Executable.add_default_arg: multiple (#40801)

lib/spack/spack/fetch_strategy.py

@@ -773,8 +773,7 @@ def git(self):
             # Disable advice for a quieter fetch
             # https://github.com/git/git/blob/master/Documentation/RelNotes/1.7.2.txt
             if self.git_version >= spack.version.Version("1.7.2"):
-                self._git.add_default_arg("-c")
-                self._git.add_default_arg("advice.detachedHead=false")
+                self._git.add_default_arg("-c", "advice.detachedHead=false")
 
             # If the user asked for insecure fetching, make that work
             # with git as well.

lib/spack/spack/util/executable.py

@@ -35,9 +35,9 @@ def __init__(self, name):
         if not self.exe:
             raise ProcessError("Cannot construct executable for '%s'" % name)
 
-    def add_default_arg(self, arg):
-        """Add a default argument to the command."""
-        self.exe.append(arg)
+    def add_default_arg(self, *args):
+        """Add default argument(s) to the command."""
+        self.exe.extend(args)
 
     def add_default_env(self, key, value):
         """Set an environment variable when the command is run.

lib/spack/spack/util/git.py

@@ -24,7 +24,6 @@ def git(required: bool = False):
     # If we're running under pytest, add this to ignore the fix for CVE-2022-39253 in
     # git 2.38.1+. Do this in one place; we need git to do this in all parts of Spack.
     if git and "pytest" in sys.modules:
-        git.add_default_arg("-c")
-        git.add_default_arg("protocol.file.allow=always")
+        git.add_default_arg("-c", "protocol.file.allow=always")
 
     return git