Add cmd_lines function which runs a command and returns output lines

hggitforge/__init__.py

@@ -29,6 +29,11 @@ def cmd(description, *args, **kwargs):
         raise
 
 
+def cmd_lines(*args, **kwargs):
+    output = check_output(*args, **kwargs)
+    return output.decode("utf-8").splitlines()
+
+
 def git_clone(path_url, destination):
     cmd(
         "Cloning Git fork repository", ["git", "clone", path_url, destination, "--bare"]
@@ -105,11 +110,11 @@ def _gfclone(git_fork_url, git_upstream_url, destination):
 
 
 def _gfpull(git_repo):
-    branches = check_output(
+    branches = cmd_lines(
         ["git", "branch", "--format=%(refname:lstrip=2)"], cwd=git_repo
     )
     git_pull_master(git_repo)
-    for branch in branches.decode("utf-8").splitlines():
+    for branch in branches:
         if branch != "master":
             try:
                 cmd(