177 lines
6.8 KiB
Python
177 lines
6.8 KiB
Python
# Copyright (c) 2018 Hewlett Packard Enterprise Development Company LP
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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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, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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#
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import git
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from fixtures_git import _utils
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class GitTree(object):
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"""Helper class to build a git repository from a graph definition
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Helper class to build a git repository from a graph definition of
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nodes and their parent nodes. A list of branches may be provided
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where each element has two members corresponding to the name and the
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target node it references.
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Supports unordered graphs, only requirement is that there is a commit
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defined with no parents, which will become the root commit.
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Root commits can specified by an empty list as the second member:
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('NodeA', [])
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Merge commits are specified by multiple nodes:
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('NodeMerge', ['Node1', 'Node2'])
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An '=' prefix can be used in front of one of the parents of a merge
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commit to indicate that the merge commit's tree should be copied
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directly from that parent ignoring any contributions from the other
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parents' trees (like what git enables with the '-s ours' merge
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strategy.
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This is used when needing to preserve history but not interested in
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the changes from the other branches. One tool that makes extensive
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usage of this is _git-upstream.
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E.g., the following will result in a merge commit 'C', with parents
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'P1' and 'P2', but will have the same tree as 'P1'.
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('C', ['=P1', 'P2'])
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The tree building code can handle a graph definition being out of
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order but will fail to find certain circular dependencies and may
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result in an infinite loop.
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Examples:
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[('A', []), ('B', ['A']), ('C', ['B'])]
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[('A', []), ('C', ['B']), ('B', ['A'])]
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.. _git-upstream: https://pypi.python.org/pypi/git-upstream
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"""
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def __init__(self, gitrepo, tree, branches):
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self.graph = {}
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self.gitrepo = gitrepo
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self.repo = gitrepo.repo
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self._build_git_tree(tree, branches)
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def _commit(self, node):
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p_node = _utils.get_node_to_pick(node)
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if p_node:
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self.repo.git.cherry_pick(self.graph[p_node], x=True)
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else:
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# standard commit
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self.gitrepo.add_commits(1, ref="HEAD",
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message_prefix="[%s]" % node)
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def _merge_commit(self, node, parents):
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# merge commits
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parent_nodes = [p.lstrip("=") for p in parents]
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commits = [str(self.graph[p]) for p in parent_nodes[1:]]
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if any([p.startswith("=") for p in parents]):
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# special merge commit using inverse of 'ours' by
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# emptying the current index and then reading in any
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# trees of the nodes prefixed with '='
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use = [str(self.graph[p.lstrip("=")])
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for p in parents if p.startswith("=")]
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try:
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self.repo.git.merge(*commits, s="ours", no_commit=True)
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except git.exc.GitCommandError as exc:
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if 'refusing to merge unrelated histories' in exc.stderr:
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self.repo.git.merge(*commits, s="ours", no_commit=True,
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allow_unrelated_histories=True)
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else:
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raise
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self.repo.git.read_tree(empty=True)
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self.repo.git.read_tree(empty=True)
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self.repo.git.read_tree(*use, u=True, reset=True)
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elif len(commits) < 2:
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# standard merge
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try:
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self.repo.git.merge(*commits, no_commit=True)
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except git.exc.GitCommandError as exc:
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if 'refusing to merge unrelated histories' in exc.stderr:
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self.repo.git.merge(*commits, no_commit=True,
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allow_unrelated_histories=True)
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else:
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raise
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else:
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# multi-branch merge, git is not great at handling
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# merging multiple orphaned branches
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try:
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self.repo.git.merge(*commits, s="ours", no_commit=True)
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except git.exc.GitCommandError as exc:
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if 'refusing to merge unrelated histories' in exc.stderr:
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self.repo.git.merge(*commits, s="ours", no_commit=True,
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allow_unrelated_histories=True)
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else:
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raise
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self.repo.git.read_tree(empty=True)
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self.repo.git.read_tree("HEAD", *commits)
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self.repo.git.checkout("--", ".")
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self.repo.git.commit(m="[%s] Merging %s into %s" %
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(node, ",".join(parent_nodes[1:]),
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parent_nodes[0]))
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self.repo.git.clean(f=True, d=True, x=True)
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def _build_git_tree(self, graph_def, branches=None):
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if branches is None:
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branches = []
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# require that graphs must have at least 1 node with no
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# parents, which is a root commit in git
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if not any([True for _, parents in graph_def if not parents]):
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assert "No root commit defined in test graph"
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for node, parents in _utils.reverse_toposort(graph_def):
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if not parents:
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# root commit
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self.repo.git.symbolic_ref("HEAD", "refs/heads/%s" % node)
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self.repo.git.rm(".", r=True, cached=True,
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with_exceptions=False)
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self.repo.git.clean(f=True, d=True, x=True)
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self.gitrepo.add_commits(1, ref="HEAD",
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message_prefix="[%s]" % node)
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# only explicitly listed branches should exist afterwards
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self.repo.git.checkout(self.repo.commit())
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self.repo.git.branch(node, D=True)
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else:
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# checkout the dependent node
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self.repo.git.checkout(self.graph[parents[0].lstrip('=')])
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if len(parents) > 1:
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# merge commits
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self._merge_commit(node, parents)
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else:
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self._commit(node)
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self.graph[node] = self.repo.commit()
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for name, node in branches:
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self.repo.git.branch(name, str(self.graph[node]), f=True)
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# return to master
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self.repo.git.checkout("master")
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def commits_from_nodes(self, nodes):
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return [self.graph[n] for n in nodes]
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