rework: make set_milestones more testable

Author: MrKevinWeiss

riot_release_manager.py

@@ -123,11 +123,32 @@ def update_branch(repo_dir, remote, branch):
         stderr=subprocess.DEVNULL
     )
 
+
+def _merge_commits_to_prs(log: str):
+    """Extracts PR numbers from merge commits in a git log.
+
+    Args:
+        log: git log
+
+    Returns:
+        list of PR numbers
+
+    >>> log = 'Merge #19495\\n'
+    >>> log += 'drivers/lsm303agr: Rename deprecated unit G to GForce\\n'
+    >>> log += 'Merge #19499 #19500\\n'
+    >>> log += 'sam0/usbdev: partial revert of #17086\\n'
+    >>> prs = _merge_commits_to_prs(log)
+    >>> assert prs == [19495, 19499, 19500]
+    """
+    merge_lines = [line for line in log.splitlines() if line.strip().startswith('Merge #')]
+    return [int(line) for line in re.findall(r"#([0-9]+)", '\n'.join(merge_lines))]
+
+
 def get_merged_prs_with_git(repo_dir, since):
     log = subprocess.run(git(repo_dir) + ["log", "--merges", "%s..HEAD" % since],
                          capture_output=True, text=True).stdout
-    merge_lines = [line for line in log.splitlines() if line.strip().startswith('Merge #')]
-    return [int(line) for line in re.findall(r"#([0-9]+)", '\n'.join(merge_lines))]
+    return _merge_commits_to_prs(log)
+
 
 def get_tags(repo_dir, remote):
     subprocess.run(git(repo_dir) + ["fetch", "--tags", remote])