[autoroller] All commits in updates(), only roll interesting ones.

recipe_engine/autoroll_impl/commit_list.py

 # Copyright 2017 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 from recipe_engine.fetch import CommitMetadata
 
 class UnknownCommit(KeyError):
   pass
 
 class CommitList(object):
   """A seekable list of CommitMetadata objects for a single repo.
 
   This can also be used to obtain the list of commits 'rolled so far' for the
   purposes of generating a changelist.
   """
 
   def __init__(self, commit_list):
     """
     Args:
       commit_list (list(CommitMetadata)) - The list of CommitMetadata objects to
       use.
     """
     assert commit_list, 'commit_list is empty'
     assert all(isinstance(c, CommitMetadata) for c in commit_list)
     self._commits = list(commit_list)
     self._cur_idx = 0
+    self._next_roll_candidate_idx = None
 
     # This maps from commit hash -> index in _commits.
     self._rev_idx = {}
 
     # This maps dep_project_id -> dep_commit -> set(idxs)
     self._dep_idx = {}
     for i, c in enumerate(commit_list):
       self._rev_idx[c.revision] = i
 
       for dep_project_id, dep in c.spec.deps.iteritems():
@@ skipping 25 matching lines @@
   def next(self):
     """Gets the next CommitMetadata without advancing the current index.
 
     Returns the next CommitMetadata or None, if there is no next CommitMetadata.
     """
     nxt_idx = self._cur_idx+1
     if nxt_idx >= len(self._commits):
       return None
     return self._commits[nxt_idx]
 
+  @property
+  def next_roll_candidate(self):
+    """Gets the next CommitMetadata and distance with roll_candidate==True
+    without advancing the current index.
+
+    Returns (CommitMetadata, <distance>), or (None, None) if there is no next
+      roll_candidate.
+    """
+    # Compute and cache the next roll candidate index.
+    nxt_idx = self._next_roll_candidate_idx
+    if nxt_idx is None or nxt_idx <= self._cur_idx:
+      nxt_idx = None
+      for i, commit in enumerate(self._commits[self._cur_idx+1:]):
+        if commit.roll_candidate:
+          nxt_idx = self._cur_idx + i + 1
+          break
+      self._next_roll_candidate_idx = nxt_idx
+
+    if nxt_idx is not None:
+      return self._commits[nxt_idx], nxt_idx - self._cur_idx
+    return (None, None)
+
   def advance(self):
     """Advances the current CommitMetadata by one.
 
     That is: CommitList.next becomes CommitList.current.
 
     Returns the now-current CommitMetadata (or None, if there was no next
       CommitMetadata).
     """
     ret = self.next
     if ret:
@@ skipping 90 matching lines @@
     Args:
       target_commit (str) - the commit to obtain the changelist for.
 
     Returns list(CommitMetadata) - The CommitMetadata objects corresponding to
       the provided target_commit.
 
     Raises:
       UnknownCommit if target_commit is not found.
     """
     return list(self._commits[:self._idx_of(target_commit)+1])