Merge branch 'mh/refs-have-new'

Simplify the ref transaction API around how "the ref should be
pointing at this object" is specified.

* mh/refs-have-new:
  refs.h: remove duplication in function docstrings
  update_ref(): improve documentation
  ref_transaction_verify(): new function to check a reference's value
  ref_transaction_delete(): check that old_sha1 is not null_sha1
  ref_transaction_create(): check that new_sha1 is valid
  commit: avoid race when creating orphan commits
  commit: add tests of commit races
  ref_transaction_delete(): remove "have_old" parameter
  ref_transaction_update(): remove "have_old" parameter
  struct ref_update: move "have_old" into "flags"
  refs.c: change some "flags" to "unsigned int"
  refs: remove the gap in the REF_* constant values
  refs: move REF_DELETING to refs.c

1 files changed, 30 insertions, 0 deletions

diff --git a/t/t7516-commit-races.sh b/t/t7516-commit-races.sh
new file mode 100755
index 0000000000..f2ce14e907
--- /dev/null
+++ b/t/t7516-commit-races.sh
@@ -0,0 +1,30 @@
+#!/bin/sh
+
+test_description='git commit races'
+. ./test-lib.sh
+
+test_expect_success 'race to create orphan commit' '
+	write_script hare-editor <<-\EOF &&
+	git commit --allow-empty -m hare
+	EOF
+	test_must_fail env EDITOR=./hare-editor git commit --allow-empty -m tortoise -e &&
+	git show -s --pretty=format:%s >subject &&
+	grep hare subject &&
+	test -z "$(git show -s --pretty=format:%P)"
+'
+
+test_expect_success 'race to create non-orphan commit' '
+	write_script airplane-editor <<-\EOF &&
+	git commit --allow-empty -m airplane
+	EOF
+	git checkout --orphan branch &&
+	git commit --allow-empty -m base &&
+	git rev-parse HEAD >base &&
+	test_must_fail env EDITOR=./airplane-editor git commit --allow-empty -m ship -e &&
+	git show -s --pretty=format:%s >subject &&
+	grep airplane subject &&
+	git rev-parse HEAD^ >parent &&
+	test_cmp base parent
+'
+
+test_done