Merge branch 'mz/pick-unborn'

Allow "git cherry-pick $commit" even when you do not have any
history behind HEAD yet.

* mz/pick-unborn:
  learn to pick/revert into unborn branch
  tests: move test_cmp_rev to test-lib-functions

10 files changed, 44 insertions, 48 deletions

diff --git a/sequencer.c b/sequencer.c
index 22604902aa..aef5e8a017 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -186,14 +186,15 @@ static int error_dirty_index(struct replay_opts *opts)
 	return -1;
 }
 
-static int fast_forward_to(const unsigned char *to, const unsigned char *from)
+static int fast_forward_to(const unsigned char *to, const unsigned char *from,
+			   int unborn)
 {
 	struct ref_lock *ref_lock;
 
 	read_cache();
 	if (checkout_fast_forward(from, to, 1))
 		exit(1); /* the callee should have complained already */
-	ref_lock = lock_any_ref_for_update("HEAD", from, 0);
+	ref_lock = lock_any_ref_for_update("HEAD", unborn ? null_sha1 : from, 0);
 	return write_ref_sha1(ref_lock, to, "cherry-pick");
 }
 
@@ -390,7 +391,7 @@ static int do_pick_commit(struct commit *commit, struct replay_opts *opts)
 	struct commit_message msg = { NULL, NULL, NULL, NULL, NULL };
 	char *defmsg = NULL;
 	struct strbuf msgbuf = STRBUF_INIT;
-	int res;
+	int res, unborn = 0;
 
 	if (opts->no_commit) {
 		/*
@@ -402,9 +403,10 @@ static int do_pick_commit(struct commit *commit, struct replay_opts *opts)
 		if (write_cache_as_tree(head, 0, NULL))
 			die (_("Your index file is unmerged."));
 	} else {
-		if (get_sha1("HEAD", head))
-			return error(_("You do not have a valid HEAD"));
-		if (index_differs_from("HEAD", 0))
+		unborn = get_sha1("HEAD", head);
+		if (unborn)
+			hashcpy(head, EMPTY_TREE_SHA1_BIN);
+		if (index_differs_from(unborn ? EMPTY_TREE_SHA1_HEX : "HEAD", 0))
 			return error_dirty_index(opts);
 	}
 	discard_cache();
@@ -435,8 +437,10 @@ static int do_pick_commit(struct commit *commit, struct replay_opts *opts)
 	else
 		parent = commit->parents->item;
 
-	if (opts->allow_ff && parent && !hashcmp(parent->object.sha1, head))
-		return fast_forward_to(commit->object.sha1, head);
+	if (opts->allow_ff &&
+	    ((parent && !hashcmp(parent->object.sha1, head)) ||
+	     (!parent && unborn)))
+	     return fast_forward_to(commit->object.sha1, head, unborn);
 
 	if (parent && parse_commit(parent) < 0)
 		/* TRANSLATORS: The first %s will be "revert" or
diff --git a/t/t1505-rev-parse-last.sh b/t/t1505-rev-parse-last.sh
index d709ecf8df..4969edb314 100755
--- a/t/t1505-rev-parse-last.sh
+++ b/t/t1505-rev-parse-last.sh
@@ -32,32 +32,24 @@ test_expect_success 'setup' '
 #
 # and 'side' should be the last branch
 
-test_rev_equivalent () {
-
-	git rev-parse "$1" > expect &&
-	git rev-parse "$2" > output &&
-	test_cmp expect output
-
-}
-
 test_expect_success '@{-1} works' '
-	test_rev_equivalent side @{-1}
+	test_cmp_rev side @{-1}
 '
 
 test_expect_success '@{-1}~2 works' '
-	test_rev_equivalent side~2 @{-1}~2
+	test_cmp_rev side~2 @{-1}~2
 '
 
 test_expect_success '@{-1}^2 works' '
-	test_rev_equivalent side^2 @{-1}^2
+	test_cmp_rev side^2 @{-1}^2
 '
 
 test_expect_success '@{-1}@{1} works' '
-	test_rev_equivalent side@{1} @{-1}@{1}
+	test_cmp_rev side@{1} @{-1}@{1}
 '
 
 test_expect_success '@{-2} works' '
-	test_rev_equivalent master @{-2}
+	test_cmp_rev master @{-2}
 '
 
 test_expect_success '@{-3} fails' '
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index 32fdc9938e..8462be1db6 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -29,12 +29,6 @@ Initial setup:
 
 . "$TEST_DIRECTORY"/lib-rebase.sh
 
-test_cmp_rev () {
-	git rev-parse --verify "$1" >expect.rev &&
-	git rev-parse --verify "$2" >actual.rev &&
-	test_cmp expect.rev actual.rev
-}
-
 set_fake_editor
 
 # WARNING: Modifications to the initial repository can change the SHA ID used
diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
index 34c86e5de6..6f489e20ee 100755
--- a/t/t3501-revert-cherry-pick.sh
+++ b/t/t3501-revert-cherry-pick.sh
@@ -100,4 +100,13 @@ test_expect_success 'revert forbidden on dirty working tree' '
 
