create_default_files(): don't set u+x bit on $GIT_DIR/config

Since time immemorial, the test of whether to set "core.filemode"
has been done by trying to toggle the u+x bit on $GIT_DIR/config,
which we know always exists, and then testing whether the change
"took".  I find it somewhat odd to use the config file for this
test, but whatever.

The test code didn't set the u+x bit back to its original state
itself, instead relying on the subsequent call to git_config_set()
to re-write the config file with correct permissions.

But ever since

    daa22c6f8d config: preserve config file permissions on edits (2014-05-06)

git_config_set() copies the permissions from the old config file to
the new one.  This is a good change in and of itself, but it
invalidates the create_default_files()'s assumption, causing "git
init" to leave the executable bit set on $GIT_DIR/config.

Reset the permissions on $GIT_DIR/config when we are done with the
test in create_default_files().

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/init-db.c

@@ -254,7 +254,8 @@ static int create_default_files(const char *template_path)
 		struct stat st2;
 		filemode = (!chmod(path, st1.st_mode ^ S_IXUSR) &&
 				!lstat(path, &st2) &&
-				st1.st_mode != st2.st_mode);
+				st1.st_mode != st2.st_mode &&
+				!chmod(path, st1.st_mode));
 	}
 	git_config_set("core.filemode", filemode ? "true" : "false");
 

t/t0001-init.sh

@@ -12,6 +12,13 @@ check_config () {
 		echo "expected a directory $1, a file $1/config and $1/refs"
 		return 1
 	fi
+
+	if test_have_prereq POSIXPERM && test -x "$1/config"
+	then
+		echo "$1/config is executable?"
+		return 1
+	fi
+
 	bare=$(cd "$1" && git config --bool core.bare)
 	worktree=$(cd "$1" && git config core.worktree) ||
 	worktree=unset