ENH: Add some features that the crawler needs

datalad/tests/utils.py

@@ -1827,21 +1827,35 @@ def newfunc(*args, **kwargs):
     return newfunc
 
 
-def get_branch_commits(repo, branch=None):
+def get_branch_commits(repo, branch=None, limit=None, stop=None):
     """Return commit hexshas for a branch
 
     Parameters
     ----------
     branch: str, optional
       If not provided, assumes current branch
+    limit: None | 'left-only', optional
+      Limit which commits to report.  If None -- all commits (merged or not),
+      if 'left-only' -- only the commits from the left side of the tree upon
+      merges
+    stop: str, optional
+      hexsha of the commit at which stop reporting (matched one is not
+      reported either)
 
     Yields
     ------
     str
     """
+    cmd = ['rev-list']
+    if limit == 'left-only':
+        cmd.append('--left-only')
     if not branch:
         branch = repo.get_active_branch()
-    return repo.call_git_items_(['rev-list', branch])
+    cmd.append(branch)
+    for r in repo.call_git_items_(cmd):
+        if stop and stop == r:
+            return
+        yield r
 
 
 #