 '
 
+test_expect_success 'chery-pick on unborn branch' '
+	git checkout --orphan unborn &&
+	git rm --cached -r . &&
+	rm -rf * &&
+	git cherry-pick initial &&
+	git diff --quiet initial &&
+	! test_cmp_rev initial HEAD
+'
+
 test_done
diff --git a/t/t3506-cherry-pick-ff.sh b/t/t3506-cherry-pick-ff.sh
index 51ca391e47..373aad623c 100755
--- a/t/t3506-cherry-pick-ff.sh
+++ b/t/t3506-cherry-pick-ff.sh
@@ -105,4 +105,12 @@ test_expect_success 'cherry pick a root commit with --ff' '
 	test "$(git rev-parse --verify HEAD)" = "1df192cd8bc58a2b275d842cede4d221ad9000d1"
 '
 
+test_expect_success 'chery-pick --ff on unborn branch' '
+	git checkout --orphan unborn &&
+	git rm --cached -r . &&
+	rm -rf * &&
+	git cherry-pick --ff first &&
+	test_cmp_rev first HEAD
+'
+
 test_done
diff --git a/t/t3507-cherry-pick-conflict.sh b/t/t3507-cherry-pick-conflict.sh
index c82f7210c4..223b98433c 100755
--- a/t/t3507-cherry-pick-conflict.sh
+++ b/t/t3507-cherry-pick-conflict.sh
@@ -11,12 +11,6 @@ test_description='test cherry-pick and revert with conflicts
 
 . ./test-lib.sh
 
-test_cmp_rev () {
-	git rev-parse --verify "$1" >expect.rev &&
-	git rev-parse --verify "$2" >actual.rev &&
-	test_cmp expect.rev actual.rev
-}
-
 pristine_detach () {
 	git checkout -f "$1^0" &&
 	git read-tree -u --reset HEAD &&
diff --git a/t/t3508-cherry-pick-many-commits.sh b/t/t3508-cherry-pick-many-commits.sh
index 340afc760d..4e7136b837 100755
--- a/t/t3508-cherry-pick-many-commits.sh
+++ b/t/t3508-cherry-pick-many-commits.sh
@@ -5,15 +5,11 @@ test_description='test cherry-picking many commits'
 . ./test-lib.sh
 
 check_head_differs_from() {
-	head=$(git rev-parse --verify HEAD) &&
-	arg=$(git rev-parse --verify "$1") &&
-	test "$head" != "$arg"
+	! test_cmp_rev HEAD "$1"
 }
 
 check_head_equals() {
-	head=$(git rev-parse --verify HEAD) &&
-	arg=$(git rev-parse --verify "$1") &&
-	test "$head" = "$arg"
+	test_cmp_rev HEAD "$1"
 }
 
 test_expect_success setup '
diff --git a/t/t3510-cherry-pick-sequence.sh b/t/t3510-cherry-pick-sequence.sh
index b5fb527b2e..7b7a89dbd5 100755
--- a/t/t3510-cherry-pick-sequence.sh
+++ b/t/t3510-cherry-pick-sequence.sh
@@ -24,12 +24,6 @@ pristine_detach () {
 	git clean -d -f -f -q -x
 }
 
-test_cmp_rev () {
-	git rev-parse --verify "$1" >expect.rev &&
-	git rev-parse --verify "$2" >actual.rev &&
-	test_cmp expect.rev actual.rev
-}
-
 test_expect_success setup '
 	git config advice.detachedhead false &&
 	echo unrelated >unrelated &&
diff --git a/t/t6030-bisect-porcelain.sh b/t/t6030-bisect-porcelain.sh
index 72e28ee535..3e0e15fb3e 100755
--- a/t/t6030-bisect-porcelain.sh
+++ b/t/t6030-bisect-porcelain.sh
@@ -676,9 +676,7 @@ test_expect_success 'bisect fails if tree is broken on trial commit' '
 check_same()
 {
 	echo "Checking $1 is the same as $2" &&
-	git rev-parse "$1" > expected.same &&
-	git rev-parse "$2" > expected.actual &&
-	test_cmp expected.same expected.actual
+	test_cmp_rev "$1" "$2"
 }
 
 test_expect_success 'bisect: --no-checkout - start commit bad' '
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 22a4f8fb64..fa62d010f6 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -602,6 +602,13 @@ test_cmp() {
 	$GIT_TEST_CMP "$@"
 }
 
+# Tests that its two parameters refer to the same revision
+test_cmp_rev () {
+	git rev-parse --verify "$1" >expect.rev &&
+	git rev-parse --verify "$2" >actual.rev &&
+	test_cmp expect.rev actual.rev
+}
+
 # Print a sequence of numbers or letters in increasing order.  This is
 # similar to GNU seq(1), but the latter might not be available
 # everywhere (and does not do letters).  It may be used like: