exists refs/heads/m2 &&
+	test $(git config branch.m2.dummy) = Hello
+'
+
+test_expect_success 'git branch -c zz zz/zz should fail' '
+	git branch -l zz &&
+	git reflog exists refs/heads/zz &&
+	test_must_fail git branch -c zz zz/zz
+'
+
+test_expect_success 'git branch -c b/b b should fail' '
+	git branch -l b/b &&
+	test_must_fail git branch -c b/b b
+'
+
+test_expect_success 'git branch -C o/q o/p should work when o/p exists' '
+	git branch -l o/q &&
+	git reflog exists refs/heads/o/q &&
+	git reflog exists refs/heads/o/p &&
+	git branch -C o/q o/p
+'
+
+test_expect_success 'git branch -c -f o/q o/p should work when o/p exists' '
+	git reflog exists refs/heads/o/q &&
+	git reflog exists refs/heads/o/p &&
+	git branch -c -f o/q o/p
+'
+
+test_expect_success 'git branch -c qq rr/qq should fail when r exists' '
+	git branch qq &&
+	git branch rr &&
+	test_must_fail git branch -c qq rr/qq
+'
+
+test_expect_success 'git branch -C b1 b2 should fail when b2 is checked out' '
+	git branch b1 &&
+	git checkout -b b2 &&
+	test_must_fail git branch -C b1 b2
+'
+
+test_expect_success 'git branch -C c1 c2 should succeed when c1 is checked out' '
+	git checkout -b c1 &&
+	git branch c2 &&
+	git branch -C c1 c2 &&
+	test $(git rev-parse --abbrev-ref HEAD) = c2
+'
+
+test_expect_success 'git branch -C c1 c2 should add entries to .git/logs/HEAD' '
+	msg="Branch: copied refs/heads/c1 to refs/heads/c2" &&
+	grep "$msg$" .git/logs/HEAD
+'
+
+test_expect_success 'git branch -C master should work when master is checked out' '
+	git checkout master &&
+	git branch -C master
+'
+
+test_expect_success 'git branch -C master master should work when master is checked out' '
+	git checkout master &&
+	git branch -C master master
+'
+
+test_expect_success 'git branch -C master5 master5 should work when master is checked out' '
+	git checkout master &&
+	git branch master5 &&
+	git branch -C master5 master5
+'
+
+test_expect_success 'git branch -C ab cd should overwrite existing config for cd' '
+	git branch -l cd &&
+	git reflog exists refs/heads/cd &&
+	git config branch.cd.dummy CD &&
+	git branch -l ab &&
+	git reflog exists refs/heads/ab &&
+	git config branch.ab.dummy AB &&
+	git branch -C ab cd &&
+	git reflog exists refs/heads/ab &&
+	git reflog exists refs/heads/cd &&
+	test $(git config branch.ab.dummy) = AB &&
+	test $(git config branch.cd.dummy) = AB
+'
+
+test_expect_success 'git branch -c correctly copies multiple config sections' '
+	FOO=1 &&
+	export FOO &&
+	test_when_finished "git checkout master" &&
+	git checkout -b source2 master &&
+
+	# Assert that a config file with multiple config sections has
+	# those sections preserved...
+	cat >expect <<-\EOF &&
+	branch.source2.key1=value1
+	branch.dest2.key1=value1
+	more.gar.b=age
+	branch.source2.key2=value2
+	branch.dest2.key2=value2
+	EOF
+	cat >config.branch <<\EOF &&
+;; Note the lack of -\EOF above & mixed indenting here. This is
+;; intentional, we are also testing that the formatting of copied
+;; sections is preserved.
+
+;; Comment for source2. Tabs
+[branch "source2"]
+	;; Comment for the source2 value
+	key1 = value1
+;; Comment for more.gar. Spaces
+[more "gar"]
+    ;; Comment for the more.gar value
+    b = age
+;; Comment for source2, again. Mixed tabs/spaces.
+[branch "source2"]
+    ;; Comment for the source2 value, again
+	key2 = value2
+EOF
+	cat config.branch >>.git/config &&
+	git branch -c source2 dest2 &&
+	git config -f .git/config -l | grep -F -e source2 -e dest2 -e more.gar >actual &&
+	test_cmp expect actual &&
+
+	# ...and that the comments and formatting for those sections
+	# is also preserved.
+	cat >expect <<\EOF &&
+;; Comment for source2. Tabs
+[branch "source2"]
+	;; Comment for the source2 value
+	key1 = value1
+;; Comment for more.gar. Spaces
+[branch "dest2"]
+	;; Comment for the source2 value
+	key1 = value1
+;; Comment for more.gar. Spaces
+[more "gar"]
+    ;; Comment for the more.gar value
+    b = age
+;; Comment for source2, again. Mixed tabs/spaces.
+[branch "source2"]
+    ;; Comment for the source2 value, again
+	key2 = value2
+[branch "dest2"]
+    ;; Comment for the source2 value, again
+	key2 = value2
+EOF
+	sed -n -e "/Comment for source2/,\$p" .git/config >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'deleting a symref' '
 	git branch target &&
 	git symbolic-ref refs/heads/symref refs/heads/target &&