[PATCH v2 0/2] Fix regression in checkout -b

[Ben Peart <peartben@gmail.com>]

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From: Ben Peart <benpeart@microsoft.com>

The optimized `checkout -b` doesn’t typically create/update the index and
working directory.  Add a new test to detect the case when the call to
`checkout -b` is the first call after doing a `clone --no-checkout` and no
index exists.  In this specific case, well now make the call to
merge_working_tree() which will create the index and update the working
directory.

Also simplify and update the test cases based on the feedback provided by
Szeder and Junio.  A shout out to Johannes who diagnosed, fixed and patched
a bug that was preventing me from running the git test suite in the master
branch.

Base Ref: master
Web-Diff: https://github.com/benpeart/git/commit/55dd8602f5
Checkout: git fetch https://github.com/benpeart/git initial-checkout-v2 && git checkout 55dd8602f5


### Interdiff (v1..v2):

diff --git a/builtin/checkout.c b/builtin/checkout.c
index af6b5c8336..9c6e94319e 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -517,12 +517,6 @@ static int skip_merge_working_tree(const struct checkout_opts *opts,
 	if (core_apply_sparse_checkout && !checkout_optimize_new_branch)
 		return 0;
 
-	/*
-	 * We must do the merge if this is the initial checkout
-	 */
-	if (is_cache_unborn())
-		return 0;
-
 	/*
 	 * We must do the merge if we are actually moving to a new commit.
 	 */
@@ -598,6 +592,13 @@ static int skip_merge_working_tree(const struct checkout_opts *opts,
 	 * Remaining variables are not checkout options but used to track state
 	 */
 
+	 /*
+	  * Do the merge if this is the initial checkout
+	  *
+	  */
+	if (!file_exists(get_index_file()))
+		return 0;
+
 	return 1;
 }
 
diff --git a/t/t2018-checkout-branch.sh b/t/t2018-checkout-branch.sh
index c438889b0c..c5014ad9a6 100755
--- a/t/t2018-checkout-branch.sh
+++ b/t/t2018-checkout-branch.sh
@@ -200,13 +200,11 @@ test_expect_success 'checkout -B to the current branch works' '
 
 test_expect_success 'checkout -b after clone --no-checkout does a checkout of HEAD' '
 	git init src &&
-	echo hi > src/a &&
-	git -C src add . &&
-	git -C src commit -m "initial commit" &&
+	test_commit -C src a &&
 	rev="$(git -C src rev-parse HEAD)" &&
 	git clone --no-checkout src dest &&
 	git -C dest checkout "$rev" -b branch &&
-	test -f dest/a
+	test_path_is_file dest/a.t
 '
 
 test_done


### Patches

Ben Peart (2):
  checkout: add test to demonstrate regression with checkout -b on
    initial commit
  checkout: fix regression in checkout -b on intitial checkout

 builtin/checkout.c         | 7 +++++++
 t/t2018-checkout-branch.sh | 9 +++++++++
 2 files changed, 16 insertions(+)


base-commit: 77556354bb7ac50450e3b28999e3576969869068
-- 
2.19.1.gvfs.1.16.g9d1374d