147 lines
4.4 KiB
Python
147 lines
4.4 KiB
Python
#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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# vim:ts=4:sw=4:softtabstop=4:smarttab:expandtab
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# Copyright (c) 2020 Kevin B. Hendricks, Stratford Ontario Canada
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#
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# Dulwich is dual-licensed under the Apache License, Version 2.0 and the GNU
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# General Public License as public by the Free Software Foundation; version 2.0
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# or (at your option) any later version. You can redistribute it and/or
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# modify it under the terms of either of these two licenses.
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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# You should have received a copy of the licenses; if not, see
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# <http://www.gnu.org/licenses/> for a copy of the GNU General Public License
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# and <http://www.apache.org/licenses/LICENSE-2.0> for a copy of the Apache
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# License, Version 2.0.
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"""
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Implementation of merge-base following the approach of git
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"""
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from collections import deque
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def _find_lcas(lookup_parents, c1, c2s):
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cands = []
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cstates = {}
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# Flags to Record State
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_ANC_OF_1 = 1 # ancestor of commit 1
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_ANC_OF_2 = 2 # ancestor of commit 2
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_DNC = 4 # Do Not Consider
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_LCA = 8 # potential LCA
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def _has_candidates(wlst, cstates):
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for cmt in wlst:
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if cmt in cstates:
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if not (cstates[cmt] & _DNC):
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return True
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return False
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# initialize the working list
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wlst = deque()
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cstates[c1] = _ANC_OF_1
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wlst.append(c1)
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for c2 in c2s:
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cstates[c2] = _ANC_OF_2
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wlst.append(c2)
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# loop until no other LCA candidates are viable in working list
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# adding any parents to the list in a breadth first manner
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while _has_candidates(wlst, cstates):
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cmt = wlst.popleft()
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flags = cstates[cmt]
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if flags == (_ANC_OF_1 | _ANC_OF_2):
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# potential common ancestor
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if not (flags & _LCA):
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flags = flags | _LCA
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cstates[cmt] = flags
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cands.append(cmt)
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# mark any parents of this node _DNC as all parents
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# would be one level further removed common ancestors
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flags = flags | _DNC
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parents = lookup_parents(cmt)
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if parents:
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for pcmt in parents:
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if pcmt in cstates:
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cstates[pcmt] = cstates[pcmt] | flags
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else:
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cstates[pcmt] = flags
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wlst.append(pcmt)
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# walk final candidates removing any superceded by _DNC by later lower LCAs
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results = []
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for cmt in cands:
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if not (cstates[cmt] & _DNC):
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results.append(cmt)
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return results
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def find_merge_base(repo, commit_ids):
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"""Find lowest common ancestors of commit_ids[0] and *any* of commits_ids[1:]
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Args:
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repo: Repository object
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commit_ids: list of commit ids
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Returns:
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list of lowest common ancestor commit_ids
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"""
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if not commit_ids:
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return []
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c1 = commit_ids[0]
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if not len(commit_ids) > 1:
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return [c1]
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c2s = commit_ids[1:]
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if c1 in c2s:
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return [c1]
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parents_provider = repo.parents_provider()
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return _find_lcas(parents_provider.get_parents, c1, c2s)
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def find_octopus_base(repo, commit_ids):
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"""Find lowest common ancestors of *all* provided commit_ids
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Args:
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repo: Repository
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commit_ids: list of commit ids
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Returns:
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list of lowest common ancestor commit_ids
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"""
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if not commit_ids:
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return []
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if len(commit_ids) <= 2:
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return find_merge_base(repo, commit_ids)
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parents_provider = repo.parents_provider()
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lcas = [commit_ids[0]]
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others = commit_ids[1:]
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for cmt in others:
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next_lcas = []
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for ca in lcas:
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res = _find_lcas(parents_provider.get_parents, cmt, [ca])
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next_lcas.extend(res)
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lcas = next_lcas[:]
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return lcas
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def can_fast_forward(repo, c1, c2):
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"""Is it possible to fast-forward from c1 to c2?
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Args:
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repo: Repository to retrieve objects from
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c1: Commit id for first commit
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c2: Commit id for second commit
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"""
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if c1 == c2:
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return True
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# Algorithm: Find the common ancestor
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parents_provider = repo.parents_provider()
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lcas = _find_lcas(parents_provider.get_parents, c1, [c2])
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return lcas == [c1]
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