script/cibuild,t: always enable test count locks

In commit 9b73c80 of PR git-lfs#3125 the
GIT_LFS_LOCK_ACQUIRE_DISABLED environment variable was introduced
for use with our test suites.  When this variable was set to the value
"1", it indicated to the lfstest-count-tests test utility that it
should skip creating a test_count.lock file before updating the
test_count file we use to track the number of active test suites.

This was done because the lfstest-count-tests program had a bug
which prevented it from deleting the lock file, causing subsequent
invocations of the program to be unable to exclusively create it
again.  As this bug was not resolved at the time, the choice was
made to work around the problem by skipping the creation of a
lock file altogether on Windows.

This change was also made in conjunction with the addition of another
environment variable, GIT_LFS_NO_TEST_COUNT, in commit
c591ff7 of the same PR.  That variable
is also set only on Windows, and stops the setup() and shutdown()
shell functions defined in our t/testhelpers.sh script from calling
the lfstest-count-tests program.

As we have now resolved the underlying problem in the lfstest-count-tests
utility, in a prior commit in this PR, we can now remove both of
these environment variables and the test suite features they control.

We start by removing support for the GIT_LFS_LOCK_ACQUIRE_DISABLED
environment variable from the lfstest-count-tests utility, and
changing our script/cibuild script so it no longer sets the variable.

We can also remove the environment variable from the list of those
we unset before running certain tests.  We had to introduce this
behaviour in commit aca1aff of
PR git-lfs#3808, when we migrated our CI test suite to GitHub Actions.
However, we will no longer need to unset these variables as we will
now never set them at all, and they will have no effect if they
were set.

Author: chrisd8088

script/cibuild

@@ -10,7 +10,6 @@ if [[ $UNAME == MINGW* || $UNAME == MSYS* || $UNAME == CYGWIN* ]]; then
   X=".exe"
   WINDOWS=1
   export GIT_LFS_NO_TEST_COUNT=1
-  export GIT_LFS_LOCK_ACQUIRE_DISABLED=1
 fi
 
 # Build git-lfs-transfer from scutiger.

t/cmd/lfstest-count-tests.go

@@ -170,10 +170,6 @@ var (
 // acquire acquires the lock file necessary to perform updates to test_count,
 // and returns an error if that lock cannot be acquired.
 func acquire(ctx context.Context) error {
-	if disabled() {
-		return nil
-	}
-
 	path, err := path(lockFile)
 	if err != nil {
 		return err
@@ -205,10 +201,6 @@ func acquire(ctx context.Context) error {
 // release releases the lock file so that another process can take over, or
 // returns an error.
 func release() error {
-	if disabled() {
-		return nil
-	}
-
 	path, err := path(lockFile)
 	if err != nil {
 		return err
@@ -279,16 +271,6 @@ func path(s string) (string, error) {
 	return p, nil
 }
 
-// disabled returns true if and only if the lock acquisition phase is disabled.
-func disabled() bool {
-	s := os.Getenv("GIT_LFS_LOCK_ACQUIRE_DISABLED")
-	b, err := strconv.ParseBool(s)
-	if err != nil {
-		return false
-	}
-	return b
-}
-
 // fatal reports the given error (if non-nil), and then dies. If the error was
 // nil, nothing happens.
 func fatal(err error) {

t/t-env.sh

@@ -8,7 +8,7 @@ git config filter.lfs.clean = "git-lfs clean -- %f"'
 
 unset_vars() {
     # If set, these will cause the test to fail.
-    unset GIT_LFS_NO_TEST_COUNT GIT_LFS_LOCK_ACQUIRE_DISABLED
+    unset GIT_LFS_NO_TEST_COUNT
 }
 
 begin_test "env with no remote"

t/t-worktree.sh

@@ -9,7 +9,7 @@ git config filter.lfs.clean = "git-lfs clean -- %f"'
 
 unset_vars () {
     # If set, these will cause the test to fail.
-    unset GIT_LFS_NO_TEST_COUNT GIT_LFS_LOCK_ACQUIRE_DISABLED
+    unset GIT_LFS_NO_TEST_COUNT
 }
 
 begin_test "git worktree"